SELF-HEALING MECHANISM IN POLYMER COMPOSITE MATERIALS

Abstract

The current self-healing mechanisms are still a long way from being fully implemented, and most published studies have only shown successful damage repair at the laboratory level. The complex nature of these mechanisms makes it difficult to implement them in real-life situations where the component or structure must continue to function. For complete healing, a molecular-level chemical reaction is required with the aid of external stimuli such as heating, light, and temperature change. Existing self-healing mechanisms are almost impossible to implement in critical applications such as 3D-printed products due to the requirements of external stimulations and reactions. The objective of this research is to investigate the strain release behaviour during crack growth of polymeric beams under elastic loads for self-healing. The mechanical behaviour of polymer components has been studied for many years, and their basic features are well understood. In this study, the elastic and plastic responses of 3D-printed beams made of Acrylonitrile butadiene styrene (ABS), thermoplastic polyurethane (TPU), and thermoplastic elastomers (TPE) were investigated under different bending loads. Two types of 3D-printed beams were designed to test their elastic and plastic responses under different bending loads. These responses were used to develop an innovative self-healing mechanism based on origami capsules that can be triggered by crack propagation due to strain release in a structure. The origami capsules, made of TPU in the form of a cross with four small beams either folded or elastically deformed, were embedded in a simple ABS beam. When crack propagation occurred in the ABS beam, the strain was released, causing the TPU capsule to unfold with the arms of the cross in the direction of the crack path. This increased the crack resistance of the ABS beam, which was validated in a delamination test of a double cantilever specimen under quasi-static load conditions. The results showed the potential of the proposed self-healing mechanism as a novel contribution to existing practises primarily based on external healing agents. The self-healing mechanism of TPU and TPE origami capsules has been demonstrated and reported for the first time. These materials achieved a good balance of mechanical strength and self-healing ability. A thicker beam structure tends to yield higher strain energy than do low thickness values for the beam. Since the strain energy release is dependent on how much cracking has propagated, so the higher strain release from the DCB TPU star and roll contributes to the rate at which crack propagation extends.