Experimental and numerical investigation of the traction-separation law of mode II fracture in single-edge ultrasonic welding in polypropylene composite reinforced by glass fibers

The use of welded joints in composite structures with reinforced fibers has rapidly increased owing to their advantages in terms of strength-to-weight ratio, design flexibility and ease of production. Herein, the generalized progressive damage model is numerically and experimentally studied to predict the degradation process in end notch flexure (ENF) composite specimens welded by the ultrasonic method. In numerical modeling, a trapezoidal traction-separation model that expresses the embedded process zone (EPZ) is developed using three data reduction methods of the compliance calibration method (CCM), classical beam theory (CBT) and compliance-based beam method (CBBM), and formulated by combining failure and damage mechanics. Finally, the force-displacement diagrams obtained from experimental investigations and the force-displacement diagrams extracted from numerical modeling are compared. The results demonstrate that the models extracted using CBBM and CBT methods make accurate predictions compared to the CCM method.