Compression molding of warp-knitted PET/GF based composites: Influence of forming temperature on consolidation quality and impact properties

The objective of this work has been to study the influence of processing temperature during compression molding on the consolidation quality and mechanical properties of warp-knitted fabric-based composites made of commingled yarns containing glass fiber (GF)/polyethylene terephthalate (PET). The consolidation quality in terms of void content and uniformity of fiber distribution was studied on unidirectional and cross-ply laminates. The mechanical properties studied were flexural strength, flexural modulus, Izod impact strength, and drop-weight impact resistance. The influence of forming temperature on fiber-matrix adhesion was studied by measuring the transverse flexural strength and SEM analysis. SEM analysis was also used to analyze the mode of fracture during impact. The results in this paper suggest that consolidation quality as defined by fiber distribution is strongly dependent on molding temperature. The transverse strength increased significantly with processing temperature, indicating an increase in fiber-matrix interfacial adhesion with increasing processing temperature. The increased interfacial adhesion influenced the Izod strength and drop-weight impact behavior of the laminates.