Investigation of the fibre-matrix interface of glass fibre composites exposed to cryogenic temperatures and cryogenic cycling

The effect of cryogenic cycling between ambient and cryogenic temperatures on the performance of the fundamental fibre-matrix interface of a composite material is a critical parameter in the long-term structural performance of liquid hydrogen pressurised vessels. Therefore, given its pivotal role it is essential to conduct fundamental research into the effects that repeated exposure to cryogenic conditions will have on the fibre-matrix interface. This study investigates the degradation of interfacial shear strength after repeated cryogenic exposure at a fundamental scale, using the microbond technique with subsequent surface analysis. Microbond testing of glass fibre epoxy systems revealed a clear downward trend in interfacial shear strength with increasing cryogenic cycles. Notably, this degradation was significantly mitigated when testing sized fibres in comparison to unsized fibres.