Co-authors​ :

 Connie QIAN (UNITED KINGDOM), Hao YUAN , Tom HILL , Richard GROVES (UNITED KINGDOM), Adam JOESBURY (UNITED KINGDOM), Lee HARPER  

It is of great industrial interest to develop commercially viable solutions to reclaim and reuse carbon fibre prepreg manufacturing waste (e.g. offcuts) to avoid landfills. One possible approach is to reprocess prepreg waste into chip-based sheet moulding compounds (chip-SMC), which flow under heat and pressure to fill the mould cavity when compression moulded, but most studies on such materials have focused on UD fibre prepregs [1, 2]. A recent research conducted by the authors [3] assessed the feasibility of employing the chip-SMC approach for a woven fibre based prepreg, and it was reported that while the resultant materials had comparable flow abilities with conventional SMCs, the tensile strengths were merely 40% of those for conventional SMCs due to the high levels of heterogeneity caused by the interlacing tows, limiting these materials to non-structural applications. A similar study [4] using an aerospace grade woven prepreg reported that the strengths could be doubled using a slow cooling profile to allow a more uniform temperature distribution during chemical shrinkage, but such approach would be unsuitable for high volume manufacturing.
Compression moulding of continuous-discontinuous fibre composites is an attractive solution for high-volume manufacturing of structural composites through the combination of the great formability of discontinuous fibre composites and the superior mechanical properties of continuous fibre composites. Therefore, this paper seeks new an application route for woven fibre based chip-SMCs by co-moulding the chip-SMC with the original continuous fibre prepreg to form a hybrid architecture composite. This research contains a series of experimental studies. Firstly, baseline material characterisations are performed using bespoke squeeze flow rig [5] to study the critical deformation mechanisms for continuous fibre prepreg, chip-SMC and hybrid architecture composite. Secondly, parametric studies are performed to optimise the processing conditions (e.g. temperature, compression speed) and material parameters (e.g. staging, prepreg chip sizes) such that manufacturing defects (e.g. unfilled cavity, excessive distortion in continuous fibres) can be minimised. Meso-scale fibre analysis techniques such as micro-sectioning and XCT are adopted to provide qualitative and quantitative assessments of the defects. Finally, a demonstrator geometry with complicated 3D features (Figure 1) is manufactured to assess the practicality of the proposed new manufacturing strategy, and to identify any challenges that need to be resolved in future work.