Synergistic enhancement of interfacial and anti-hydrothermal properties of HMCF reinforced Cyanate Ester composites by matrix stiffening and interphase optimization

Cyanate ester (CE) matrix and high-modulus carbon fiber (HMCF) surface were modified by epoxy-functionalized polyhedral oligomeric silsesquioxane (POSS), and the correlations of stiffened matrix and optimized interphase with interfacial and anti-hydrothermal properties of various HMCF/CE composites were investigated. The improved tensile modulus and reduced free volume contributed to decreasing coefficient of thermal expansion (CTE) of POSS-CE (PCE) matrix, and a layer of POSS nanoparticles on fiber surface caused the enhancement of surface chemical activity and roughness of POSS-HMCF (P-HMCF), which resulted in 30.9%, 48.9% and 79.8% increment of interfacial shear strength (IFSS) in P-HMCF/PCE composites from the broader modulus intermediate layer, compared to HMCF/CE, HMCF/PCE and P-HMCF/CE composites. After aging 30 days, P-HMCF/PCE composites exhibited the minimum moisture uptake (0.80%) and the highest interlaminar shear strength (ILSS) retention (84.9%), and thickness broadening and cracks propagation at interphase were hardly generated based on the quantitative analysis of interphase modulus distribution, which was attributed to suppressive moisture uptake of PCE matrix and superior interfacial adhesion between resin and P-HMCF.

Automated summary

This study investigated the correlations between stiffened matrix and optimized interphase with interfacial and anti-hydrothermal properties of various HMCF/CE composites by modifying the CE matrix and HMCF surface with epoxy-functionalized POSS. The addition of POSS nanoparticles on the fiber surface enhanced the surface chemical activity and roughness, resulting in improved interfacial shear strength in P-HMCF/PCE composites. After aging, these composites exhibited minimal moisture uptake and retained high interlaminar shear strength, with reduced thickness broadening and cracks propagation at the interphase.