Design of a set-up for measuring the residual compressive strength after high load and high cycle compression fatigue on CFRP

A new testing set-up to measure the compressive strength of continuous fibre composite materials (CFRP) under both static and fatigue loadings is described. A specific symmetric sandwich beam with CFRP face sheets is used with a four-points bending set-up. Its mechanical design is carried out by fine Finite Element Analyses (FEA) to ensure that the failure mode is axial compression by fibre micro-buckling. Precise comparisons between numerical simulations and experimental quasi-static experimental results are found to be sound, validating the FEA model. The latter is used to design the sandwich beam in terms of strength and stability criteria. Finally, a high cycle fatigue campaign (107 cycles) with high modulus CFRP skins demonstrates the performance of the set-up. Repeatable results and acceptable failure modes are obtained.