Classification of progressive failure and mechanical behavior of dissimilar material hybrid joints at varying temperatures

This research illustrates the progressive failure mechanisms and variation in the mechanical behavior of dissimilar materials hybrid joints at elevated temperatures. For this purpose, a novel in-situ data fusion scheme was developed from experimental analysis which was validated through a coupled computational approach. The hybrid joint consisted of CFRP/Al worksheets joined through a steel bolt. The experimental analysis revealed distinct failure mechanisms in worksheets, i.e., yielding in Al sheet and a mixed failure mode in CFRP sheet while no signs of failure were observed in the steel bolt. Further, the progressive damage in the CFRP sheet was classified as a three-staged process which comprised elastic strain phase, crack initiation and progressive damage phase, and unstable fracture phase by correlating the temperature (Infrared Thermography) and strain variations (Digital Image Correlation). Further, degradation in mechanical behavior from room temperature was evaluated at three elevated temperatures, i.e., 50 °C, 75 °C, and 100 °C. A significant drop in mechanical properties (maximum strength and nominal stiffness) was noticed at high temperatures while a transition in failure mode was also evident (ply bending and pronounced fiber breakage) in comparison to the joints tested at room temperature. In computational analysis, Tsai–Wu, Maximum Stress, and Puck's static failure criteria were coupled with the element deletion model to ascertain the critical ply and progressive damage in the joint. The experimental results were found in good agreement with the computational results in terms of critical ply and load-carrying behavior. In summary, this research helps to understand the progressive failure and variation in mechanical behavior about high temperatures in hybrid joints which can be extended to other dissimilar materials configurations as well.