Effects of Nanofiber Interleaving on the Strength and Failure Behavior of Co-Cured Composite Joints with Fiber Orientation Mismatch

This study investigates the effect of nanofiber interleaving on the mechanical performance of co-cured composite lap joints with effective fiber orientation mismatch at the joint interface. Joint configurations were defined by dominant yarn orientations at the bond line—denoted as (lower-substrate|upper-substrate)—and tested in (0|0), (90|90), and mismatched (0|90) setups using an 8-harness satin (8HS) fabric architecture, with and without nanofiber interlayers. Mechanical testing revealed an over ~25% reduction in lap shear strength for the (0|90) configuration relative to the matched (0|0) and (90|90) joints. Nanofiber interleaving effectively restored this loss, achieving strength levels comparable to the matched cases. Statistical analysis using two-way ANOVA and ANOM confirmed that both fiber orientation and nanofiber interleaving significantly influence joint strength, with a notable interaction effect (p < 0.001). Fractographic analysis further showed that nanofibers enhanced delamination resistance by stabilizing crack paths and suppressing crack jumps at crimping sites, especially in (0|90) joints where 0/90 yarn intersections are prone to early failure. These findings underscore the role of nanofiber interleaving in mitigating mismatch-induced failure mechanisms and improving the structural integrity of composite bonded interfaces.