In 1963, this material was invented by Stephanie Kwolek, from fibres of nylon polymers. The density of this material is high and low in weight. In comparison to steel, this material is five times stronger than steel, which can become an alternative to steel. The fibres of this material are used in bicycle tyres, bulletproof vests, walking boots, fibres for composite materials for aircraft panels, boat hulls and golf club shafts. These fibres can also be used in high-density fabric structures.
The tensile strength of this material is around 3600mPA, with inter-spun fibres. In 1971, this material started being in use in racing tyres in replacement to steel. This material has started being used in armoured walls, turbines, smartphones, and expansion joints, recently. There are three different types of Kevlar material: Kevlar, Kevlar 29, and Kevlar 49.
Kevlar 29 is mainly used in armoured military vehicles, and Kevlar 49 is used in aerospace and marine applications. In the building construction industry, this material was firstly used in 1976 in the Montreal Olympics. The roof of the stadium was made with this material, which took 10 years to complete. Later this material was used in Miami, in order to construct hurricane-proof structures.
The chemical properties of this material consist of monomers of paraphenylenediamine and terephthaloyl chloride. When the chemical reaction takes place terephthaloyl chloride becomes the byproduct. During synthesis during this process, DuPont replaced the hexamethylphosphoramide with N-methyl pyrrolidone and calcium chloride, due to safety reasons.
To sprinnet and spin the crystalline form of Kevlar, highly concentrated sulphuric acid was added. This is one of the most expensive steps in the entire process of Kevlar production.
This material has high tensile strength, which makes it 8 times stronger than steel, but its compressive strength is extremely low. Due to this kevlar isn’t appropriate for replacing steel in buildings and bridges. The strength of this material, especially in fabric form, is quite commendable, but the fibres absorb moisture when exposed to the environment. This material reacts badly to UV radiation if it’s used in the exterior. But a UV stabilizer can be applied for exterior usage.
Fibre Reinforced Concrete with kevlar fibres is a new material, known as KFRC. The composition consists of Kevlar fiber with cement and sand. The fibre in this composition acts as a crack restrictor. The fibres stop the cracks from enlarging and keeps the structure bound. If the fibres are closely placed, the surface of the concrete can be crack free.
Many architects have experimented and proposed various architectural projects considering Kevlar as one of the most important construction materials. The first project with Kevlar as a construction material was constructed in Canada in Montreal by architect Roger Taillibert. Along with him was engineer Luc Lainey who also worked on this project in 1976. He took almost a decade to complete the project. He designed the stadium that resembled an Australian expo in Japan. This was the sixth tallest building in Montreal.
The roof of this building was a retractable structure connected by cables. In 1985 the roof was added to the project, which was made of kevlar—orange in colour. As the monsoons started, the roof started ripping off causing leakages. Later the roof was repaired and came underuse again.
But in 1992 a windstorm hit the city and the roof was ripped off. After that in 1998, a new roof was installed which was opaque and non-retractable. Every time the roof rips off when it snows or rains heavily. It almost rips 50 to 60 times in a year, leading to repairing it frequently. This roof is anchored to the concrete roof, with 26 suspension points and 17 cable points. These cables are connected to the tower bringing the roof to the height of 168 m. To protect the roof from UV radiation and weather conditions, a PVC membrane that is ventilated on both sides is clamped with Kevlar.
Architect Peter Testa designed a prototype of a skyscraper, which has fiberglass and kevlar as a construction material. When this carbon fibre is mixed with kevlar, it becomes five times stronger than steel and is becoming one of the useful materials. The carbon fibres used in the prototype are 1 inch thick and 650 feet long.
To achieve the strength of the material, it is either cross-hatched or helicoidal pattern. The floor slabs are constructed in glass. The entire prototype is constructed with different types of composite materials, which adds strength to the prototype. In this prototype, a lot of research is still going on, but the major challenge here is the cost of the project. Carbon fibre is an expensive material, increases the cost of the project.
