Experimental studies were performed on the strain energy storage behaviour of aerospace grade PEEK
and toughened epoxy carbon fibre-reinforced composite prepreg laminates having identical fibre
content. The strain energy stored up to failure was recorded at the highest point of deflection for static
three point bending (3PtB) samples laminates with different thicknesses. Ductile and brittle behaviors
at failure have been the key focuses of this study therefore cyclic loading tests were also performed.
Firstly, high strain 3PtB fatigue loading was carried out on the two prepregs with identical quasiisotropic
stacking sequences, and secondly in order to characterise the plasticity parameters for the two
laminates cyclic shear tests at high strain levels was carried out. The results have shown that the strain
energy storage characteristics of the PEEK laminates are much better than those of the epoxy laminates
in several ways; such as the independence of the strain energy storage level to thickness. Furthermore,
at the same level of applied stress, the PEEK laminates tend not to lose strain energy compared to the
toughened epoxy laminates. This study shows that the thermoplastic nature of the PEEK gives it an
improved plasticity level which enhances its strain energy storage capability. PEEK carbon laminates
are therefore serious candidates for spring applications
