Crosslinker-enhanced epoxy resin improves torsional resistance of carbon fiber braided tubes: multiscale analysis of failure mechanisms

This paper examines torsional failure mechanisms in braided carbon fiber epoxy tubes incorporating crosslinker modified matrices. Three epoxy formulations were tested: non crosslinked resin, resin containing 10 wt% DDS crosslinker, and resin containing 20 wt% DDS. Specimens were fabricated using vacuum assisted resin infusion molding. Torsion testing demonstrated that DDS addition increased stiffness by 19.8 % and peak torque by 42.1 % versus non crosslinked systems, though higher DDS content reduced failure strain. A multiscale finite element model integrating yarn homogenization and cohesive zone interfaces achieved over 95 % experimental correlation. Progressive damage analysis revealed three sequential failure stages: initial resin cracking at yarn intersections, subsequent interfacial debonding from stress mismatch, and ultimate yarn fracture. The 10 wt% percent DDS formulation optimized strength stiffness toughness balance, while stress concentrations at yarn crossovers with local enhancement factors of 1.8–2.2 were identified as critical failure initiation sites. These results confirm that crosslinker enhanced interfaces significantly improve torsional resistance.