Kevlar

From Boat Design Wiki

Kevlar is a DuPont trade name for a synthetic aramid fibre. A similar fibre is manufactured by Teijin under the name Twaron.

The para-aramid structure results in a fibre that has excellent tensile strength, between 3 to 3.5 gigapascals at tensile failure. It is very stiff in tension, generally with a tensile modulus of roughly 70 to 120 GPa depending on grade and fabrication process. This makes it one of the most structurally efficient materials available for a purely tensile application. Kevlar has good abrasion resistance and is extremely difficult to cut and work. It is substantially weaker in compression than in tension, and care must be taken when designing hulls and rigs with Kevlar to ensure that this property is accounted for. The material degrades under ultraviolet light and must be protected from direct sun exposure.

The common Kevlar fibre or fabric is generally used as a reinforcement within a flexible component such as a drive belt.

A more refined grade known as Kevlar 29 is seen in cables, body armour and industrial applications.

Kevlar 49, the strongest grade in common use, is most commonly seen in a thermoset polymer matrix forming the shell of an aircraft or boat.

A relatively new form, Kevlar 149, increases the tensile strength to 3.45 GPa (compared to 3.0 in Kevlar 49) and the tensile modulus to 179 GPa (from ~112 in Kevlar 49). It is attracting the attention of the aerospace industry but is not commonly seen at the consumer level yet.

A search in the Aramid category at MatWeb will provide additional technical data on Kevlar in its various forms.