Characterisation of Random Carbon Fibre Composites From a Directed Fibre Preforming Process: The Effects of Moulding Process and Fibre Type

This paper investigates the opportunity for using high-performance aerospace grade carbon fibres to maximise the tensile strength for composites manufactured from randomly orientated carbon fibre tows and an epoxy matrix. Directed Carbon Fibre Preforming (DCFP) has been used to manufacture preforms with a range of different carbon fibre types, all with a target fibre volume fraction of 50% and fibre length of 45 mm. Results indicate that utilising fibres with higher ultimate strengths does not necessarily result in higher composite component strengths, due to resin dominated failures. However, significant improvements in stiffness can be realised, with a more cost-effective solution achieved by blending two carbon fibre grades together to create a hybrid fibre architecture. The effect of moulding process is also studied to understand the effect on material variability and therefore mechanical performance. Whilst High-Pressure Resin Transfer Moulding (HP-RTM) reduces void content compared to standard RTM, the highest tensile stiffness and strength values are achieved by compression moulding due to a more homogeneous fibre distribution resulting from in-mould material flow. In addition, compression moulding offers moulding cycle times that are ~ 60% shorter than those of conventional RTM for the current application.