Modeling of the Healing Process of Polycaprolactone-Interleaved Carbon Fiber–Reinforced Composites

Thermoplastic interlayer provides an excellent opportunity to heal/repair inhomogeneities or damage in composites. By melting the thermoplastic interlayer, the damage can be filled, thereby increasing the service life of the composite part. In this paper, we analyzed the healing process of carbon fiber–reinforced epoxy matrix composites with a thermoplastic, structured interlayer (created by FFF 3D printing method) during ENF tests. We observed the effect of the concentration of the interlayer and the applied surface pressure on the properties of the healing process. The results show that increasing interlayer content can improve maximal healing efficiency from 96.6% ± 0.3% (25 A/A%) to 98.8% ± 0.3% (100 A/A%). While healing pressure does not affect the healing efficiency significantly, it can reduce the optimal healing time. In all cases, healing efficiency has an optimum, after which increased healing time leads to a decrease. To gain a deeper understanding of the process, we have adapted a control theory model, which helps in the selection of optimal process parameters for healing, which can be utilized for other thermoplastic interlayer-based healing methods.