抄録
Adhesive bonding is increasingly adopted in automotive and aerospace industries due to its potential for weight reduction and recyclability. Recent studies have reported that the fracture toughness of adhesively bonded joints can vary due to the surface geometry of adherends, even when cohesive failure occurs within the adhesive layer. However, the underlying mechanical mechanism for this variation remains unclear. In this study, we investigate how periodic surface roughness affects the strain energy release rate (SERR) during cohesive crack propagation using finite element analysis. The surface geometry is simplified as periodic roughness with varying pitch and height. The SERR distribution along the crack front is evaluated, and periodic minima, which act as rate-limiting points for crack propagation, are extracted. A response surface model is constructed to express these minimum values as functions of geometric parameters. A comparison with experimental fracture toughness obtained from double cantilever beam (DCB) tests reveals a significant negative correlation between the response surface minimum and measured toughness. Furthermore, strain energy analysis shows that increased surface roughness leads to a redistribution of elastic energy from the adhesive to the adherend, indicating a reduction in stress concentration. These findings suggest that surface morphology optimization can contribute not only to preventing interfacial failure but also to improving cohesive fracture resistance, offering a new design perspective for adhesively bonded joints.
