Today's KNOWLEDGE Share: Composite Essentials

 Today's KNOWLEDGE Share:

Composite Essentials

Let's learn more about the different weave patterns in woven fabrics!

Woven fabrics are woven yarns, rovings, or tows in mat form in a single layer, in which the amount of fiber in different directions is controlled by the weave pattern. The most common are Plain, Twill and Harness Satin! 

In a plain-weave pattern, fibers in 0° and 90° directions are equally distributed. A plain weave carbon fiber sheet looks symmetrical with a small checkerboard style appearance. In this weave the tows are woven in an over/under pattern. 

In a twill weave, the tow strand passes over a set number of tows and then under the same number of tows. The over/under pattern creates a diagonal arrowhead look, known as a “twill line”. 2×2 Twill is likely the most recognizable carbon fiber weave in the industry. It is used in many cosmetic and decorative applications, but also has great functionality, it has both moderate formability and moderate stability. As the 2×2 name implies, each tow will pass over 2 tows then under two tows.

The number in the Harness Satin names indicates the total number of tows passed over then under. For 4HS, it will pass over 3 tows then under 1. For 5HS, it will pass over 4 then under 1, and 8HS will pass over 7 and under 1. Common harness satin weaves are 4 harness satin (4HS), 5­ harness satin (5HS) and 8 harness satin (8HS). As you increase the number of the satin weave, formability will increase and fabric stability will decrease. 

In this picture you can see how the weaving process can yield many different patterns! 

Bibliographical Reference:

Composite Manufacturing - Materials, Product and Process Engineering - Page 54

Elevated Materials Article "Carbon Fiber Weaves: What they are and why to use them"

Source:managingcomposites/thenativelab

Today's KNOWLEDGE Share:FTIR

 Today's KNOWLEDGE Share:

Fourier transform infrared spectroscopy (FTIR) is a fundamental tool for the qualitative compositional analysis of polymeric materials. It allows the user to identify the material being tested. In order to properly interpret the results of FTIR, the key considerations regarding spectral band formation must be understood.

 

 FTIR bombards with infrared energy, and certain frequencies are absorbed by the sample and others transmitted. The frequencies at which the material absorbs infrared energy correspond to molecular vibrations that are produced within the sample. The infrared spectrum representing a material consists of absorption bands associated with discrete functional groups, the building blocks that make up the molecule. The frequency at which a functional group absorbs is based on a number of factors:

 

Atomic weight of the bonded species: Frequency decreases (lower cm-1) with increasing atomic weight.

 

Bond energy: Frequency increases (higher cm-1) with increasing bond energy.

 

Surrounding molecular structure: The adjacent molecular structure changes the vibrations of the subject bond, for example conjugation lowers the frequency (lower cm-1).

  

An important implication of this is the absorption bands associated with halogenated polymers, particularly fluoropolymers. The C-X stretching and bending frequencies occur at lower frequencies (lower cm-1) in C-I < C-Br < C-Cl < C-F < C-H. This is primarily due to the effects of the molecular mass bond energies. Because of this shift, the presence of a halide is often difficult to confirm by means of the infrared spectroscopy.

 

I have illustrated the spectral band shift between analogous C-H bond and C-F bands in polyethylene and polytetrafluroethylene, respectively, in the color-coded graphic below.

Source:Jeffrey A. Jansen

Today's KNOWLEDGE Share:carbon fibers possess such a high modulus in the direction of the fibe

Why does carbon fibers possess such a high modulus in the direction of the fiber?

As many questions related to materials engineering, to answer that we have to understand the unit cell structure of the material, in this case, graphite.

The crystal structure of graphite, consists of sp2 hybridized carbon atoms arranged two-dimensionally in a honeycomb structure in the x-y plane. The layers, termed graphene layers, are stacked parallel to each other in a 3D structure. The most common stacking sequence of the layer planes is the hexagonal form with an ABABAB packing sequence. This way, some atoms (α) have neighbors directly above and below in adjacent planes, while others (β) don’t. The bonding between the layers is van der Waals bonding, so the carbon layers can easily slide with respect to one another.

Due to the difference between the in-plane and out-of-plane bonding, graphite has a high modulus of elasticity parallel to the plane and a low modulus perpendicular to the plane. Thus, graphite is highly anisotropic. The high modulus of a carbon fiber stems from the fact that the carbon layers, though not necessarily flat, tend to be parallel to the fiber axis.

Source:#managingcomposites

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#carbonfiber #composite #cellstructure #graphite #carbonatom #elasticity

Today's KNOWLEDGE Share-FIRST APPLICATION OF CARBON FIBER

Today's KNOWLEDGE Share:

FIRST APPLICATION OF CARBON FIBERS
Carbon fibers are older than you imagine! The first carbon fibers date back to 1860! In 1879, a certain guy named Thomas Edison chose carbon fibers to manufacture light bulb filaments. At that time, they were not petroleum-based. Instead, they were produced through the pyrolysis of cotton or bamboo filaments. These filaments were ''baked'' at high temperatures to cause carbonization to take place.

But why were they chosen? The answer is pretty straightforward and has nothing to do with high strength! At the time, Edison noticed that their high heat tolerance made them ideal electrical conductors. However, soon later tungsten took over as the light bulb filament of choice in the early 1900s, and carbon fiber became obsolete for the next 50 years or so.

During the 1960s, a Japanese researcher named Akio Shindo, manage to manufacture carbon fibers using PAN as a precursor. This way, his team was able to achieve a filament that had ~55% carbon, using a much more cost-effective production method. This new technology allowed for the resurgence of carbon fibers, but this time, they were here to stay!

Source:composites Industry/managingcomposites

Tata-owned Air India places giant order for 470 planes with Airbus and Boeing

 The order comprises 40 Airbus A350s, 20 Boeing 787s and 10 Boeing 777-9s widebody aircraft, as well as 210 Airbus A320/321 Neos and 190 Boeing 737 MAX single-aisle aircraft. The A350 aircraft will be powered by Rolls-Royce engines, and the B777/787s by engines from GE Aerospace. All single-aisle aircraft will be powered by engines from CFM International.

Commenting on the occasion, Tata Sons and Air India Chairman, Mr N Chandrasekaran, said: “Air India is on a large transformation journey across safety, customer service, technology, engineering, network and human resources. Modern, efficient fleet is a fundamental component of this transformation. This order is an important step in realising Air India’s ambition, articulated in its Vihaan.AI transformation program, to offer a world class proposition serving global travellers with an Indian heart. These new aircraft will modernise the Airline’s fleet and onboard product, and dramatically expand its global network. The growth enabled by this order will also provide unparalleled career opportunities for Indian aviation professionals and catalyse accelerated development of the Indian aviation ecosystem.”

The first of the new aircraft will enter service in late-2023, with the bulk to arrive from mid-2025 onwards. In the interim, Air India has already started taking delivery of 11 leased B777 and 25 A320 aircraft to accelerate its fleet and network expansion.

The acquisition of new aircraft, which will come with an entirely new cabin interior, complements Air India’s previously announced plan to refit its existing widebody B787 and B777 aircraft with new seats and inflight entertainment systems. The first of these refitted aircraft will enter service in mid-2024.

The Air India group currently comprises full-service Air India, as well as two low-cost subsidiaries Air India Express and Air Asia India which are in the process of merging. Its parent, Tata Sons, recently announced its intention to merge Air India with full-service airline Vistara, a joint venture between Tata Sons and Singapore Airlines in which the former holds a 51 % share. In steady state, subject to regulatory approval, the Group would comprise a single full-service airline, Air India, and a single lowcost airline, Air India Express.

Source:Airindia/jeccomposites

Today's KNOWLEDGE Share:Dry-jet wet spinning process to produce aramid fibers

 Today's KNOWLEDGE Share:

Dry-jet wet spinning process to produce aramid fibers

Aramid fiber is a generic term for a class of synthetic organic fibers called aromatic polyamide fibers. The U.S. Federal Trade Commission gives a good definition of an aramid fiber as “a manufactured fiber in which the fiber-forming substance is a long-chain synthetic polyamide in which at least 85% of the amide linkages are attached directly to two aromatic rings.” Well-known commercial names of aramid fibers include Kevlar and Nomex (DuPont) and Twaron (Teijin Aramid).

The basic chemical structure of aramid fibers consists of oriented para-substituted aromatic units, which makes them rigid rod-like polymers. The rigid rod like structure results in a high glass transition temperature and poor solubility, which makes the fabrication of these polymers, by conventional drawing techniques, difficult. Instead, they are spun from liquid crystalline polymer solutions by dry-jet wet spinning.

The dry-jet wet spinning starts with a solution of polycondensation of diamines and diacid halides at low temperatures (near 0 °C) gives the aramid forming polyamides. Low temperatures are used to inhibit any by-product generation and promote linear polyamide formation. The resulting polymer is pulverized, washed, and dried; mixed with concentrated H2SO4; and extruded through a spinneret at about 100 °C. The jets from the orifices pass through about 1 cm of air layer before entering a cold water (0–4 °C) bath. The fiber solidifies in the air gap, and the acid is removed in the coagulation bath.

The spinneret capillary and air gap cause rotation and alignment of the domains, resulting in highly crystalline and oriented as-spun fibers. The air gap also allows the dope to be at a higher temperature than is possible without the air gap. The higher temperature allows a more concentrated spinning solution to be used, and higher spinning rates are possible. Spinning rates of several hundred meters per minute are not unusual. The as-spun aramid fibers are washed in water, wound on a bobbin, and dried. Fiber properties are modified by the use of appropriate solvent additives, by changing the spinning conditions, and by means of some post-spinning heat treatments, if necessary.

Bibliographical Reference:

Composite Materials - Science and Engineering - Page 46

Source:managingcomposites

Visit MY BLOG http://polymerguru.blogspot.com

#aramidfibers #polyamide #kevlar #twaron #nomex #composites #dryjetwetspinning #spinning

Today's Knowledge Share-HYDROGELS

 Today's Knowledge Share:

HYDROGELS:

Hydrogels are one of the hottest topics in bioelectronics.

Conductive hydrogels, in particular, might prove crucial for treating nerve injuries.Hydrogels are networks of polymers that hold a large amount of water - like a jelly.

By inserting polyacrylamide and polyaniline, researchers in China were able to create hydrogels that conduct electricity.

They demonstrated that this new material could treat nerve injuries by forming a conducting biocompatible link between broken nerves.

Peripheral nerve injury – for example, when a peripheral nerve has been completely severed in an accident – can result in chronic pain, neurological disorders, paralysis, and even disability.They are traditionally very difficult to treat.

The new hydrogel could change this.

The team implanted the hydrogel into rats with sciatic nerve injuries. The rats’ nerves recovered their bioelectrical properties – as measured by electromyography one to eight weeks following the operation – and their walking improved.

Irradiating the hydrogel with infrared improves the conductivity from 1.95 nA to 2.3 nA.

Source :https://pubs.acs.org/doi/abs/10.1021/acsnano.0c05197