Sheet forming of thermoset composites is a promising method to achieve reduction in manufacturing time and therefore cost. The behaviour of weaves has been thoroughly investigated and the PJN assumption is widely used. Cross-plied UD prepreg may initially show similar behaviour to weaves; however, the complete deformation is more complex, including slippage. Thus, the forming of cross-plies can offer a possibility of increased drapability compared to woven fabrics, but imposes difficulties in predicting forming limits and final fibre angles. The work presented herein aims to characterise the in-plane properties of cross-plied UD prepreg with the bias extension test method. Understanding the deformation modes and its limits could reduce the number of iterations from idea to component in production. The forming of a preplied stack depends on many parameters. The study shows that a higher crosshead rate consequently results in a higher load response. In addition, the type of deformation mode changes due to both speed and temperature.
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