Effects of thermal residual stresses on failure of co-cured lap joints with steel and carbon fiber–epoxy composite adherends under static and fatigue tensile loads

A co-cured joint, which uses excess resin extracted from the composite material (or the polymer material) as the adhesive, has several advantages compared with the adhesively bonded joint. It has no need of the surface treatment of the composite adherend and any adhesive for bonding. In addition, its manufacturing process is very simple because the bonding process is achieved during the curing process of the composite adherend. Thermal residual stresses are important in analyzing failure of the co-cured joint because composite materials are different from metal alloys in thermal and mechanical properties. In general, effects of the thermal residual stresses on failure of the adhesive joint are analyzed through experimental and analytical results.Therefore in this paper, two design parameters, namely the surface roughness of the steel adherend and the stacking sequence of the composite adherend, are considered for static and fatigue tensile tests of the co-cured single and double lap joints. Stress distribution at the interface between the two adherends is used to analyze failure of the co-cured lap joints through the finite element method. Based on the stress distribution, two failure criteria, namely the three-dimensional Tsai–Wu failure criterion and the Ye-delamination failure criterion, are considered to predict the tensile load bearing capacity of the co-cured lap joints. Finally, effects of thermal residual stresses on failure of the co-cured single and double lap joints with the steel and composite adherends under static and fatigue tensile load conditions are presented through comparing the experimental and analytical results.