What are the Advantages and Disadvantages of Kevlar Fiber?

The demand for high performance in engineering products is ever-increasing. Thus, in response to this, we are seeing the emergence of innovative and advanced materials. These materials are birthed by combining different sub-materials for a higher quality than what one material will give. One such is Kevlar.

Kevlar is a member of the Aramid family of synthetic fibers, which was invented by Dupont. Kevlar fiber can be found in roving, veil mats, chopped strands, or woven fabrics, and it is used in a variety of products ranging from protective armor to ropes and cables. It has many advantages, but it also has some disadvantages.

Advantages of Kevlar Fiber

Exceptional strength

The para-aramid fiber known as "Kevlar" has a relative density of 1.44 and a tensile strength of about 3,620 MPa. This makes it strong while remaining lightweight.

Although lighter than steel, it is strong. Kevlar's chemical structure is made up of several repeating inter-chain bonds. Due to the hydrogen bonding in these chains, their tensile strength is 10 times greater than steel's for equal weight.

Zero thermal shrinkage

Kevlar retains its strength and resilience down to cryogenic temperatures (196C), implying that there is no embrittlement at such low temperatures.

It can also withstand temperatures of up to 450C. It becomes a little bit stronger at cold temperatures. The tensile strength diminishes by around 1020% right away at higher temperatures and continues to decline over time.

Excellent heat and flame resistance

After more than 200 days of exposure to heat, such as hot water, Kevlar fiber can remain virtually unchanged. Kevlar is naturally flame resistant, withstanding temperatures of up to 800 degrees Fahrenheit.

Kevlar fibers will not melt, drip, or burn. It can be ignited, but when the source is removed, the burning stops.

Resistant to tearing and stretching

Because of their high resistance to impact damage, aramid fibers are frequently used in areas prone to impact.

Kevlar fiber's completely expanded and well-aligned molecular chains act as a powerful barrier to prevent wounds, scratches, and pricks.

It is resistant to almost all types of chemicals, giving it the properties of high cut resistance.

High-velocity defense

Kevlar fibers are so tightly spun that separation is nearly impossible. When a bullet or other high-velocity projectile strikes Kevlar, the fibers absorb and dissipate the energy.

Disadvantages of Kevlar Fiber

Despite its strength and resilience, Kevlar has some drawbacks that limit its effectiveness.

Absorbing moisture

The quick absorption of moisture by Kevlar fibers makes them more environmentally sensitive than other materials. Although only prolonged exposure to moisture degrades Kevlar, this moisture absorption can render it unsuitable for damp environments.

Minimal compressive strength

Kevlar has a good degree of strength and tensile, but it has a poor tolerance for compression, making it challenging to cut.

Cutting and drilling are difficult

Dry fabric is usually cut with special scissors, and cured laminates can only be pierced with special drill bits.

Ultraviolet light sensitivity

In comparison to polyester, Kevlar loses strength in sunlight about twice as fast due to its rapid absorption of ultraviolet light. This can cause a decrease in fiber properties over time.

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