Self-Healing Materials as New Biologically Inspired Materials

Abstract

Lightweight, high strength fibre-reinforced polymeric composites are leading materials in many advanced applications including biomedical components. These materials offer the feasibility to incorporate multi functionalities due to their internal architecture, heterogeneity of materials and the flexibility of combining them using currently available fabrication methods. In spite of the excellent properties of these materials, their failure is still a questionable and not well predicted event. Delamination, debonding and micro-cracks are only some of the failure mechanisms that affect the matrices of polymer based composites. More complex cases exist with the combination of multiple failure mechanisms. In such cases a self-repairing mechanism that can be auto-triggered in the matrix material once the crack has been formed, would be very beneficial for all the applications of these materials, reducing maintenance costs and increasing their safety and reliability. Self-healing materials have been studied for more than a decade by now, with the specific objective of reducing the risks and costs of cracking and damage in a wide range of materials. Different approaches have been taken to create such materials, depending on the kind of material that needs to be repaired. The most popular methods developed for polymers and polymer reinforced composites are considered in this review. These methods include materials with micro-capsules containing a healing agent, and composites with matrices that can self-heal the cracks by repairing the broken molecular links upon external heating. While the first approach to healing has been widely used and studied in the past decade, in this review we focus on the second approach since less is reported in the literature and more difficult is the development of the materials based on such a method.