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Out-of-autoclave prepregs require a two-step cure cycle. The first step is a low temperature cure to consolidate the laminate and build sufficient green strength to proceed to the second step, a free-standing post-cure at traditional autoclave temperatures to fully cross-link the resin. Process modeling can help design a robust cure cycle to avoid scrapping large parts in production. The focus of this article is to develop the cure kinetics, viscosity, and glass transition temperature models for two commercially available out-of-autoclave epoxy resins. Since the cure kinetics model is the basis for all other thermal models, the cure kinetics model was validated using a one-dimensional heat transfer analysis on thick prepreg laminates. Finally, the out-of-autoclave resin models were compared to a traditional autoclave resin system to highlight the difference in resin reactivity for out-of-autoclave processing.

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 wrinkles 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.