REFERENCE: ICF100613OR FREE EDGE AND INTERACTION EFFECTS ON THE STRENGTH OF FINITE-SIZED INTERFACE BONDS Henrik Myhre Jensen Department of Solid Mechanics, Building 404 Technical University of Denmark DK-2800 Lyngby, DENMARK ABSTRACT A fracture mechanics based analysis of the strength of a bond between a thin plate and a substrate is presented. The bond edge is regarded as a crack front, which is loaded under combined mode I, II and III conditions. A numerical procedure is used to study crack initiation. Results for bond strength are presented for bonds close to the plate edges and for closely spaced bonds. KEYWORDS Bond fracture, interface fracture, three dimensional fracture, fracture criteria, crack shape. INTRODUCTION A framework based on linear elastic interface fracture mechanics for studying initiation and propagation of cracks in bonds of arbitrary shape was formulated in Jensen [1]. The work is an extension of previous fracture mechanics based models for predicting the strength of spot welds (e.g. Pook [2] and Zhang [3]). Adhesive bond failure was studied in Reedy and Guess [4] where bond strengths were correlated to the stress intensity factor for the singular stress field at the interface corner as in conventional linear fracture mechanics. The trends in the bond strength dependence on the thickness of the adhesive layer were well captured with this model. Other alternative approaches for studying interface bond failure include methods based on cohesive zone modelling such as Lin et al. [5] where these models have been applied to study fracture in weld joints. The problem analysed is sketched in Fig. 1. A thin plate is bonded to a substrate in a region or several regions of arbitrary shape. The plate is loaded in its plane by a constant normal traction. The bond edge is treated as an interface crack front, and the energy release rate, the decomposition into modes I, II and III and the mixed mode fracture criterion is based on the interfacial fracture mechanics concepts in Jensen et al. [6]. The radius of curvature of the crack front is taken to be considerably larger than the thickness, h, of the plate. Results are presented to illustrate the effects of the plate edges and closely spaced bonds on the bond strength predictions.
RkJQdWJsaXNoZXIy MjM0NDE=