Strengthening and self-healing of natural fiber composites via PLA core-shell nanofibers as healing agent carrier

The resin-rich region between the fiber laminates of a fiber-reinforced composite is susceptible to matrix damage impeding the composite's integrity. Hence, this study intends to interlayer core-shell poly(lactic) acid (PLA) nanofibers between the flax fibers as a preventive and reactive mechanism to matrix damages in the resin-rich area. The nanofibers prevent premature damage by suppressing or mitigating crack propagation and in the event of damage to the nanofibers, it reacts by releasing the encapsulated healing agent. Upon interlayering the flax fiber laminates with self-healing core-shell nanofibers, the flexural modulus exhibited an increment of 31% whereas the short beam strength improved by 19%. Self-healing traits of the composites were assessed by subjecting the composites to repeated flexural or short beam strength tests for several load cycles. Upon initial damage to the composites, the composites exhibited a full retention and improvement in mechanical properties. The self-healing composites were also able to withstand more loading cycles than the conventional composite under repeated short-beam strength tests. Under both configurations, the damaged self-healing composites exhibited a residual strength greater than or equivalent to the ultimate strength of a pristine flax fiber composite.