Defects in woven preforms: Formation mechanisms and the effects of laminate design and layup protocol

Defects, such as in-plane waviness and out-of-plane tow wrinkles, cause significant reductions in the mechanical performance of RTM-manufactured composite parts based on woven preforms. To avoid this problem and achieve a greater acceptance rate in industrial processes, the mechanisms behind these defects must be understood. This paper presents a mechanism for the formation of these defects, which is supported through layup trials of woven preforms. Laminate design and layup protocol were found to be significant drivers behind the mechanism. Defect severity can be controlled through intelligent stacking sequence design and reducing ply bridging by manual forming actions and ply-ply adhesion during layup.