Investigation on the Wrinkling Limit Diagram of self-reinforced polypropylene woven composite at room temperature

Wrinkling is one of the most common instabilities that occur during forming of prepreg and consolidated composite sheets. It is generally undesirable as it decreases the strength of the parts and gives an unacceptable appearance to the final product. In this study occurrence of wrinkling during forming of self-reinforced polypropylene (SRPP) is investigated by application of uniaxial extension test on specially designed samples. These specimens were extended uniaxially by an INSTRON machine until wrinkles appeared on their surface. Principal strains evolution have been recorded by an in-situ 3D photogrammetric measurement system and then plotted in strain space. This determined Wrinkling Limit Diagram (WLD) which could be utilized to distinguish between safe and wrinkled regions during forming of pre-consolidated woven SRPP. In addition, the forming behaviour of pre-consolidated woven sheets of SRPP during uniaxial extension will be elucidated in terms of major and minor strains development.