High-volume, zero-waste process enabled by Hexcel moulding compound
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 ideal for high-volume manufacture. The automotive part is comparable with aluminum versions in terms of its performance and price, but could be 30–35% lighter.
The transmission crossmember has been developed by Hexcel and the Institute of Polymer Product Engineering (IPPE) at the University of Linz, Engel and Alpex. These parts connect either side of a vehicle’s chassis together and support its transmission and therefore must be stiff, strong, and resistant to fatigue.
To meet these requirements, the partners selected HexMC-i 2000, which is the best-performing moulding compound currently on the market, to produce the part. HexMC-i 2000 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. Further, its mechanical performance is highly consistent.
HexMC-i 2000 comprises randomly orientated rectangular chips of unidirectional carbon fibre-reinforced prepreg impregnated with Hexcel’s 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 of HexMC-i 2000 are laid up in molds fabricated by Alpex and compression-moulded using a v-duo press that has been tailored for the application from Engel. Ribs, aluminum 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 that the process generates no waste whatsoever.