Effect of Thermal and External Load on Mechanical Behaviour on CFRP/Aluminium Hybrid Joints

JAXA has been conducted the research to evaluate the fatigue life up to form a certain size of fatigue crack in a CFRP/Aluminum hybrid joint. Thermal stress occurs in the hybrid joints during operation due to the difference of coefficient of thermal expansion between Aluminum and CFRP. In ICAF2023, we presented the experimental and numerical results for the hybrid joint under thermal cycles.

In this study, the mechanically fastened hybrid joint specimens composed of two Aluminum plates and two CFRP plates are prepared. Most of the dimensions of the hybrid joint such as thickness, width of the plates and types and pitch of the fasteners and etc. are same as those evaluated in the previous research. The cyclic thermal and external loads are simultaneously applied to the hybrid joint and stress and strain on the Aluminum plate are evaluated experimentally and numerically. From the behavior of the elastic strain, which is the total strain minus the thermal strain, it is shown that when thermal load and external load are coupled, the hysteresis loop becomes larger than when only the external load is repeatedly applied. In addition, it is shown that the strain and stress around the fastener holes in the top row through the load direction are high, and this could be a critical area for fatigue failure.