Solid epoxy resin systems for automated composite manufacturing
Neptun Yousefi, Anthony Evans, L.T. Harper, Henry A. Maples, T. G. James, Alexander Bismarck
Abstract
Thermosetting resins were formulated by mixing solid epoxy components, hardener and accelerator at elevated temperature. These mixtures were ground into uncured, solid resin powders and dispensed onto carbon fibres using a powder printer prior to vacuum curing. Using accelerators reduced curing time from 8 h to 16 min. Manufactured cross-ply carbon fibre laminates (0°/90°/0°) had comparable mechanical properties to composites manufactured using a liquid resin system. Tack behaviour of solid epoxy resin formulations was investigated and results compared to a conventional liquid resin system. Master curves of the storage and loss moduli of both solid and liquid resin formulations were generated by applying time-temperature superposition to shear moduli between 1 and 100 rad/s at multiple temperatures. This approach was used to determine optimum processing parameters to enable resin tack for automated fibre placement, demonstrating the importance of temperature control with respect to deposition rates.