Effect of moisture on the mechanical properties of CFRP-wood composite: An experimental and atomistic investigation

Adhesive bonding of fiber-reinforced polymers (FRP) to wood has been proven as a general way to achieve reinforcement and rehabilitation for wood structures. Although a significant mechanical enhancement can be acquired by using such approach, there exists a big concern about the long-term performance of the FRP-wood composite, especially under the effect of moisture. In this paper, both experimental and atomistic approaches are adopted for investigating the moisture effect on the entire FRP-wood composite system. Macroscopic mechanical tests show that its mechanical properties and its fracture behaviors notably change at different levels of ambient humidity. From an atomistic perspective, molecular dynamics (MD) simulations reveal that water molecules significantly reduce the adhesion energy between wood and epoxy. Results from experimental and numerical studies imply that the strength of the FRP-wood interface critically determines the mechanical performance of the entire system. The water molecules absorbed at the interface are crucial to the durability of multi-layer systems and a general mechanism governing the failure modes of such systems is found.