Relationship between mechanical performance and microstructure in composites fabricated with flow-enhancing fabrics

The resin transfer moulding process involves the long-range flow of resin into a closed mould which is filled with dry reinforcement. High-performance composites require a high volume fraction of fibres, which results in low porosity of the fibre pack and therefore slow rates of mould filling. Commercial reinforcement fabrics are becoming available which promote faster resin flow than conventional fabrics, by engineering regions of large pore space into the reinforcement stack. However, theoretical models of the property-microstructure relationships have indicated that resin-rich areas (corresponding to filled large pore space) and fibre clustering will lead to degradation of the mechanical performance of the laminate. This report describes a series of compression and interlaminar shear tests on a range of twill-weave fabrics having 'flow-enhancing' tows substituted in the warp direction. The results provide some experimental support for existing theoretical models.