Investigating the Failure Behavior of Over-molded Thermoplastic Composites: Experimental Testing and Numerical Modelling

Over-molded composites are produced by injecting short fiber composites over continuous fiber-reinforced composite inserts through an injection molding process. These composites are suitable for load bearing structural applications because of their high specific strength, stiffness, lightweight nature, and the ability to form complex structures through simple manufacturing processes. However, their performance is highly dependent on the interface adhesion between the short and continuous fiber-reinforced composite inserts. This study investigates the effect of preheating on the load bearing capacity of over-molded composites under tensile and flexural loads using experimental and numerical approaches. The damage mechanism of the over-molded composites is characterized using Hashin and cohesive zone failure criteria within ABAQUS/Explicit to capture the failure mechanisms. The experimental results revealed that preheated over-molded composites demonstrated a significant increase in tensile and flexural properties compared to non-preheated composites. For the non-preheated specimens, the primary failure mechanisms were interfacial debonding, insert delamination, and short fiber composite failure. Conversely, in the preheated specimens, both short and continuous fibers experienced simultaneous damage, owing to the strong cohesive bond formed by preheating. The predicted numerical results align well with the experimental results in terms of load-displacement behavior, strength, and damage morphologies, suggesting that the numerical simulation is a valuable tool for assessing the performance of over-molded composites.