Bioinspired self-healing of advanced composite materials

Lightweight, high strength, high stiffness fiber reinforced polymer composite materials are leading contenders to improve the efficiency and sustainability of many forms of transport. They offer immense scope for incorporating multifunctionality due to their hierarchical internal architecture. One limiting factor in their wider exploitation is relatively poor performance under impact loading, a crucial aspect of any safety critical design, leading to a significant reduction in strength, stiffness and stability. This results in conservative design and higher mass structures. Self-healing has the potential to mitigate damage resulting from impact, thereby improving design allowables or offering other benefits such as reduced maintenance and inspection schedules. The work presented in this paper shows that either compartmentalised hollow-fiber or continuous vascular network self-healing approaches can be used for the repair of advanced composite structures. In the nearer term, the specific placement of self-healing plies or individual fibers to match a critical damage threat has been shown to repair internal matrix cracking and delaminations throughout the thickness of a laminate when assessed in both a flexural and compressive loading state. In the longer term, integration of a pervasive, circulatory vascular network within the foam core of a composite sandwich structure has also been shown to offer a marked benefit. The network has negligible influence on structural performance whilst being able to provide reattachment of the foam core and laminate skin after impact damage. In the case studied, a sizeable recovery in flexural and compression after impact strength, and restoration of primary failure mode was observed. Such systems offer significant potential for restoring structural integrity to a composite component during service and prolonging residual life after a damage event.