Study on mechanical properties and tensile failure mechanism of outer/inner-layer bamboo laminates prepared by adhesive film

To overcome the problem of poor adaptability of the traditional dipping process in the forming of special-shaped curved surface, this study explored a preparation method of bamboo-based composite materials based on epoxy resin adhesive film. The outer-layer bamboo laminate (OLBL) and the inner-layer bamboo laminate (ILBL) were fabricated using bamboo outer-layer slices and bamboo inner-layer slices as materials, bonded with solid epoxy resin film. A systematic comparison of their mechanical properties and tensile failure mechanisms was conducted through tensile testing, three-point bending tests, SEM observation, surface polarity and functional group analysis. Results demonstrated that the OLBL exhibited superior mechanical performance, with tensile strength, flexural strength, and fracture toughness reaching 3.4, 1.7, and 1.8 times those of the ILBL, respectively. The OLBL primarily failed via fiber pull-out and interfacial debonding due to weak van der Waals interactions, whereas the ILBL showed brittle fracture attributed to strong polar bonding and enhanced interfacial adhesion. This study clarifies the mechanical divergence between bamboo outer-layer and inner-layer as functionally distinct structural units, providing a scientific basis for the performance-oriented structural design of bamboo-based composites.