Experimental characterisation of the in-plane shear behaviour of UD thermoset prepregs under processing conditions

The in-plane shear behaviour of an uncured composite material (i.e. prepreg sheet, dry fibre preforms etc) is one of the key parameters that influences wrinkle generation in advanced composites manufacturing processes such as automated fibre placement (AFP) and thermoforming. However, there is no standardised test method for the characterisation of uncured unidirectional prepreg subjected to pure shear loading. In this paper, a 10° off-axis tensile test is developed, and the method's suitability is demonstrated on two different materials. The mechanical response is analysed over a range of testing rates and temperatures that are consistent with the real manufacturing process parameters. The results demonstrate the feasibility of the test method for extracting relevant material characteristics and the strain-rate and temperature dependency of the material response.