Mechanical, wear and friction characteristics of UF-DCPD Microcapsule based self-healing epoxy nanocomposites

In this study, hybrid epoxy composite was fabricated by using LY556 epoxy resin and HY951 epoxy hardener, with UF-DCPD self healing microcapsules 2, 4 and 6 wt.% and TiC particulates 2.5 and 5 wt.%. The mechanical properties, including tensile strength, elastic modulus, elongation, and tribological properties wear rate, and coefficient of friction were measured as well as nanoindentation properties such as hardness, elastic recovery (%), H/E ratio, and H 3 /E 2 (GPa). The 2.0wt.% microcapsules + 5wt% of TiC showed the highest elastic modulus, hardness, elastic recovery, H/E and H 3 /E 2 among other samples, which demonstrated the highest deformation resistance. As the content of the microcapsule increased, the elastic recovery decreased for microcapsules only composites, and as the TiC loading increased, the elastic recovery improved. The highest coefficient of friction and wear rate were observed for neat epoxy, which decreased gradually with increasing amount of reinforcement content, with a minimum friction coefficient of 0.32 for 6 wt.% microcapsules and 5 wt.% TiC). The wear trend was confirmed by the wear track results, and Sample 10 showing the shallowest wear track (8 µm). This equated to an 88.5% reduction in the specific wear rate (36.5 × 10 -4 mm 3 /N·m to 4.2 × 10 -4 mm 3 /N·m). Based on fracture toughness result the maximum healing efficiency 61.2% was found in sample 6. These SEM observations indicated mixed mode wear with evidence of ploughing, adhesive transfer, smearing, micro-cracking and delamination and these tensile fractography observations indicated mixed brittle-ductile failure due to interaction of cracks with TiC and micro-capsules.