Composite materials have been in use in aerospace & missiles for a long time especially where high strength to weight ratio, directional properties, corrosion resistance, stealth and ease of manufacturing are pre-requisites. Composites normally use glass or carbon fiber & epoxy resins for bonding. In the Agni-V the third stage was made of composites. Pune based Research & Development Establishment (Engineering) or R&DE(E) has pioneered the application of composites in design, development of structures for army & naval applications such as all composite single span bridges, armour vehicles with integral ceramic composite hull etc. In the process they have developed special manufacturing process like Vacuum Assisted Resin Transfer Moulding (VARTM) and Resin Film Infusion (RFI).
Composite Bridges. Using carbon fibres & epoxy a 5 m long and 4 m wide bridge has been successfully developed which is 30 per cent lighter than Aluminum Bridge, and at similar cost. The bridge weighs 1.2 tons and is designed for MLC 70 load class. Each tread way of the bridge with a deck-I girder configuration is monocoque without joints. VARTM process has been used to manufacture the bridge. This bridge is smart as it can monitor itself through fibre optic sensors embedded in the bridge.
Sonar Domes. The domes made of FRP for the destroyers of the Indian Navy are being developed. The sound waves are attenuated much less while passing through such domes & resulting in better target detection apart from being cost effective.
Ceramic Armour. Most exciting in defence application is the successful development of composite integrated hull section of an armoured vehicle. It consists of ceramic tiles and rubber sandwiched between two fibre reinforced plastic layers. The ceramic tiles provide protection against ballistic/kinetic impact; the FRP provides covering & structural strength while rubber provides cushion for the ceramic tiles. The structure along with the armour is fabricated in one go with no joints using VARTM process. Such armour is 40% lighter than steel providing similar protection with much ease of manufacture.
Nano technology. Nano materials can improve material properties quite dramatically. As such R&DE (E) is working on nano silica filled epoxy resin blends and carbon nano tube in epoxy resins. Influence of addition of nano materials on flow properties is being investigated. Modified resins are being produced for processing glass epoxy composites by RFI technique. The nano filler modified composites have shown promising results.