Stress, Holes and Chemicals: Environmental Effects on Carbon Fibre Reinforced PEEK Laminates

Abstract

Carbon fibre/PEEK laminates were immersed in several liquid chemical environments including aviation jet fuel, water, Skydrol hydraulic fluid, and dichloromethane. They were simultaneously subjected to tensile, flexural and (in some cases) compressive loads. Comparison experiments were performed with samples in dry air. The rate of sorption of the liquid environments into quasi- isotropic laminates containing small circular holes was studied as a function of the (constant) strain applied. The specimens were then broken in tension. Strength and modulus retention were noted. The nature and magnitude of the load and of the environment had little effect on the failure mode, but considerable effect on the strength retention, and damage was sometimes initiated in the vicinity of the holes. Critical strain levels for damage initiation in dichloromethane are reported. A few results are also reported for unidirectional laminates, without holes.