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Development of Thermoplastic Composites for Aerospace Applications
The major limitations of thermoset polymers are their inability to be re-melted or recycled, shorter shelf-life, higher storage costs, and longer curing times thereby opening up opportunities for using thermoplastic based composites. Thermoplastic composites (TPCs) offer unlimited shelf-life of raw materials, rapid production cycle, and recyclability of scrap. They are much tougher than comparable thermosets, offer substantial reductions in flammability, smoke and toxicity (FST) performance and are relatively insensitive to chemical attack. High performance thermoplastics that are applied in aerospace structural composites are poly ether ether ketone (PEEK), poly aryl ether ketone (PAEK), polyphenylene sulfide (PPS), polyetherimide (PEI) and polyamides (PA).
Thermoplastic composites can be processed using autoclave, hot-press and in-situ consolidation. Autoclave molding though relatively expensive is still considered as a potential technique especially when complex curved integrated structures are to be manufactured. Hot-press compression molding is found to be more useful where medium to small components like simple curved panels, spars, ribs, stringers, clips, cleats, and brackets are to be produced in large volumes.
At CSIR-NAL both hot-press and autoclave facilities are available. The processing of PPS and PEEK based thermoplastic composites is demonstrated using both hot-press and prepreg-autoclave molding technique. Parts like wing nose skins, spars and skin-stringer panels are realised using PPS/glass and PPS/carbon composites in an autoclave. However, the hot-press molding has also been used for optimization of process parameters by processing of flat test laminates and manufacture flat panels for mechanical test data generation. Further, processing of small components like clips has also been demonstrated. This hot-press facility will further be expanded in terms of platen size and automation to manufacture the parts like aileron skin and ribs and wing spars.
Process Cycle for PPS composites Raw material- Semipreg
Hot-Press Molded L-Angle Clip Autoclave Molded Wing Spar
Facilities where this techniques is used
Autoclave and Hotpress
Major mile stone/results of this technique
- Capability to process wing nose, spars and skin-stringer panels using autoclave molding.
- Capability to thermoform clip like parts using hot-press compression molding technique.
