Forming of Hybrid (CF UD Prepreg - Advanced SMC) Composite Layups

Combining continuous unidirectional (UD) prepreg and advanced discontinuous long fiber-based sheet moulding compound (ASMC) in a hybrid component is advantageous for applications where cost and environmental impact of the manufactured part are of significance. Previous works have focused on the flow/compaction of ASMC and its interaction with continuous fibres at high pressures. However, little is known about the forming behaviour of such layups. This work investigates the formability of hybrid carbon fibre UD-ASMC composite layups. The deformation mechanisms during forming and their interactions are investigated experimentally. Forming simulations are conducted alongside experimental tests under varying layup configurations. The results show that the hybrid layup combinations investigated exhibited poor forming characteristics. This was due to the high interply friction properties of the UD-ASMC interface, which, in turn, restricted the intraply shear of the hybrid stack. A strong correlation between the numerically predicted forming outcomes and experimentally formed parts demonstrates that generic FE-solvers can provide a first estimate of the forming outcome when coupled with a good understanding of the underlying deformation mechanisms. However, these methods are computationally expensive and are better suited for detailed evaluations rather than for use in design applications.