Thanh Trung Do/Dong Joo Lee
The Journal of Mechanical Science and Technology, vol. 23, no. 12, pp.3161-3168, 2009

Abstract : The fiber fabric layers in a preform can be wrinkled or overlapped during a preform loading of the resin transfer molding and thermoforming processes of thermoplastic composites. These fabric discontinuities affect both the mechanical properties and failure mechanisms of those composites. Based on the energy method, the analytical bending modulus is considered and compared to the experimental data for several wrinkling and overlapping patterns. Also, those effects on the bending properties are described through the effective parameters, α, which are the wrinkled parameter and overlapped parameter. It is found that the large fiber content and stress concentrations near discontinuity are the reasons for the larger bending moduli of the wrinkled and overlapped models. As a function of the wrinkled length to the span length (LW/L) and the overlapped length to the span length (LO/L), respectively, the bending strengths and failure mechanisms show the two stages. This is due to not only the failure modes but also the geometrical structures of the fiber fabric preform.

Keyword : Composites; Resin transfer molding; Wrinkling; Overlapping; Bending modulus and strength