Effect of environmental conditions on failure mode and tensile strength of bonded joints

With the increasing use of composite materials, their adhesive joints are affected by different environmental factors. To investigate the tensile performance of composite material adhesive structures in complex environments, this paper conducted tensile strength tests on four different types of structural adhesives in different environments, using scanning electron microscopy (SEM) to analyze the microstructure of the adhesive failure interface and have studied the failure mechanism under different environmental conditions. Finally, the finite element method (FEM) is used to explain the adhesive failure process in typical environments. The results showed that compared to the room temperature dry (RTD) environment, the tensile performance of the adhesive did not decrease in the elevated temperature wet (ETW) environment but significantly decreased in immersion environment and oil immersed environment. The SEM and FEM results respectively indicated that the bubbles and pores that appear under different environmental erosion were the main reasons for the decrease in the tensile strength of the adhesive. The failure starting point of the adhesive in typical environments was located the center of the adhesive.