Net shape spray deposition for compression moulding of discontinuous fibre composites for high performance applications

Abstract

Details are presented of a novel carbon/epoxy spray deposition process for producing high performance, net shape charges for low flow compression moulding. The Bentley–Raycell automated carbon composite charge deposition (BRAC3D) process sprays powdered epoxy and chopped carbon bundles onto three-dimensional (3D) tools, offering a fully automated process with no touch labour. It has been demonstrated that fibre volume fractions of up to 54% are achievable for random discontinuous fibre architectures, with low void content (1·6%). This extends the volume fraction range currently offered by liquid moulding/preforming processes and potentially reduces part scrap rate, since the resin flow direction is through thickness rather than in-plane. Results from an experimental programme are presented, which aims to benchmark the BRAC3D material against commercial advanced moulding compounds. Ultimate tensile strength, tensile modulus and Charpy impact values are reported to be 272 MPa, 44·4 GPa and 128 kJ m^–2 respectively, for the random fibre architecture at a fibre volume fraction of 54%. This equates to a 99% stiffness retention and a 59% strength retention compared to a continuous fibre, quasi-isotropic counterpart. Observed trends for increasing fibre volume fraction and fibre length have been compared against finite element predictions and an analytical inclusion model. Simulations from a parametric cost model indicate that the BRAC3D process is cost effective for production volumes exceeding 1100 ppa for a structural demonstrator component, compared with prepreg and resin transfer moulding.

Keywords

DISCONTINUOUS CARBON FIBRE SPRAY DEPOSITION COMPRESSION MOULDING EPOXY FINITE ELEMENT

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