Existing self-healing mechanisms are still very far from full-scale implementation, and most published work has only demonstrated damage cure at the laboratory level. Their rheological nature makes the mechanisms for damage cure difficult to implement, as the component or structure is expected to continue performing its function. In most cases, a molecular bond level chemical reaction is required for complete healing with external stimulations such as heating, light and temperature change. Such requirements of external stimulations and reactions make the existing self-healing mechanism almost impossible to implement in 3D printed products, particularly in critical applications. In this paper, a conceptual description of the self-healing phenomenon in polymeric structures is provided. This is followed by how the concept of self-healing is motivated by the observation of nature. Next, the requirements of self-healing in modern polymeric structures and components are described. The existing self-healing mechanisms for 3D printed polymeric structures are also detailed, with a special emphasis on their working principles and advantages of the self-healing mechanism. A critical discussion on the challenges and limitations in the existing working principles is provided at the end. A novel self-healing idea is also proposed. Its ability to address current challenges is assessed in the conclusions.
The response of polymeric beams made of Acrylonitrile butadiene styrene (ABS) and thermoplastic polyurethane (TPU) in the form of 3D printed beams is investigated to test their elastic and plastic responses 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 origami capsule-based novel self-healing mechanism that can be triggered by crack propagation due to strain release in a structure. Origami capsules of TPU in the form of a cross with four small beams, either folded or elastically deformed, were embedded in a simple ABS beam. Crack propagation in the ABS beam released the strain, and the TPU capsule unfolded with the arms of the cross in the direction of the crack path, and this increased the crack resistance of the ABS beam. This increase in the crack resistance was validated in a delamination test of a double cantilever specimen under quasi-static load conditions. Repeated test results demonstrated the effect of self-healing on structural crack growth. The results show the potential of the proposed self-healing mechanism as a novel contribution to existing practices which are primarily based on external healing agents.
printing is now one of the most essential industrial production technologies. However, the most commonly used material in Fused Deposition Modelling (FDM) technology is Acrylonitrile Butadiene Styrene (ABS), has excellent mechanical properties. During the last few decades, researchers have focused on issues related to self-healing materials. However, because of their low mechanical strength, self-healing materials have yet to find widespread application. In this work, the behaviour of polymeric beams made of TPU "roller" materials and their responses under load is developed. One type of 3D-printed beam was designed to test different force ranges (0-0.73575 N) and deflection resolutions (15 mm-19 mm) with respect to the length. An assessment was also made of the self-healing mechanism, which encompasses the intrinsic and extrinsic techniques for each application. In terms of an extrinsic procedure, external healing agents such as micro-capsules were introduced into the system. But we came up with a way to estimate the length of the crack tip based on the relationship between the force applied and the load frame's movement. Origami capsule-based healing systems are a well-known technology that has multiple uses in smart materials.
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