title: Oceans tropical

text:
Tropical oceans encircle Earth in an equatorial band between the Tropic of Cancer (23.5° North latitude) and the Tropic of Capricorn (23.5° South latitude).* The central portions of the Pacific and Atlantic Oceans and most of the Indian Ocean lie in the tropics. The warm tropical oceans play a critical role in regulating Earth's climate and large-scale weather patterns. Much of the planet's biological diversity resides in the tropics, and the global distribution of species and ecosystems depends on oceanographic and atmospheric processes that occur in the equatorial oceans.
Heat from the Sun drives global circulation of Earth's oceans and atmosphere. Much of that critical solar radiation initially falls on the tropics, where the Sun lies almost directly overhead for the entire year. The water temperature of tropical oceans thus typically exceeds 20°C (68°F) and stays relatively constant throughout the year. Particularly intense radiation directly over the equator evaporates seawater and forms a mass of very warm, humid tropical air that subsequently rises and cools as it flows north and south. Because cool air holds less moisture than warm air, the water vapor quickly condenses into clouds and falls as precipitation. Heavy, warm, yearround rains are a hallmark of Earth's tropical regions. Fragile, biologically diverse ecosystems such as rainforests and coral reefs thrive in the warm, wet tropics.
Uneven heating of the sea surface between the tropics and the poles creates heat-driven convection currents in the atmosphere and oceans.* Vertical circulation in the tropical oceans also affects the distribution of heat and biological nutrients throughout the global ocean. In general, surface water sinks at downwellings where surface currents flow toward a continental coastline, or where two surface currents converge. Deep ocean water rises to the surface at upwellings where surface currents flow away from land, or where surface currents diverge. Tropical downwellings transfer heat and nutrients to the deep-ocean circulation system. At tropical upwellings, cool, oxygen-rich and nutrient-rich deep water supports abundant marine life. Because normal tropical currents flow from east to west, downwellings often occur along the east coasts of tropical continents, and upwellings are common along their west coasts. In the Pacific Ocean, for example, an upwelling off the west coast of South America usually feeds extremely productive fisheries of coastal Peru and Ecuador, and a downwelling in Polynesia forces warm, oxygen-depleted water into the deep ocean.
Tropical upwellings support huge populations of microscopic plants and animals called phytoplankton and zooplankton. Plankton, in turn, feed many species of fish and other marine life, and humans who depend on fish for food. Tropical fisheries account for about half of the world's fish catch, even though tropical oceans represent only 0.01 percent of Earth's ocean volume.
Coral reefs are another well-recognized feature of tropical oceans. The seas surrounding tropical islands and low-latitude continental shelves away from major river deltas are ideal for coral reef formation. Over millennia, very large reefs have formed in the Caribbean Sea, and especially in the southwest Pacific Ocean. For example, the Great Barrier Reef of northeastern Australia covers thousands of square kilometers.
see also Carbon Dioxide in the Ocean and Atmosphere; Climate and the Ocean; Corals and Coral Reefs; El NiÑo and La NiÑa; Ocean Currents; Ocean Mixing; Plankton; Weather and the Ocean.
Brian D. Hoyle
and Laurie Duncan
Open University Course Team. Ocean Circulation. Oxford, U.K.: Pergamon Press, 1993.
Press, Frank, and Raymond Siever. Understanding Earth. New York: W.H. Freeman and Company, 2001.
Ross, David A. Introduction to Oceanography. New York: Harper Collins College Publishers, 1995.
Turk, Daniela, Michael J. McPhoden, Antonio J. Busalacchi, and Marlon R. Lewis. "Remotely Sensed Biological Production in the Equatorial Pacific." Science 293 (July 20, 2000): 471–474.
* See "Climate and the Ocean" for an illustration of circulation zones.
* See "Climate and the Ocean" for an illustration of the tropical zones.


tier: cub

shelf: home-craft

title: Gold sequin long prom dress sweetheart beaded sparkle prom evening dresses nv246

text:
1.If you are unable to zoom in to the pictures on mobile, please save them to your phone for closer look. 2.Leave the correct color number in cart note. 3.We have more colors. If you can not find the color you want. Please contact us. 4.Please be noted there maybe tiny color differences caused by different fabric and monitor display setting.
Hollow to floor
Couldn't load pickup availability
Product :nv246 Fabric：as picture shown Sleeves：sleeveless Color：As Picture,Custom color Back Details: as picture shown
I ordered this dress in a size 16, custom color number 14. It took two and a half weeks to arrive after ordering. This dress is amazing, and it fits true to size. It is a lot of fabric though, so ironing that skirt took me like two hours lol. It has a medium layer of satin as the skirt, so I needed to wear a hoop skirt underneath to give it volume. The hoops were still semi-visible through the fabric, though, so I will say that. The chest is padded and thick, so no need to wear a bra underneath if that's what you prefer. Overall, the quality of the dress is amazing, and communication of the custom color I wanted went great. Would totally buy from this seller again!
We bought this dress for my daughter’s junior prom. It was the only dress she found that she loved. Sadly, with the covid lockdown, it was not able to be shipped out in time for her prom. She came up with an adorable suit ensemble to wear instead! She decided she could wear the dress next year. When the dress finally did arrive, she and I were amazed at the beauty of the dress and the obvious care that went into making it. The bodice/corset is a little bit big, but hopefully with some slight alterations, it will be perfect. Thank you for making this beautiful dress for my daughter! Thanks also for the great email communication. Wishing you healthier days ahead!
Shipping had me nervous but they made sure everything came in time and that I remained calm . I will order with them again if there’s another event happening. It’s not a scam , dress look exactly how I wanted it to be although the lace won’t be your skin color but you can get that take care of . Great communication
The shipping and making is closer to the 5-6 week range but it was well worth the wait, and it was very nicely hand made and fit my daughter perfectly! I can’t express how pleased I was with my purchase!
I absolutely love this dress i thought that it was going to look cheap but its stunning. the slit isn't that high but i was going to fix it to make it lower anyways so i actually loved that!!! thank y'all so much for such a beautiful dress im amazed. Cant wait to wear it to prom and show off the curves it gives me!!


shelf: history-culture

title: The Raid: Redemption

text:
The Raid: Redemption
aka Serbuan maut
Written and directed by Gareth Evans
One man, one building, hundreds of potential opponents. A police raid gone wrong, way wrong, sets up The Raid: Redemption, as the cops are wasted, leaving only a few stragglers to be slowly picked off. There will be no rescue, no backup, thanks to layers of corruption so thick they have to make the sequel about them. But no one counted on Rama being the best fighter in the universe.
The Raid was hyped as the most actiony action film that ever actioned, and then it actions some more. Well, I don’t know about all that, but it was pretty actiony. The fighting is intense and hardhanded, and quickly devolves to hand to hand combat. As the surviving cops’ numbers shrink and they are slowly hunted, the tension mounts up, keeping pace with the action.
The biggest problem with The Raid is the lack of good character development. The rudimentary structures are there, but aside from falling into some templates, the characters aren’t that rounded out. Rama is the good cop and son because he just is. Andi says he was a disappointment and is better at being a criminal…because he says so. If anything, only Mad Dog and the corrupt Wahyu have any sort of build beyond their templates. And while we don’t really need everyone to be fully nuanced, it’s nice to have some depth occasionally.
But still, the fighting is furious, the action is intense, and The Raid is one martial arts film you will watch again.


shelf: civic-law

title: Derek carr fools jets first ballot hall famer disguise

text:
The New York Jets are going to be surprised when this “first ballot Hall of Famer” pulls off his mask and it’s just Derek Carr.
This feels like an old episode of Scooby Doo or something, one where the bad guy gets unmasked at the end of the show and says something like “I would have gotten away with it if it wasn’t for you pesky kids.” Only this time there’s somehow no mask, only Derek Carr and a description that makes us shake our heads every time we hear it.
In case you missed the Carr-related news of the day, the New York Jets are putting on a full-court press for the services of the veteran quarterback. Not only are they wining and dining him in hopes of convincing him to sign, but they’re also making grand descriptions of his future—and we’re pretty sure they’re unfounded.
Dianna Russini of ESPN has word of the Jets’ recent visit with Carr and it’s a doozy. We’ll let her tell you first-hand.
“They told him he’s a great quarterback,” said Russin ctrong young skill guys, the explosive run game—they ran through top to bottom of why Derek Carr can step in here and take this team not just to the playoffs but to the Super Bowl. They made it really personal, too. They said, ‘We believe if you come to New York and win, you can be a first-ballot Hall of Famer.’ So they went full in on Derek Carr to let him know they really want him to play for the New York Jets.”
That first ballot HOF player bit feels over the top for a quarterback who couldn’t do anything for the Raiders during his long stint with the team. With a sparkling 63-79 record, perhaps the Jets are dreaming of that period second place finish in the AFC East. Better yet is having a whole assortment of Carrs at a team’s disposal to use as they see fit.
If Derek Carr is a first-ballot Hall of Famers, then we can only Romeo Crennel likely won Head Coach of the Year in 2012 and we somehow missedit.


shelf: science-engineering

title: What type of air filter should i get

text:
One of the most important parts of your home’s air-circulation system is the HVAC filter. We change them out every so often, but there might not be a whole lot of thought put into what type of filter you’re using. It’s worked so far, so why wouldn’t it work some more?
You’re not wrong. If the HVAC filter you’ve been using hasn’t given you any problems, then it makes sense to go with what you know. But did you know you’ve got a wealth of options to choose from? Each one offers pros and cons, so you’ll be able to find the one that works the best for you. Let the AC experts at Acree Plumbing, Air & Electric help you out!
What Matters is the MERV
On every type of air filter, regardless of the material it’s made out of, you’ll see a rating on the package. It’ll be a number, usually anywhere between 1 and 20, and it lets you know how effective an air filter is at screening out pollutants.
This number is called the MERV rating – or the Minimum Efficiency Reporting Value. It’s a simple way to understand which filters are more effective than others.
Which One Is Best?
There are a few different types of filters, each of which has a different MERV range than the others.
- Fiberglass: These are on the low end of the spectrum with a MERV range of 1-3. They use a simple fiberglass structure to screen things, but they’re incredibly cheap – for good reason. The fiberglass material wasn’t ever really designed to be effective at preventing allergens from getting in – they were invented primarily to protect an HVAC unit from being damaged from larger particles.
- Pleated: One of the most common types of air filters. Pleated filters are still inexpensive with a MERV range of 4-6, but the material that makes up the pleats is better at removing smaller materials from the air. However, not all HVAC units are necessarily going to work better with a filter that has a higher MERV rating. If your unit can’t generate the power to push through a finer screen, your AC efficiency will actually decrease!
- High-Efficiency Filters: With a MERV rating from 12-16, high-efficiency filters are used in places that need incredibly sterile and clean environments, like hospitals. Unless your home has specific health-related conditions, you likely won’t need to use one of these.
- HEPA Filters: The best of the best, HEPA filters can have a MERV rating as high as 20. These are almost certainly too finely constructed to work with a residential HVAC system, so we’d steer clear of these.
Acree Plumbing, Air & Electric: Tampa’s Air Efficiency Experts
If you’re due for a new air filter and you’re thinking about making a switch, give us a call! Our AC experts can help you pick the right one for you and your family. The next time you ask “what type of air filter should I get?” is the last time. We’ve got you covered!
Give Acree Plumbing, Air & Electric a call at (813) 530-9061 to see what we can do for you!


tier: grizzly

shelf: software-docs

title: Plugin Tag: wp-api

text:
Plugin Tag: wp-api
Extends the WP REST API using JSON Web Tokens Authentication as an authentication method.
Exposes Advanced Custom Fields Endpoints in the WordPress REST API
Stores meta data (i.e plugin settings) from the meta field of a WP REST API posts or pages POST creation call in the created page or post meta data.
WordPress plugin to log REST API requests and responses
Extends WordPress WP REST API with new routes pointing to WordPress menus.
A simple plugin that adds a password reset facility to the WordPress REST API using a code. The process is a two step process:
Plugs Advanced Custom Fields (ACF) data into the WordPress JSON API (WP-API).
This plugin include all available taxonomy attributes into the WordPress REST API (v2) without additional API requests.
Returns Yoast post or page metadata in a normal post or page request.
Enable caching for WordPress REST API and increase speed of your application
Run advanced searches via the WordPress REST API and SearchWP.
WP Custom REST API Generator plugin enables the user to show/hide varied meta information of Posts in WordPress REST API.
Query multiple post types using /wp/v2/posts
Wordpress is a good content mangement system for building websites, but it will be better if you build like mobile apps,
Adds menu endpoints to core WP REST API.
This plugin include all existing terms into separate WordPress REST API (v2) endpoint.
Adds a key and gutenberg block schema within the WordPress REST API
This plugin show all relations between existing post types and attached to them terms (taxonomies) in separate WordPress REST API (v2) endpoint.
Force WP REST API endpoints to only be served over HTTPS.


shelf: health

title: Dear Dr. Samson,

text:
Dear Dr. Samson,
My entire family received flu shots before last winter. In the subsequent two months we have had the stomach flu a couple of times and the flu with sore throats and headaches at least once. What good are the flu shots if they don’t protect us?
“Flu” is the most commonly misused term in the daily practice of clinical medicine. It is used as a generic diagnostic term. Unfortunately, patients take it as a specific entity. In reality, the term “influenza” means an infection of the respiratory tract by a specific virus. It causes a pneumonia picture with high fever, headache, generalized muscle aches and severe cough. It is not responsive to antibiotics, unless there is a secondary infection by bacteria.
The object of a “flu shot” is to provoke the patient’s immune system to make antibodies against the particular influenza organisms in the vaccine. If the strains of influenza in the vaccine are the same ones that are causing a “flu” outbreak, then recipients of the shot are protected. If the influenza virus causing an outbreak was not included in the vaccine used the patient is left vulnerable to the disease. Fortunately, this is not a common occurrence.
To answer your question specifically, the “flus” that you are referring to are not influenza, but various types of viral illnesses
These infectious agents are not included in the influenza vaccine. If the symptoms are gastrointestinal, the condition should be referred to as acute viral gastroenteritis instead of the “stomach flu.” It certainly is not wrong to use the generic flu terms as long as everyone understands the difference between true influenza and what is called the “flu” in the non-specific sense.
Whether a patient should receive a “flu shot” is an individual decision that must be made with the help of a person’s physician. It demands assessment of the patient’s past and current medical status as well as the predicted severity of the coming flu season.
One easily forgets having the “flu” but remembers suffering through a bout of true influenza for a long time.


shelf: finance

title: ArdorComm Media News Network

text:
ArdorComm Media News Network
June 5, 2025
Media mogul Byron Allen is taking steps to divest his expansive portfolio of broadcast television stations, signaling a major strategic shift for his company, Allen Media Group.
The company announced on Monday that it has enlisted the investment firm Moelis & Co. to manage the potential sale of its 28 broadcast stations. These stations, affiliated with major networks like ABC, NBC, CBS, and Fox, operate in 21 markets across the United States.
Allen Media Group has invested more than $1 billion over the past six years to acquire these stations. According to a statement from Allen, the decision to consider a sale follows “numerous inquiries and written offers” from prospective buyers interested in acquiring much of the portfolio.
If finalized, the sale would place Allen Media Group among several media owners currently reevaluating their station holdings. Sinclair Broadcast Group and Apollo Global Management, which owns Cox Media Group, have reportedly explored similar moves, indicating a broader trend of consolidation and divestiture in the broadcast space.
Allen Media Group said the potential sale would help ease its financial burdens by significantly cutting down its debt. Earlier this year, the company restructured a $100 million credit facility, although S&P Global Ratings maintained a “junk” rating on the company due to ongoing liquidity and debt concerns.
Reports have also surfaced regarding late payments from Allen Media Group to major networks—sometimes delayed by up to 90 days and amounting to tens of millions of dollars. The company has not publicly addressed these allegations. Additionally, there have been reports of workforce reductions at some of the stations.
Byron Allen, who started his media journey as a comedian before founding Entertainment Studios in the early 1990s, has aggressively expanded his media footprint over the past decade. In 2019, he established Allen Media Group Broadcasting and has since pursued a number of high-profile acquisitions. His name has surfaced in connection with multi-billion-dollar bids for Paramount Global, Disney’s broadcast assets including ABC, and BET Media Group.
Now, as he weighs the future of his broadcast holdings, industry observers will be watching closely to see what comes next for one of media’s most ambitious entrepreneurs.
Photo Credit: Patrick T. Fallon / Afp / Getty Images


shelf: education

title: Safety in our School

text:
Safety in our School
Our school is committed to safeguarding and promoting the welfare of all of its pupils; keeping
our pupils safe is our number one priority. We recognise that some children may be especially vulnerable to abuse and that children who are abused or neglected may find it difficult to develop a sense.
The school pays full regard to DfES guidance ‘Keeping Children Safe in Education’. We ensure that all appropriate measures are applied in relation to everyone who works in the school who is likely to be perceived by the children as a safe and trustworthy adult including e.g. volunteers and staff employed by contractors. Safer recruitment practice includes scrutinising applicants, verifying identity and academic or vocational qualifications, obtaining professional and character references, checking previous employment history and ensuring that a candidate has the health and physical capacity for the job. It also includes undertaking interviews and, where appropriate, ISA and Criminal Records Bureau checks.
Designated Safeguarding Lead: James Rogers (Head Teacher)
Deputy Designated Safeguarding Leads: Kerry Redman (Deputy Head Teacher)
Safeguarding Governor: Sarah Stefano
Designated First Aiders: Elaine Hart, Michele Crawley
Business Manager: Tina Lee
Site Manager: Terry Portway
School Office: 01277 810218 firstname.lastname@example.org
Child Protection and Safeguarding
If you have concerns regarding a child regarding a child in school, then contact James Rogers, the Designated Safeguarding Lead in the school as soon as possible. In his absence, please contact Kerry Redman, the Deputy Designated Safeguarding Lead. If you wish to make a child protection referral because you are worried about a child you can contact the Children and Families Hub on 0345 6037627.
If you are concerned about the conduct of a member of staff following something you have observed or a disclosure, you must report this to the Head teacher (or Deputy Head teacher) in the absence of the Head teacher). If your concern is about the Head teacher you must report this to the Chair of Governors.
Visitors to school
In line with our safeguarding procedures, all visitors must sign in and wear their visitors’ badges at all times. Visitors not wearing their badges will be challenged and asked to return to reception, to sign in or leave the premises.
Everyone on-site must familiarise yourself with the fire safety instructions which are displayed in every room, and the site of the nearest fire exits. In the event of a fire alarm sounding (a continuous bell) please leave the building by the nearest available exit. The muster point is on far side of the school playground. Visitors to the school reception area should evacuate through the front door of the school and muster on the playground.
Health and safety
Any health and safety concerns on site should be brought to the immediate attention of the Site Manager (Mr Terry Portway) and/or the Head teacher
Strangers on site
If you witness anyone behaving in a suspicious or concerning manner on or near to the school site, please bring these to the immediate attention of the school office/ a member of the school staff.


title: Florence Chest of Drawer

text:
Florence Chest of Drawer
Introducing the Solid Wood Florence Chest of Drawers with Six Drawers
Discover the indispensable Solid Wood Florence Chest of Drawers from Chuk Chuk Villa Furniture. This cabinet showcases a captivating blend of solid wood and rattan, radiating elegance and sophistication throughout your home.
Light and Bright Design
Embrace the light and bright style of this cabinet, which seamlessly combines rattan and wood. Its natural allure adds a touch of refinement to any room. With six spacious sliding drawers, it's the ideal chest for your bedroom, accommodating all your clothing and essentials with ease.
Versatile Storage Solution
The Florence Chest of Drawers transcends boundaries, making it suitable for various living spaces. Its minimalist design harmonizes effortlessly with any decor, whether contemporary or traditional. The amalgamation of rattan and wood lends an organic essence, elevating your room's ambiance.
Ample Space, Smooth Operation
Equipped with six spacious drawers, this cabinet offers abundant storage for all your belongings. The sliding mechanism ensures seamless access, while the sturdy build promises longevity. Invest in the Florence Chest of Drawers for enduring quality and functionality.
Cherished for Years
The Florence Chest of Drawers is an investment in lasting utility and beauty. With its enduring style and construction, it's a furniture piece that will be cherished for years to come. Elevate your home's storage and organization with the Florence Chest of Drawers from Chuk Chuk Villa Furniture today!
Quality, Style, Unmatched Prices
Made in Solid Wood
Transform Your House into a Home with Our Customer Favorites. Experience the Joy of Comfort and Style, Loved by Thousands of Homes Across the Country. Where Quality Meets Satisfaction.
Distinctive Characteristics of Our Wood Types
Each wood species tells its own story through rich tones and natural grain patterns—crafted to complement your space and stand the test of time.
Teak exudes exotic elegance with warm honey to deep brown hues and rich grains. Over time, it develops a timeless silver-grey patina, ideal for luxurious interiors.
Sheesham features striking contrasts and deep tones ranging from golden brown to purplish hues. Its natural grains make every piece one-of-a-kind.
Mango wood brings a bold look with its dramatic textures and tones—from deep blond to chocolate brown. A sustainable choice with distinct character.
Acacia showcases golden-brown tones with stunning linear grains. Loved for its strength and elegance, it adds organic charm to contemporary spaces.


title: Rekha starrer umrao jaan to re release in restored version on june 27 70881

text:
“Umrao Jaan”, the cult classic 1981 film starring Rekha in the lead role, is set to re-release across PVR INOX theatres in a restored 4K version on June 27.
Rekha essayed the role of Amiran, a courtesan-poetess in the film, which was directed by Muzaffar Ali. The period musical drama also earned the actor a National Award for ‘Best Actress’ in 1982.
The film has been restored by NFDC-NFAI. It will be screened as a part of PVR INOX’s Timeless Classics initiative, which curates landmark films that have shaped Indian cinema’s artistic legacy, according to a press release
In a statement, Rekha said the character remains a part of her.
“‘Umrao Jaan’ is not just a film I acted in, she lives within me, breathes through me, even now,” she said in a statement.
“At the time, none of us could have imagined the timelessness of the film, the way it would gently etch itself into the soul of Indian cinema. To see it return to the big screen is like watching an old love letter being opened by a new generation. My heart is full,” she added.
Ali said he is “thrilled” about the film re-releasing in theatres again.
“‘Umrao Jaan’ was not just a film, it was a journey into the soul of a lost culture, a forgotten tehzeeb. Through her pain, poetry, and grace, we tried to resurrect the elegance of an era where love and longing spoke in verse.
“I had actors who brought a lot of heft to their characters, and then there was Rekha, who lived Umrao Jaan and truly immortalised it. I am thrilled that the film is back on the big screen for a whole new generation to discover a time and culture that is very much a part of our being,” he said.
“Umrao Jaan” revolved around Rekha’s character, a young woman who gets kidnapped and sold into a brothel where she becomes a courtesan named Umrao Jaan. It is based on Mirza Hadi Ruswa’s 1899 Urdu novel “Umrao Jaan Ada“.
The film is also remembered for its iconic songs such as “Dil Cheez Kya Hai, “In Aankhon Ki Masti“, and “Justuju Jiski Thi“.


title: Landlord tenant law

text:
DISCLAIMER: This website does not provide legal advice. While we attempt to make sure the information is accurate, we recommend that you consult a lawyer for legal advice.
Any and all information, notices, and resources from www.ericstevenlaw.com does not constitute legal advice or an attorney/client relationship and are for general information purposes and use only. Information and notices provided are specific to laws in the state of Washington and not any other state. Eric Steven is a licensed attorney in the state of Washington, and a member of the Washington State Bar Association.
Steven Law Office does not guarantee that all information, notices, and resources neither are current, nor do the Law Office of Steven Law Office warrant that all information on www.ericstevenlaw.com will be suitable for a particular purpose. Users should be aware that legal advice should be given by a licensed attorney who practices in necessary fields of law and has a firm understanding of specific and particular information regarding each individual case. Users should not use and or rely on the information from www.ericstevenlaw.com without seeking professional legal counsel.
Please do not send confidential information, documents, or attachments to Steven Law Office without first contacting the office. Commercial or third party use is strictly forbidden without the express written consent of Steven Law Office. No claim is made to original government works.
The Washington Court of Appeals issued an opinion with great impact on the manner of serving notices to tenants. You are required to serve a notice on each adult tenant named on your lease and/or subtenant in occupancy to acquire unlawful detainer (eviction) jurisdiction.
1.) Delivering copies of the Notice personally to each adult tenant named on the lease and each adult subtenant in occupancy. If any tenant or subtenant is absent, always hand a copy of the Notice for that individual to someone at the leasehold if possible.
You must attempt to deliver the Notice by Personal Service to each adult tenant and subtenant. If no individual can be found at the leasehold then go directly to posting and mailing of the Notice. However, I always want you to post and mail in addition to personal delivery.
2.) Posting a separate copy of the Notice for each individual adult tenant and/or subtenant on the front door of the leasehold premises. Your lease may also require sliding a copy of the Notice under the door.
3.) Mailing a separate copy of the Notice to the residence of each individual adult tenant, and/or subtenant. Mailing should be done by regular, first class mail. If your lease requires certified mail, then mail by certified mail in addition to mailing by first class. Mailing must be done from the county where the leasehold premises is situated. You must actually deposit the notice with the postal service, do not place the envelope in the mail box directly.


title: Fly ash bricks and their importance

text:
Fly ash bricks are revolutionizing the construction industry with their eco-friendly, durable, and cost-effective features. These bricks, made from fly ash, lime, gypsum, and sand, offer a sustainable alternative to traditional clay bricks while enhancing structural integrity. Rajratan Industries, a leading manufacturer and supplier of PAC Pallets for brick blocks and pavers, supports the production and transportation of high-quality fly ash bricks.
Why Fly Ash Bricks Are Important
Fly ash bricks reduce environmental waste by repurposing industrial byproducts, contributing to cleaner and greener construction practices.Durability and Strength
These bricks are known for their higher compressive strength and better resistance to water seepage, making them ideal for long-lasting structures.Cost Efficiency
Their lighter weight reduces construction costs, from transportation to labor, while maintaining high performance.Thermal Insulation
Fly ash bricks offer excellent thermal insulation, ensuring energy-efficient buildings and reduced cooling and heating costs.Versatile Application
They are suitable for residential, commercial, and industrial projects, catering to a wide range of construction needs.
Why Choose Rajratan Industries?
As a trusted supplier of PAC Pallets for bricks, blocks, and pavers, Rajratan Industries ensures:
- High-Quality Pallets: Designed for durability and smooth handling in manufacturing processes.
- Customizable Solutions: Tailored to meet specific production needs.
- Reliability: On-time delivery and expert customer support for a seamless experience.
Rajratan Industries is committed to delivering the best materials and solutions for your construction requirements. Build sustainable and efficient projects with fly ash bricks and PAC pallets.
Contact Us Today
Rajratan Industries – Leading the Way in Construction Solutions
Phone: +91 9685927927
Monday to Saturday: 10 AM to 6 PM.


tier: polar

text:
I am in the process of using the --eraseinstall switch with starttoinstall as documented here:
I use the suggested switches "/Applications/Install macOS High Sierra.app/Contents/Resources/startosinstall" ‑‑eraseinstall
‑‑newvolumename "Macintosh HD" --agreetolicense
I receive the following message Error: Could not get license agreement.
Anybody else seeing this issue or have a fix?
It might be a typo in your post but I see you forget the & at the end of the command.
"/Applications/Install macOS High Sierra.app/Contents/Resources/startosinstall" --eraseinstall --newvolumename "Macintosh HD" --agreetolicense &
Are you using the full Apple OS installer, or the "shell" installer? I had the 800 error when I tried this originally and that was because I was using a copy of the installer from my SUS. You can tell the difference between the two because the shell installer is about 15 MB (and it downloads assets on command) and the full installer is about 5 GB. Only the latter actually has the contents to do this. I provided Apple with feedback asking them to remove the command line features from the shell installer.
@ooshnoo check out the size of the installer that downloaded. If it's not the 5/6GB download you may have a stub that doesn't include the full contents of the macOS installer. Check out installinstallmacos.py as a failproof way to always download a full installer without relying on the Mac App Store or Software Update Servers (also gives you a list of all available macOS installers, not just the most recent shipping macOS version).


title: Japan provides jpy 500 million medical grant to sri lanka

text:
Japan has provided JPY 500 million worth of modern Japanese medical equipment to Sri Jayewardenepura General Hospital to strengthen the hospital capabilities to combat Non-Communicable Diseases (NCDs) and enhance the social and humanitarian development in Sri Lanka, which has been highly affected due to present dire economic conditions.
On August 18, Ambassador Hideaki Mizukoshi signed an Exchange of Note for the grant assistance, the Embassy of Japan in Colombo said in a statement.
Sri Jayewardenepura General Hospital was constructed in 1983 with the grant aid from the Japanese government as a token of appreciation and friendship to former President Mr. J. R. Jayewardene for his generous encouragement of Japan’s return to the international community at the San Francisco Peace Conference.
Augmenting the historical relationship, Japan will provide latest equipment such as CT angiography, catheter surgical equipment, transplantation devices, ophthalmology equipment, as well as establishing the new dental ward, to enhance treatment and surgical capabilities for NCDs including cancer, stroke, and diabetes, while reducing the rate of blindness and caries in Sri Lanka.
NCDs patients account for over 80% of all deaths in Sri Lanka and they tend to be at higher risk of severe symptoms and death when infected with COVID-19.
Furthermore, the current economic crisis poses a significant risk of increased NCDs due to deteriorating health and nutritional status to many citizens. “We hope this assistance will improve diagnosis and treatment of NCDs and help reduce related mortality and incidence in Sri Lanka, especially in the Western Province, the embassy said further.
“At this historic milestone of the 70th anniversary of the diplomatic relationships between Japan and Sri Lanka, we believe that Sri Jayewardenepura General Hospital will become another landmark to represent the close bilateral relationship.”
The statement read that Japan remain committed to help overcome this economic crisis together as a long-standing development partner of Sri Lanka.


title: Amazon and quickbooks announce team up to simplify finances for sellers

text:
Small business owners and third-party sellers have a new reason to celebrate: Amazon and Intuit’s popular QuickBooks accounting software are teaming up to streamline the financial management process for sellers on the e-commerce giant’s platform. The partnership aims to simplify bookkeeping, tax preparation, and overall financial operations, which is welcome news for the millions of sellers navigating the complexities of running a business via Jeff Bezos’s online retail giant.
Here’s everything you need to know about this collaboration and what it means for small business owners using Amazon.
Amazon has announced a partnership with Intuit’s QuickBooks to offer enhanced financial tools for third-party sellers. Per CNBC, the new tools are expected to be available by “mid-2025” for all Amazon sellers. The integration is designed to:
Automatically sync sales data from Amazon into QuickBooks.
Simplify expense tracking by categorizing fees, commissions, and other charges directly within the software.
Provide better insights into profitability and cash flow.
This collaboration is part of Amazon’s broader initiative to support third-party sellers, who accounted for 60% of its $400 billion in global sales last year, according to the same CNBC report.
Managing finances can be one of the most challenging aspects of running an e-commerce business. For Amazon sellers, tracking fees, taxes, shipping costs, and inventory expenses often requires juggling multiple tools and platforms.
With the Amazon-QuickBooks integration, sellers can:
Save Time on Bookkeeping
The direct data sync between Amazon and QuickBooks eliminates manual entry, reducing the risk of errors and freeing up time for business growth.
Streamline Tax Preparation
Automatically categorized expenses and sales reports make tax season less stressful. Sellers can easily pull profit and loss statements to prepare for filing.
Gain Better Financial Visibility
QuickBooks’ real-time insights allow sellers to track their cash flow, profitability, and expenses at a glance, empowering better financial decisions.
The partnership brings several features that will benefit Amazon sellers directly:
Automated Data Import: Sales, fees, and refunds from Amazon sync automatically with QuickBooks.
Expense Categorization: Seller fees, shipping costs, and other Amazon-related expenses are automatically categorized for easier financial reporting.
Real-Time Reporting: Access up-to-date financial information, including cash flow and profit margins.
Tax Tools: Generate reports and summaries to simplify quarterly and annual tax filings.
The timing of this partnership is significant. As e-commerce continues to grow post-pandemic, many small businesses have turned to platforms like Amazon to reach larger audiences. However, with growth comes complexity—especially in managing finances.
This move reflects Amazon’s recognition of the logistical challenges many of its sellers face and the brand’s commitment to providing tools that make running an online business easier.
Among the many benefits of the QuickBooks-Amazon partnership are:
A Simpler Tax Season: Connecting your Amazon accounts to QuickBooks will make for easier reconciliation and tax preparation for tax professionals.
More Accurate Data: Automated imports reduce discrepancies, leading to cleaner books.
Improved Collaboration: Real-time data access allows accountants and clients to work together more efficiently.
Amazon sellers can integrate QuickBooks by navigating to their Seller Central account and following these steps:
Go to the Partner Network section and select QuickBooks.
Follow the prompts to link your Amazon account to QuickBooks.
Configure your settings to sync data automatically.
Lawrence Glass/iStock Editorial via Getty Images
For those new to QuickBooks, Intuit offers setup assistance to ensure a smooth transition. Our office can also help you move smoothly into using QuickBooks. Simply call us to get started.
The Amazon-QuickBooks partnership represents a significant step forward for small business owners and third-party sellers, offering tools that simplify financial management. This integration promises to make 2025 – and beyond – more productive and financially sound for Amazon’s massive seller base.
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text:
JMU Giving Day on March 21; University seeks to set new record
JMU NewsDonors to James Madison University can unlock an extra $200,000 for student scholarships by topping last year’s JMU Giving Day record of 5,095 gifts. The fourth-annual JMU Giving Day runs midnight to midnight on Thursday, March 21, at JMU Giving Day, and also includes campus activities and events for alumni throughout the country and right here in Harrisonburg during the 24-hour period.
Last year, 5,095 gifts raised more than $700,000 in just 24 hours so that students can enjoy a more meaningful Madison Experience. The stakes are high this year to set a new record. John (’88) and Karen (’93) Rothenberger have pledged $200,000 toward the Centennial Scholars program, which provides scholarships for Virginia residents with financial need, if Dukes can beat the previous number of gifts received during the day.
“Over the last three years, the excitement around JMU Giving Day has grown and ignited a spirit of philanthropy in the Madison community,” said Gretchen Armentrout, Director of Annual Giving at JMU. “The gifts we receive help all of our academic programs and make a positive impact where it matters most… with our students.”
James Madison University is currently in the midst of its second-ever comprehensive fundraising campaign, with goals of $200 million in total funds raised and 65,000 donors engaged by June 2022. Unleashed: The Campaign for James Madison University will help set the course for the university’s future. The campaign stands at $134 million, with contributions from more than 46,000 members of the JMU community.
Supporters are also encouraged to follow along and join the fun on social media by searching and using #JMUGivingDay.
Media are invited to come by fundraising headquarters or visit us at one of the many stops that the Giving Day bus will be making throughout campus. Contact Caitlyn Read at email@example.com for details.


title: Offbeat bites irish pocket pies

text:
Chef’s note: With the arrival of fall, we typically start eating heavier foods and use the oven a lot more. These cute Irish-inspired pocket pies are perfect for the season, and surprisingly substantial for their size, making one or two ideal to eat for lunch or dinner. They are fairly easy to make as well, and can be assembled ahead of time. For a future meal, you can place them in the freezer for an anytime snack, even on a weeknight. The recipe yields about eight pies. You will invariably have extra filling, but if you don’t want to waste it, you can eat the extra filling like chili.
1 to 2 tablespoons of vegetable oil
2 cups of shredded green cabbage (I used angel hair coleslaw)
½ lb of red potatoes, scrubbed then diced
1 large carrot, peeled
1 lb of minced or ground beef sirloin or lamb
About 1 cup of fresh or thawed frozen peas
1 cup of water
3 tablespoons of tomato paste
½ teaspoon of Worcestershire sauce
½ teaspoon of dried thyme
Salt and pepper, to taste
All-purpose flour, for dusting and rolling
2 9-inch pie crusts
Egg wash (one egg beaten with 2 tablespoons of water)
Heat oil over medium heat, add carrots, potatoes, and cabbage. Cook for about 7 to 9 minutes, until beginning to brown.
Add beef, and cook until no longer pink, about 5 minutes.
Stir in tomato paste, thyme, worcestershire sauce, peas, and water. Cover and cook for about 15 minutes or until potatoes are tender.
Mash mixture lightly with fork – try not to damage the peas too much. Season to taste with salt and pepper. Cool completely.
Preheat oven to 400F. Prepare two greased baking sheets.
Roll out one pie crust into a large, thin, square piece of dough approximately 12 or 13 inches across. Cut into 4 smaller equal squares. Repeat for the second pie crust.
Spoon filling onto each square, leaving plenty of room to fold the crust and form a border. Fold the crust over and bring the edges to meet.
Crimp the edges with a fork. Slit 3 vents into each pie. (At this point, if you want to freeze the pies, you would freeze them until solid, then wrap them in foil. They keep, frozen, for up to two months.) Brush each pie with egg wash.
Bake for 12 minutes, or until golden brown, rotating the baking sheet halfway through. If baking from frozen, bake for about 30 minutes. Let the pies cool for 5 minutes before serving.
All photos by Lauren Quinn


title: 26295 rogue ones tarkin vfx won t replace actors ilm promises

text:
John Knoll worked double duty on Rogue One: The chief creative officer at ILM first came up with the story for the new Star Wars spin-off film and then oversaw the blockbuster’s enormous visual effects department.
Rogue One was perhaps the most complicated Star Wars film from a VFX perspective to date. ILM has paved the way in developing cutting edge technologies over the last 40 years, coming a long way from the miniatures and models they rigged up on the fly in a warehouse during the production of A New Hope. But having all the resources in the world was actually a potential handicap, since Rogue One had to recreate the look and feel of the 1977 original. Knoll and his team put a lot of work into making sure Star Wars fans didn’t notice a single difference. With the film being a critical and financial success, Knoll spoke to Inverse about how they were able to solve the many complicated problems set before them and the limits of the technology they have pioneered.
There’s been a lot of talk about the way you recreated Peter Cushing and Carrie Fisher via motion capture and face replacement. How far do you think we are from not even needing an actor to put the face on? Can it be full animation?
Oh, you need an actor. I want to clarify that it’s not so much that that’s a CG character. Tarkin was played by Guy Henry. We cast a really good actor who played that role on set. I think a way to think of it is — the way we were thinking about it — is that you were casting an historic figure in a movie. And there are historic figures who you don’t know what they look like, and you get away [with] casting anyone you think is appropriate for it. And then there are historic figures that we’re very familiar with their image, whether you’re doing Nelson Mandela or John F. Kennedy. So that narrows down the actors you’re able to cast in that role. Often, some kind of effort is made to make that actor look more physically like the person they’re playing, whether it’s with makeup or full-on prosthetics.
What we did was not conceptually any different than doing something like that. We cast an actor who played the Tarkin role for us, and rather than using makeup to transform the appearance, we use computer graphics.
So you never think there will be a moment where you don’t need a live actor at all?
Well, the acting needs to come from somewhere.
There are CG-animated characters.
But I would say Pixar is not a conspiracy to get rid of actors. The actors are still very much involved. In the case of the animated picture, the animators are the actors. They’re making all those choices about performance. In this case, by partnering with Guy Henry as the character, he was making all those acting choices. The work we do afterwards is really one of interpreting his performance and making sure it stays on model and that it works well on the Tarkin character.
Did it help that he was stationary a lot? Tarkin stands straight and gives orders. Would it be harder if he had been an action hero?
No, it’d have been easier. The more they moved, the harder it is to pin them down and get a good look down at them. If they’re just standing there and talking reasonably close to the camera, you get more opportunity to examine the fine details of what makes a person really believable as a human being.
Doing face replacement on a stunt performer in an action scene, that’s something we’ve done pretty significantly on a lot of projects. A lot of people don’t notice it’s being done. It’s a lower bar than a close-up performance. A quiet acting moment is always going to be harder to do than a bloody battle or some other kind of action sequence.
You had to recreate a lot of things from the original movies via new technology, not just people. And in the prequels, things didn’t look old, and it was set before A New Hope. How did you capture that grittiness in a way that the prequels weren’t able to?
Some of it is passage of time — the tools have gotten a lot better. And it was also very deliberate, knowing it had to be very close to the look and feel of Episode IV. The overriding philosophy was to try to match how you remember Episode IV more than how it may actually have been. In terms of things like lighting design and shot design, it actually doesn’t match that well. But we pulled all the things that are your salient memories of those places and vehicles and managed to bring back that memory, so hopefully they can feel true and matches right up.
Technology has changed, so the things that were physical prop models in A New Hope are now made digitally. What was the hardest thing to accurately recreate?
One of the things I was keen to do was really illustrate the scale of the Death Star. It’s supposed to be 100 miles in diameter, and there are very few shots in the original that really show you how big that was. So we designed a shot when Krennic’s shuttle leaves the Death Star. It’s not quite a Powers of Ten shot, but you see his shuttle that just left the docking bay in the equatorial trench, and the camera keeps pulling back and tilting up. I was pretty pleased with how that turned out and I think it gave you a pretty good sense of how big that object really is.
That proved to be a really hard shot to do. We are depicting a scale of a Death Star that hadn’t been shown before. In the original film, it was shown as a spherical model, and a really tight close-up with those modular tiles. But we’re showing a scale halfway in between, and really marrying the aesthetics of all of those, that was a tricky thing to get right.
So how’d you do it?
For a lot of modelers and matte painters and art departments it was really going to [original production designer] Ralph McQuarrie school. We studied a lot of his design work to see how he did what he did. He painted the original three foot model of the Death Star, and there was a language to the line work that he did. He did a matte painting that was sort of a middle scale view. It’s in a couple of shots, to try to bridge the medium and close angles. A lot of paneling that he put into that matte painting, they seem random, but it really isn’t. There’s a very subtle and sophisticated design language in there that we referred to over and over again. As people were taking cracks at trying to show what some of the panels should look like — “This series of panels is four and a half miles tall, what level of detail should be in it?” — I kept pointing them to this McQuarrie painting. I [always] loved his work, but I have a newer and more profound respect for the brilliance for his design.
In A New Hope, we only see the Death Star obliterate a planet from space; we’re almost disconnected. In Rogue One we see the damage from the ground level, and it looks like a nuclear explosion. Was that parallel done on purpose?
Yeah, some of the larger themes in the film are about the morality and ethics of a weapon of mass destruction like that. A nuclear weapon infantry is not an outlandish idea to introduce here. Obviously, the big difference is you never saw the Death Star firing down from the view of a planet’s surface. Previously, it had been depicted at full power, where it just completely obliterates a planet. But this idea of doing a low-power hit that destroys just a localized area seemed like an intriguing thing to be able to see from the ground level. You’d think any massive release of energy like that would have a lot in common with nuclear testing.
This interview has been edited for brevity and clarity.


text:
Two Powerful Armenian Men Sentenced for Fraud Scheme
On November 28, 2012, a significant legal case unfolded, leading to the sentencing of two influential Armenian men involved in a large-scale fraud scheme. This article delves into the background, investigation, trial, and sentencing of these individuals.
1. The Allegations
The case revolved around allegations of a sophisticated fraud scheme, with the accused individuals accused of orchestrating a complex financial fraud operation spanning multiple countries. Their actions were said to have defrauded numerous victims of substantial amounts of money.
2. The Investigation
The investigation into the alleged fraud scheme was extensive, involving law enforcement agencies and financial experts from multiple jurisdictions. The investigation revealed a network of financial transactions, shell companies, and complex money laundering efforts designed to conceal the ill-gotten gains.
3. The Legal Process
The legal process involved the arrest and subsequent trial of the two accused individuals. Legal authorities worked tirelessly to build a case against them, bringing forth evidence that included financial records, witness testimonies, and digital traces of their fraudulent activities.
4. The Trial
The trial of the two powerful Armenian men was closely watched by legal experts, the media, and the public. The prosecution presented a compelling case, highlighting the scale and sophistication of the fraud scheme. The accused individuals had a legal defense team that sought to challenge the evidence and provide an alternative narrative.
5. Verdict and Sentencing
The culmination of the trial was the verdict and subsequent sentencing. The court found the two individuals guilty of their involvement in the fraud scheme, concluding that they had exploited financial systems and defrauded innocent victims. As a result, they were sentenced to significant prison terms and ordered to pay restitution to the victims.
6. Impact and Implications
The sentencing of these powerful Armenian men had several significant implications:
a. Deterrence: The case sent a strong message that even individuals with considerable influence and resources would be held accountable for their fraudulent actions.
b. Justice for Victims: The victims of the fraud scheme finally received justice through the legal process, with the restitution helping to recover some of their losses.
c. Legal Precedent: The case established a legal precedent for dealing with complex financial fraud schemes, offering guidance for future investigations and prosecutions.
d. Strengthening Legal Systems: The successful resolution of this case demonstrated the effectiveness of legal systems in combating financial crimes and protecting the interests of the public.
The sentencing of the two powerful Armenian men in the 2012 fraud scheme case was a significant legal milestone. It showcased the determination of legal authorities to bring perpetrators of financial fraud to justice, regardless of their influence or resources. This case served as a reminder that the rule of law prevails, and those who engage in fraudulent activities will ultimately be held accountable for their actions.
On November 28, 2012, the US Attorney’s Office for the Central District of California stated that Angus Brown, aka “Homicide,” and Arman Sharopetrosian, aka “Horse,” received additional prison sentences for operating a identity theft scheme out of the Avenal State Prison.
The two men and other Armenian Power gang members worked with African-American street gang members and bribed co-conspirators at banks in order to gain control of bank accounts. The scheme caused at least $8 million in losses.
United States District Judge David O. Carter said it was one of the most sophisticated fraud schemes he’s seen in his time as a judge.
Angus Brown was serving a prison term for identity theft at the time of his arrest, and Arman Sharopetrosian was serving a 10-year sentence for shooting at a car and carrying a concealed weapon.
During the scheme, Brown and Sharopetrosian were able to steal bank information from mostly elderly victims and forged signatures of the victims. Checks worth large amounts of money were then deposited in bank accounts set up the conspirators. Recruited bank employees identified accounts and victims that were less likely to notice their identities were stolen.
During the case, prosecutors stated: “[The defendants’] express purpose was to target bank customers with large-value accounts who were not proficient in checking up on their accounts via the Internet [and] sought to use that information to plunder the victims’ life savings.”
Sharopetrosian was found guilty of bank fraud conspiracy, four counts of bank fraud, and seven counts of aggravated identity fraud. Brown pleaded guilty to bank fraud conspiracy, bank fraud, and 17 counts of aggravated identity theft.
20 defendants were named in the indictment, and most of the defendants will be sentenced in the next couple of months. Some of the defendants have already received 51 months in prison.
Source: Federal Bureau of Investigation


tier: kodiak

title: 2956

text:
Due to the combination of low density and excellent mechanical properties, carbon fibers (CFs) are one of the most promising reinforcers for polymer composites, especially in the fields of lightweight application [
3]. Such composites have been extensively utilized as structural materials in the aeronautic and automotive industries [
4]. Additionally, CF-reinforced polymer composites can be applied as antifriction materials [
6], as thermal conductive materials for heat exchangers and the thermal management of compact electronic units [
8], as electromagnetic shielding materials [
10], as sensors for structural health monitoring [
12], as ballistic protection materials [
13], as high-strength self-healing materials [
16], as materials for additive manufacturing [
CF-reinforced polymer composite characteristics depend strongly on the shape of the fibers and their location in the polymer matrix. Short CF-reinforced composites are suitable materials for tribological and electromagnetic shielding applications [
20]. The formation technology of such composites is cheap and easy enough [
22]; short CFs can be distributed in a polymer matrix uniformly or in an oriented manner. Short CF-filled polymers exhibit good mechanical properties [
23]; however, the excellent mechanical properties of CFs in polymer matrices cannot be realized completely in such composites. Thus, to achieve the mechanical characteristics required for high-performance structural application, continuous fibers are used for reinforcement.
Among the various types of continuous CFs, 2D CF fabrics are most commonly used as reinforcers for polymer composites designed for structural applications. Various types of CF fabrics are used in polymer composites; however, most applications of this kind are based on woven fabrics [
3]. Twill weave is one of the most commonly used weave CF structures, providing optimal mechanical characteristics for polymer-based composites [
27]. Moreover, twill weave CFs are widely utilized as the model object in theoretical works [
29], and can be a suitable object to design new polymer-based composites.
Currently, most CF-reinforced composites used in a wide range of industries, including aerospace, wind turbines, sports equipment, and the automotive industry, are based on thermoset polymers such as epoxy resin. The wide application of such composites creates a problem of their recycling; the irreversible cross-linked structure of cured thermoset polymers results in significant difficulties in the recovery of the CFs and the thermosetting polymer, since they cannot be melted, remoulded, reprocessed, or re-crosslinked into solid polymers. The effective recycling of CF-reinforced thermosetting polymers is a now serious problem, requiring an elaboration of complex processing technologies, including thermal, mechanical, and chemical treatments [
32]. Therefore, the elaboration of GF-reinforced composite materials with matrices based on easily recyclable thermoplastic polymers is being actively investigated. Thermoplastic-based composites show considerably higher static fracture toughness compared with thermoset (epoxy) composites [
3]. Additional advantages of thermoplastics are their unlimited shelf life, low curing duration, the ability to correct defects and damage by reheating, the possibility of reforming defective products [
33], high environmental resistance, and high chemical resistance, including to aviation fuels and oils [
In recent years, thermoplastic-based CF-reinforced composites have been elaborated and investigated widely [
34]. High-performance polymers are of particular interest among thermoplastics due to their high thermal stability and mechanical properties. Polyethersulfone (PES) is a superior performance engineering plastic with a high glass transition temperature Tg of 225 °C and an operating temperature up to 180 °C. PES possesses several advantages, including high toughness, the possibility to produce and form complex shapes, good antifriction properties, high modulus and strength, good fatigue resistance and dimensional stability, good fire retardancy, and chemical and radiation resistance.
As well as other high-performance polymers, PES is widely used as a toughening modifier for the epoxy matrix in CF-reinforced composites. The addition of PES allows for the significant improvement of interlaminar fracture toughness in epoxy-based CF-reinforced composites in comparison with composites containing no PES [
38]. Moreover, the addition of temperature-resistant PES to epoxy matrices can increase the fire resistance of CF-reinforced composites [
39]. In addition to epoxy-based composites, it has been reported that an addition of PES to the poly(phthalazinone ether sulfone ketone) thermoplastic matrix reduces the melting viscosity of the matrix polymer and improves the properties of the CF-reinforced composite, including interlaminar fracture toughness and flexural strength [
A significant number of papers on CF-reinforced PES-based composites have been published in recent decades; however, most of them relate to composites containing short or unidirectional CFs. In [
42], the mechanical and tribological properties of PES reinforced with short CFs and short glass fibers (GFs) are investigated. It was observed that the addition of both CF and GF increased the mechanical properties of PES, but the effect was higher in case of CF-reinforced PES. In terms of the tribological characteristics, a positive effect was observed only for CF-reinforced composites, and the addition of GF resulted in an increase in the friction coefficient magnitude [
41]. In [
42], a positive synergetic effect of the simultaneous reinforcement of PES with both short CFs and short GFs on the tensile/flexural strength and the wear resistance of the composites was observed. In [
43], the mechanical properties of PES reinforced with aligned (oriented) short CFs were studied; it was shown that fracture of such composites occurred only after the formation of a dense network of internal cracks. PES reinforced with chaotically oriented short CFs showed a good concentration stability of tensile strength and a high effectiveness of electromagnetic interference shielding [
44]. In [
45], the rheological characteristics of PES reinforced with short CFs were studied to develop the optimal parameters of such composites’ additive manufacturing.
As it is known, since CF surfaces are chemically inert, the surface modification of CF is required to improve fiber adhesion with polymers. One of the modification methods consists of surface coating CF with epoxy resin [
47]; it has been found that coating short CFs with phenol formaldehyde resin can simultaneously improve the tensile and flexural characteristics of PES-based composites [
47]. Another method of modification is surface coating short CFs with graphite oxide, which can provide enhanced mechanical properties [
49] and significantly improve the dimensional stability of PES-based composites in wide temperature range [
Unidirectional CF-reinforced composites are suitable objects to investigate the interface interactions between polymer matrices and reinforcers [
53]. The comparison of the mechanical properties of several thermoplastic matrices, including PES reinforced with unidirectional CF, has shown that the nature of the polymer matrix significantly affects the interfacial shear strength value [
52]. In [
53], two types of PES with differential molecular weight were used as matrices in CF-reinforced composites. It was shown that PES molecular weight has nearly no effect on the flexural modulus and shear strength value, whereas the increase in molecular weight of the matrix polymer results in a significant rise in flexural strength and interlamellar fracture toughness. As the interface interactions are strongly affected by chemical bonding, the effects of unidirectional CF surface modification on PES-based composite properties have been studied. In [
54], the influence of CF surface modification by thermal oxidation and by epoxy resin coating on the properties of unidirectional CF-reinforced PES is studied. It was found that the interfacial shear strength value of the composites was higher in the case of the epoxy resin modification of CF. The modification of the CF surface by carboxylic [
55] and polyamic [
56] acids has also been reported as an effective way to improve interfacial adhesion in PES-based composites reinforced with unidirectional CF.
Unfortunately, there are only a few papers on CF fabric-reinforced PES-based composites. In [
57], it is reported that unidirectional CF fabric-reinforced PES showed excellent antifriction properties in comparison with epoxy resin-based composites. In [
60], PES reinforced with twill weave CF fabrics treated with nitrogen and nitrogen oxygen cold plasma was investigated; it was found that the plasma treatment of CF resulted in an improvement in the tribological and mechanical properties of composites.
It is known that, due to the less permeable structure of CF fabrics, the polymer melt impregnation technique is not effective for the formation of composites with strong adhesion between the fibers and the matrix. For instance, in [
58], the melt impregnation of twill weave CF with PES with various molecular weights was studied. It was observed that the mechanical properties of the obtained composited improved with a decrease in PES molecular weight, i.e., with an increase in the PES melt flow index. This means that composite properties in this case are limited by poor fiber/polymer adhesion, restricting the mechanical properties of polymers with higher molecular weight in composites formed by melt impregnation. To achieve better adhesion on the fiber/polymer interface, the polymer solution impregnation method can be used. Cyclopentanone [
53] and dichloromethane [
60] have been used as solvents for PES to form PES/CF composites. Recently [
63], we used N-methyl-2-pyrrolidone as a solvent to obtain polysulfone-based composites reinforced with CF fabrics. In the present study, an elaborated technique is used to produce PES-based composites.
Thus, the purpose of this study is to develop a method of obtaining PES-based composite materials reinforced with carbon fabrics using solution technology, and to investigate the properties of the obtained materials. Moreover, since the interfacial interaction between the phases of the composites must be sufficient to provide good mechanical and thermophysical properties, the influence of the surface modification of carbon fibers on the properties of the obtained composites is studied.
2. Materials and Methods
Twill weave carbon fabric marked by 3K-1200-200 with a specific weight of 200 g/m
2 and 3000 filaments in one thread (HC Composite, Moscow, Russia) was used as the reinforcement material. Ultrason E2020 P SR Micro polyethersulfone with a density of 1.37 g/cm
3, a melt flow index of about 7.0 to 8.7 g/10 min, and a viscosity number of 59 in the form of powder (BASF, Ludwigshafen, Germany) was used as the matrix. For the proper impregnation of carbon fibers without breaking the reinforcement structure, PES powder was dissolved in N-2-methylpyrrolode (Eastchem, Changzhou, China) in a concentration of 20 wt. %. This method of impregnation has been considered as sufficient by some researchers [
40]. Dissolution was conducted at room temperature, using a magnetic stirrer. The concentration was chosen from the best correlation between viscosity and the lower content of solvent. Moreover, impregnation with the solution of the aforementioned concentration allowed the impregnation of the fibers relatively quickly, with an even distribution of matrix.
To remove the solvent from the matrix of the composite material, drying for 4 h at a temperature of 100 °C was conducted. The time and temperature of drying process were chosen as a result of thermogravimetric analysis (TGA). TGA was performed with TA Instruments Q600 (TA Instruments Inc., New Castle, DE, USA). During the experiment, samples were heated in alumina crucible to temperatures of 80, 100, and 120 °C, with a heat rate of 10 °C/min in a flow of air. The results of experiment are shown in
Figure 1. The TGA analysis shows that at the temperature of 100 °C, after 70 min of the experiment, almost all solvent was evaporated from the sample. Therefore, we dried the prepreg sheets for 4 h or more in order to guarantee the absence of solvent in the prepreg sheets.
Obtained by the molding of sliced prepregs at 350 °C for 30 min under a pressure of 10 MPa; samples of the composite materials with fiber contents of 70, 60, 50, and 40 wt. % (marked as 70/30, 60/40, 50/50, and 40/60, respectively) were cut to a testable shape. The mold with the samples was cold in the atmosphere of air. These molding conditions are commended as best for PES by Ultrason.
Figure 2 shows the scheme for obtaining of the composite material.
Samples with thicknesses of 2 mm and 1 mm were used for the three-point bend test and the tensile strength test, respectively. These tests were performed according to the DIN EN ISO 14125-2011 and ISO 527:2021 standards, respectively. The width of the samples was about 10 mm. In both cases, a traverse speed of 10 mm/min was maintained. The adhesion between the matrix and the reinforcement material was learned by the ASTM D 3846-08 (2015) interlaminar shear test. To provide the interlaminar shear, specimens of special geometry were prepared.
Figure 3 illustrates the scheme for the geometry of the used samples. Notches on both sides of the specimen were made with a Jet JMD-X1 milling machine, which allowed only one layer to be loaded during the test. Therefore, during the compression of the testing machine (traverse speed 1.3 mm/min), interlaminar shear occurred (orange line). All mechanical experiments were conducted with the Zwick/Roell Z020 (Zwick GmbH & Co., Ulm, Germany) universal testing machine at room temperature.
The surface modification of carbon fibers by thermal oxidation was chosen as the method for increasing the interphase interaction between the fibers and the polymer. Carbon fibers were heated and kept in an ambient environment at temperatures of 300, 400, and 500 °C for 30 min in a SNOL muffle furnace (SNOL Ltd., Velikie Luki, Russia). During this article, such fibers will be marked as TO300, TO400 and TO500, respectively. Heated and initials fibers were studied with the AIST-NT Smart SPM atomic force microscope (AIST-NT Inc., Novato, CA, USA). X-ray photoelectron spectroscopy with PHI5500VersaProbeII (Physical Electronics Inc., Chanhassen, MN, USA) was conducted for investigating the types of chemical bonds occurring on the surface of the fibers after modification.
The inner structure of the composites was studied by means of scanning electron microscopy (SEM) with VEGA 3 TESCAN (SEM photos of cracks samples after flexural stress tests) and TESCAN VEGA COMPACT microscopes (SEM photos of etched samples). To obtain SEM photos of the crack samples after the flexural stress tests, the samples were metalized by the magnetron sputtering of a 10 nm thick platinum layer at an amperage of 30 mA.
The thermophysical properties of the obtained composites were identified by dynamic mechanical analysis (DMA). The experiment was conducted using TA Instruments Q800 (TA Instruments Inc., New Castle, DE, USA). The experiment was conducted in the range of temperatures from 25 °C to 220 °C with a heating rate of 2 °C/min; a deformation of 0.1% with a frequency of 1 Hz was applied. The heat deflection temperatures of composites with different reinforcement levels were determined with CEAST HDT 3 VICAT (CEAST S.p.A., Pianezza, Italy). HDT experiments were performed in a silicone bath with initial load of 1.8 MPa and a heating rate of 120 °C/h. The thermal conductivity of the composites was studied in the temperature range from 298 to 498 K in accordance with ASTM E1461-13(2022) (Standard Test Method for Thermal Diffusivity by the Flash Method via Netzsch LFA 447 Netzsch GmbH, Selb, Germany). The study was carried out using square-shape specimens with a thickness of 1.5 mm and a length of each side of 8 mm. Samples were studied in two directions: parallel to the planes of composites and transverse to them. The principle scheme of the experiment is illustrated in
The density of the obtained samples was measured in water by the hydrostatic weighing method using an analytical balance of GR-202 (A&D Company Ltd., Tokyo, Japan) and the density determination was set at AD-1653. TA Instrument Q800 was used to estimate the thermal expansion coefficient.
3. Results and Discussion
Figure 5 illustrates the structure of the obtained composite material with different fiber content. It is shown that the fiber-to-polymer weight ratio has a strong influence on the internal structure of the composite material. Thus, carbon fibers in a composite with a fiber content of 50 wt. % are fully arranged with the matrix polymer. A similar finding can be seen in
Figure 5b, where the 60/40 composite is presented. In both
Figure 5a,b polymer interlayers are visible, which is not peculiar for a composite with a fiber content of 70 wt. % (
Figure 5c). Thus, it can be stated that fiber content strongly influences the structure of composite material.
To identify the best composition of composite material from a mechanical point of view, mechanical tests were conducted. It was found that the composite with a fiber content of 50 wt. % performed the best, reaching 602 ± 23 MPa of flexural strength. The results of the three-point bend test can be seen in
Analyzing the typical stress–strain curve highlights a regularity of special interest. Firstly, the diagram is linear until it reaches a stress of about 400–450 MPa, which means that the material is elastic-deformed and no residual stresses have occurred, despite the thermoplastic nature of the matrix of the composite. Secondly, the E-modulus of the sample rises with rising fiber content. Such a tendency is explained by the higher E-modulus of fibers compared with the PES matrix. The higher content of fibers leads to a more rigid structure of the composite. Despite the highest E-modulus, the sample with the fiber content of 70 wt. % had the lowest flexural strength, which was about 482 ± 28 MPa. The insufficient quantity of the matrix in such a composite explains the observed behavior. Since the matrix in composite materials distributes appearing loads through reinforced fibers, a lack of polymers causes the incomplete relaxation of appearing loads, which leads to the early destruction of the composite material. From this perspective, a composite with a fiber content of 50 wt. % is optimal. When it comes to the fiber content at 40 wt. %, carbon fiber is lacking and the distribution of loads become insufficient again. The results of the flexural strength tests of the composites reinforced with the initial fibers are shown in
In several research studies, interlaminar shear stress has been used as an effective method of the assessment of interfacial interaction in polymer composite materials [
66]. The test showed the same regularities that were found after the bending tests. The results of interlaminar shear test are shown in
Samples with 50 wt. % fiber content were optimal, reaching a shear strength of 20 MPa. A downward trend in shear strength with an increase in fiber content was observed, proving the aforementioned explanation of the existing tendencies. Accordingly, it was shown that a lesser quantity of polymer matrix could not provide sufficient adhesion in the composite materials.
Mechanical tests showed that the optimal fiber content was 50 wt. %, so it was decided to continue the experiments with only this amount of fiber content. To investigate the influence of the surface modification of carbon fibers by thermal oxidation on the adhesion and mechanical properties, a new iteration of mechanical tests for composites reinforced with modified carbon fibers was conducted.
Figure 7 shows the typical stress–strain curves of the composites reinforced with modified fibers, compared with the composites reinforced with the initial CF (fiber content 50 wt. %).
Apart from flexural strength, which reached about 902, 932, and 962 MPa for the composites reinforced with TO300, TO400, TO500 fibers, respectively, the E-modulus raised significantly and was approximately 60 GPa, compared with the initial 50 GPa. Moreover, differences in the mechanisms of destruction and crack spread could be noted. The stress–strain curve for the composite reinforced with initial fibers contained a lot of sharp drops, indicating a crack break in the layers of the composite. Such behaviors of destruction occur when adhesion between the matrix and the reinforcement is insufficient, or loads are not distributed evenly through the fibers. The stress–strain curves for composites reinforced with modified fibers were straight, showing that the cracks opened instantaneously. Tension increases are distributed until a critical amount of energy opens a crack and destroys a sample.
Interlaminar shear tests showed that the surface modification of carbon fibers resulted in a better interfacial interaction between the matrix and the reinforcement. The results of the experiment are shown in
Interlaminar shear strength raised remarkably, reaching about 40 MPa for composites reinforced with modified fibers, which is almost two times higher than the shear strength of the composites with the initial CF.
For the clarification of the mechanism of improvement for the adhesion between the phases of the composite material, X-ray photoelectron spectroscopy and atomic force microscopy of the carbon fibers was conducted.
The analysis of AFM allowed us to investigate the differences in the morphology of carbon fibers after surface modification. The AFM results are presented in
Figure 9. The photo of the initial filament represents the coated surface of the fibers with shallow furrows between the fibrils. After thermal oxidation by heating to 300 °C, coagulation and a change in the structure and morphology of the polymer coating of the carbon fiber occurred, which resulted in the appearance of uneven hills and lowlands on the surface of the filament. The surface modification at 400 °C and 500 °C changed the morphology of the surface of fibers dramatically and seemed to completely remove the coating from the surface of the fibers, exposing the clear surface of the filaments with deep furrows, compared with the initial fibers. Moreover, after oxidation at 500 °C, the furrows became deeper, which can be explained by the oxidation and evaporation of amorphous carbon, which is located between the fibrils.
As it has previously been reported [
63], the surface modification of carbon fibers by thermal oxidation can significantly change the chemical composition of the surfaces of CFs. Here, we show that atomic concentrations of carbon, oxygen, nitrogen, and some other less-comprised elements on the surfaces of CFs changed dramatically depending on the temperature of thermal oxidation. As almost all coatings are made of polymers which contain oxygen (in order to have better adhesion with epoxy resin), the atomic concentration of oxygen can be considered as an indicator of the presence of a sizing agent. After thermal oxidation at 300 °C, the amount of oxygen remained the same; consequently, the coating was not removed after this treatment. Oxidation at the temperature of 500 °C removed the coating completely as the concentration of oxygen dropped. Fluctuations in nitrogen content can be explained by the oxidation of coating after 300 °C treatment, and the further oxidation of amorphous carbon at 500 °C with the release of residual nitrogen.
Surface modification also changes the composition of chemical bonds on the surface of the fibers and controls the adhesion between the reinforcement and the matrix polymer. Compared with the functional groups on the surfaces of the initial fibers, which were CHx, C-O and -COO-, the quantity of the forementioned groups reduced after thermal oxidation at 300 °C. Reduction was interpreted as the oxidation and evaporation of the coating of the CFs. After oxidation at 500 °C, new functional groups occurred such as C=O, -COOH, C-OH, and others, which could be a result of the total decomposition of the coating on the surface.
Consequently, it can be concluded that surface modification improves the interfacial interaction between carbon fibers and PES by the development of surface morphology and the increase in the quantity of functional groups on the surfaces of the fibers by the decomposition of coating [
However, the results of tensile strength tests showed that the strength of the composite materials was invariant to the surface modification of the carbon fibers. The results of experiment are shown in
It was shown that the tensile strength of the composites with different fiber content and reinforced with different modified fibers were approximately the same, reaching about 700 MPa. To understand the reasons for the observed phenomenon, mechanical tests of carbon fibers were conducted. The results of the carbon fiber tensile strength tests can be viewed in
The mechanical tests showed that the tensile strength of the fibers reduced from 1063 MPa to 900 MPa after thermal oxidation. The oxidation of the amorphous carbon of the CFs decreased the mechanical properties of the fibers and, consequently, the properties of the composites reinforced with them. In this case, the reduction in the tensile strength of the carbon fibers outweighed the improvement in the adhesion between the matrix and the reinforcement, which resulted in a drop in the properties of the composite material.
To investigate the internal structure of the composite materials, scanning electron microscopy was conducted. It was noted that increased adhesion between the matrix and the fibers changed the structure of composite. The results of the SEM are shown in
The SEM images show that the composites reinforced with the initial CFs had an empty space between the polymer matrix and the reinforcement. This phenomenon, which was a result of bad interfacial interactions between the PES and the initial fibers, explains the insufficient mechanical properties of the obtained composites. Empty spaces between the phases of the material serve as stress concentrators, which results in the relatively fast destruction of the material. After surface modification at 300 °C, empty spaces are less notable and reinforcing the composite with TO500 fibers allowed us to fully get rid of the aforementioned stress concentrators. Thus, the SEM study proved the earlier expressed explanations of the mechanisms and the behavior of the composite material.
Thermophysical properties are another important group of properties for any constructive material. HDT analysis was conducted to understand the thermal limits of use of the composite materials. The results of the study are represented at
After the study, the following results were obtained. For the composites reinforced with the initial CFs, heat deflection temperature raised steadily from the composite with the fiber content of 50 wt. %, at ~190 °C, to the composite with the CF content of 70 wt. %, at 207 °C. Such a tendency can be explained by taking into consideration the thermal stability of carbon fibers in a given thermal span. Since the composites with 70 wt. % contained more CF, the reinforcement allowed the composites to be more stable and rigid at higher temperatures.
Moreover, the surface modification of the carbon fibers resulted in an increase in thermal stability. Thus, the heat deflection temperature of the composites reinforced with modified fibers reached about 211 °C. Notably, there was no difference in HDT with the thermal oxidation temperature of the reinforced material. Such regularity was accounted for by good adhesion between the matrix and the CF. Polymer chains ‘sticking’ to the surface of the fibers decreased their mobility. In addition, as it was shown with the SEM analysis, the internal empty volume of the composite decreased when the material was reinforced with modified fibers. These two factors resulted in the higher thermal stability of the composite materials.
DMA was conducted for a more detailed investigation of the thermal properties of the composite materials.
Figure 12 represents the results of the analysis.
It has been shown that, generally, all determined thermophysical patterns of obtained composites were the same as during the HDT tests. Thus, the tan δ (loss modulus to storage modulus ratio) was at the maximum point at the temperatures of 195 °C, 208 °C and 213 °C for the composites containing 50, 60, and 70 wt. % initial CF, respectively. Moreover, it has been shown that tan δ was in inverse ratio with fiber content: with the increase in fiber content the maximum value of tan δ lowered. Such a phenomenon can be explained by the lesser thermal stability of polymer matrices with carbon fibers, which results in the loss of the elastic properties of the composites.
The surface modification of carbon fiber influenced the thermal stability of the composites, as well as their viscosity. It was shown that the maximum temperature of thermal stability increased when the peak value of tanδ was significantly lowered, which illustrates the elastic behavior of the composite material during the softening process. Thus, the tan δ of the composites reinforced with initial CF peaked at 0.75, while the maximum value of tan δ for the composites reinforced with modified fibers reached ~0.5. Some studies conducted on polymer-based composite materials have shown that the maximum value of tan δ is influenced by the interfacial interaction between matrix and reinforcement [
67]. Therefore, the decrease in tan δ showed better interfacial interaction between the modified fibers and PES. Better adhesion between the phases of the composites limits the thermal mobility of the polymer chains, increasing the viscosity of the polymer matrix and consequently lowering loss modulus.
Thermal conductivity is one of the most important thermophysical properties of carbon fiber-reinforced composites. It determines in which conditions composites can be used. Thermal conductivity was investigated with the laser flash technique (LFA), which is considered as an effective method of studying thermal conductivity. Since the obtained composite materials have an anisotropic structure, thermal conductivity was studied in two directions: along the layers of the carbon fibers and perpendicular to them. The results of the experiment are shown in
It was shown that thermal conductivity is strongly influenced by the fiber content and direction of the carbon fibers. Thus, the thermal conductivity (studied perpendicular to the layers of CF at room temperature) of the samples with fiber contents of 70 wt. %, 60 wt. %, and 50 wt. % reached the values of 0.68, 0.6, and 0.53 W/m·K, respectively. The analysis of the results along the layers of reinforced material showed a much higher thermal conductivity of composites. Hence, the coefficients of the thermal conductivity of the composites studied in the layer direction were 4.22, 3.16, and 2.71 W/m·K for the samples with fiber contents of 70, 60, and 50 wt. %, respectively. It is well-known that carbon fibers intensively conduct heat [
68], so increasing the amount of carbon fibers explains the corresponding rise in thermal conductivity. Moreover, when the investigated value was studied in the direction perpendicular to the layers of reinforced material, heat flowed through the interlayers of the polymer matrix that did not have properly impregnated carbon fibers (
Figure 14). Such interlayers had significantly lower coefficients of thermal conductivity, explaining the observed phenomena. When the direction of heat flow distribution coincides with the direction of the layout, no obstacles in the way of the heat flow are present, which results in a dramatically better release of the potential thermal conductivity of the carbon fibers in the obtained composites. Therefore, considering that the main thermal conductors are carbon fibers, interphase interactions between fibers and polymer matrices may not notably influence the thermal conductivity of the composites. Consequently, such influence was not studied in this research. Considering the thermal conductivity of the carbon fibers as 10 W/(m·K), the release of the initial properties of the reinforced material was about 55–60% for the obtained composites.
Another important feature of any constructive composite material is the coefficient of thermal expansion. The low coefficient of thermal expansion allows the material to stay stable throughout heating. The coefficient of thermal expansion was indirectly investigated by means of TA Instruments Q800. As in the study of thermal conductivity, the thermal expansion of the composite material was studied in two directions. The results of the experiment can be shown in
It is noteworthy that CTE expansion is strongly influenced by fiber content. The difference in the thermal expansion coefficient of carbon fibers and the polymer matrix allows us to manage its value by changing the fiber content of the composite material. Thus, the coefficient of the linear expansion of the composites reinforced with 70 wt. % fibers reached the value of 2.7 × 10
−5 mm/(m × °C). Moreover, in the direction parallel to the axis of reinforcement, CTE became negative (
Figure 15). Such phenomena can be explained by the “negative CTE” of carbon fibers when they shrink along their axis with the rise in temperature [
69]. Thus, the coefficient of thermal expansion for the 50/50 composite was about −0.69 × 10
−5 mm/(m × °C).
According to the results of the study of CTE, it is potentially possible to develop and obtain composite material of a particular fiber content in which CTE is close to zero in the investigated range of temperatures.
During the study, the mechanical and thermophysical properties of carbon fiber-reinforced composite materials based on polyethersulfone were investigated. Moreover, the influence of the surface modification of carbon fibers via thermal oxidation on the mechanical and thermophysical properties of the composites was investigated.
X-ray spectroscopy of the surfaces of the carbon fibers showed that the surface modification of the carbon fibers resulted in changes in the chemical composition of the surfaces of the fibers. An increased quantity of C atoms on the surface of the fibers was considered as an indicator of the destruction of the coupling agent on the surface. Moreover, an extended quantity of types of chemical bonds could be referred to as the decomposition of the coupling agent as well.
Atomic force microscopy allowed us to investigate changes in the morphology of the surface. It was shown that several changes in the structure of the surface occurred. Thus, after thermal oxidation at 400 °C, some irregularities on the surface of the fibers appeared, and were interpreted as the coagulation and decomposition of the coupling agent. Therefore, considering the results of the X-ray spectroscopy and AFM, it is concluded that the surface modification of carbon fibers via thermal oxidation could change the chemical composition and morphology on the surface of the CFs.
Because of the changes occurring on the surfaces of the carbon fibers during surface modification, the thermal oxidation of CF can dramatically change the properties of the obtained composite materials. Thus, the thermal oxidation of CF can dramatically change the properties of the obtained composite materials. It has been shown that composites reinforced with modified (TO500) fibers have a flexural strength of about 960 MPa and an E-modulus of 60 GPa. For composites reinforced with initial fibers (fiber content 50 wt. %), the same values were ~600 MPa and ~50 GPa, respectively. The interlaminar shear strength test was interpreted as the measure of adhesion between the polymer and the reinforcement. Surface modification increased the shear strength of the composites by 50%, reaching the values of 40 MPa. However, thermal oxidation lowered the mechanical properties of the carbon fibers, which consequently resulted in a low tensile strength of the composite materials, at about 700 MPa.
Regarding the thermophysical properties, the heat deflection temperature of the composites reinforced with modified fibers was ~211 °C. Increased thermal stability was explained by sufficient interfacial interaction between the polymer chains and the surfaces of the CFs, which led to the lower mobility of the chains and consequently to better thermal stability. Moreover, DMA showed that the behavior of heat softening changed depending on the interfacial interaction in the composites. The composites reinforced with modified fibers showed lower values of tan δ, which can be interpreted as further evidence of improved adhesion between PES and CF.
The thermal conductivity of the composites with different fiber contents of reinforced initial fibers was studied. As the obtained composite materials had an anisotropic structure, thermal conductivity was strongly influenced by the investigated direction. Thus, thermal conductivity coefficients were studied in the directions parallel to the layers of reinforcement and perpendicular to them. It was shown that, in both directions, the best thermal conductors were the 70/30 samples. The observed phenomena is a consequence of the higher thermal conductivity of carbon fibers compared with the polymer matrix, leading to the rise in the thermal conductivity of the composite with the increasing quantity of carbon fibers. Moreover, the obtained composites conducted heat flow more efficiently when co-axial to the carbon fiber direction. The suggested explanation for such behavior consists of the hypothesis that heat flow is distributed continuously by CF without facing the less conductive areas of the polymer.
The coefficient of thermal expansion also depended on the fiber content. Since carbon fibers have so-called negative CTE parallel to their axis direction, the composite materials shrank when co-axial to the reinforcement direction. This factor determines the possibility of the development of materials based on the described composites with geometry, invariant to heat.