Effects of transient dynamic loading on the energy absorption capability of composite bolted joints undergoing extended bearing failure

Carbon fibre reinforced polymer (CFRP) materials are widely used in transport aircraft. Crashworthiness requirements demand sufficient energy absorption capacity, especially in the fuselage structure. In a recently-proposed approach, specifically-designed “tension absorber” joints utilize tension loads for energy absorption via progressive bearing failure. For further development of the concept, experimental tests are performed on pin- joints in quasi-isotropic CFRP material, under transient dynamic loading at 3 m/s. Investigated parameters are laminate thickness, stacking sequence and pin diameter, and the results are evaluated using the performance parameters ultimate bearing strength, mean crush stress and mass-specific energy absorption. A strong relation between the ratio of pin diameter to laminate thickness, D/t, and the performance parameters is found. Compared to previous results for quasi-static loading, the ultimate bearing strength is increased whereas the mean crush stress and mass-specific energy absorption are reduced. Digital image correlation and computed tomography analysis reveals the mechanisms behind the observed trends. The results provide a basis for further optimization of energy-absorbing joints and validation of finite element models.