CRP moulding is claimed to be as strong but lighter than an aluminium part
A high-performance moulding compound from Hexcel has been used to produce a carbon fibre reinforced plastic (CFRP) transmission crossmember using a zero waste process said to be ideal for high volume manufacture.
The automotive part is comparable with aluminium versions in terms of its performance and price but could be 30–35% lighter, the developers said.
The transmission crossmember was developed by Hexcel and the Institute of Polymer Product Engineering (IPPE) at the University of Linz, Engel and Alpex.
Hexcel's director of sales and marketing for Automotive, Achim Fischereder, said: "These parts connect either side of a vehicle's chassis together and support its transmission, and must be stiff, strong, and resistant to fatigue. As they are exposed to the road, they must also be resistant to stone chipping and corrosion caused by water and salts."
To meet these requirements, the partners used HexMC-i 2000, which is claimed to be the best-performing moulding compound available, to produce the part. The material has been designed specifically to bridge the price/performance gap between sheet moulding compounds (SMCs) and prepregs and is stiffer than steel at approximately a fifth of the density. Its mechanical performance is highly consistent.
HexMC-i 2000 comprises randomly orientated rectangular chips of unidirectional carbon fibre-reinforced prepreg impregnated with M77 snap-curing epoxy resin to form a 2000gsm sheet material. The moulding compound can cure in as little as two minutes to produce lightweight, strong and stiff parts.
To produce the transmission crossmember, preforms are laid up in moulds fabricated by Alpex and compression moulded using a v-duo press that has been tailored for the application from Engel. Ribs, aluminium inserts and other functions can be moulded into the part using the single stage process, reducing component count in comparison with metal versions of the part and keeping costs low.
Crucially, any offcuts from the preforms can be interleaved between the plies of material to provide additional reinforcement in key areas, meaning the process generates no waste.
Another option being explored by the partners is to transform these offcuts into carbon fibre mat prepreg using techniques developed by Carbon Conversions (CCI), a company in which Hexcel acquired a stake in late 2016.
Thanks to advanced finite element method (FEM) simulation techniques developed by IPPE, the design of the part is highly optimised, and it demonstrates the strength and fatigue resistance demanded by the application.
Fischereder added: "Using the predictable, zero waste process we have developed, we have shown that we can match the performance and price of metallic structural components while reducing weight significantly."
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