This study investigates the mechanical behavior and interfacial reliability of CFRP/PVC foam core sandwich composites manufactured using an adhesive-free co-curing process. Building upon previous work that verified interfacial bonding integrity through ultrasonic non-destructive evaluation and ASTM C297 flatwise tensile tests, additional experimental and numerical investigations were conducted to further assess the structural feasibility of eliminating the adhesive layer. Finite element analysis based on the ASTM C297 configuration was performed to validate the interfacial modeling approach, showing excellent agreement with experimental tensile results, with prediction errors within 2% for the UD specimens. To evaluate structural performance under more realistic loading conditions, three-point bending tests were carried out in accordance with ASTM C393, and the results revealed that, regardless of the presence of an adhesive film, flexural failure was predominantly governed by face-sheet and/or core failure for most configurations, while Mode-II–related interfacial shear effects did not dominate the overall failure response. Interfacial delamination was observed only in specific UD configurations under relatively high flexural load levels, which was attributed to localized stress concentrations arising from fiber orientation rather than insufficient interfacial bonding strength. A simplified quantitative assessment based on classical sandwich beam theory further demonstrated that the estimated face-sheet bending stresses approached 86–103% of the CFRP strength, whereas the estimated interfacial shear stresses remained only about 11–13% of the interfacial shear strength obtained from flatwise tensile tests. These findings confirm that, for sandwich structures with CFRP face sheets thinner than 1 mm, the flexural response is governed primarily by the mechanical limits of the face sheets and core rather than by Mode-II interfacial fracture, and overall demonstrate that adhesive-free co-cured sandwich composites with woven CFRP face sheets can achieve sufficient interfacial reliability and structural performance for lightweight load-bearing applications without the use of an adhesive film.

Keywords: Adhesive-free, Co-curing, CFRP sandwich, Finite element analysis