Interlaminar shear strength and self-healing of spread carbon fiber/woven carbon fiber hybrid reinforced epoxy resin laminates containing microcapsules

The objective of this study is to improve the mechanical properties of self-healing carbon fiber reinforced polymer (CFRP) with microcapsules (MCs) incorporating healing agents, in order to achieve superior mechanical properties and healing efficiency. The approach to improve the mechanical properties is to hybridize spread carbon fiber (SCF) and woven carbon fiber (WCF) as reinforcements. The interlaminar shear strength and the healing efficiency of the self-healing SCF/WCF hybrid laminates were evaluated by short beam shear tests, and then compared with those of self-healing SCF/EP laminates and self-healing WCF/EP laminates. Moreover, the finite element analysis (FEA) using a representative volume element (RVE) model of the SCF/WCF hybrid laminates containing MCs was performed to evaluate the elastic properties and the internal stress and reveal the relation between them and microstructure. Furthermore, we performed the FEA of short beam shear test using the elastic properties predicted from the RVE models and verified the validation of the RVE model by comparing the analytical results with the experimental results. The experimental results showed that the hybridization of SCF and WCF can be effective for improving mechanical properties of self-healing CFRP laminates compared to those of self-healing SCF/EP laminates. However, the self-healing SCF/WCF hybrid laminates did not present sufficient healing efficiency due to the large transverse cracks in the WCF layers. Therefore, in order to improve healing efficiency, it is necessary to suppress the large crack propagation in the WCF layer. The analytical results indicated that the stress concentration occurred in the WCF layer and could be mitigated by increasing the thickness of the SCF layer. The experimental results and analytical results were in good agreement. Therefore, the RVE model used in this study effectively predicted the properties of the self-healing CFRP laminates and provided microstructure design guidelines for achieving superior mechanical properties and healing efficiency.