Brittle fracture of adhesive joints

Abstract

The effect of mode mix upon crack path is examined for a brittle epoxy adhesive. The mode mix is varied over wide limits by using asymmetrical double cantilever beam and Brazil nut specimen configurations. The observed crack paths are interracial, in-layer, and alternating from one interface to the other in a periodic fashion. The probability of occurrence and toughness of each crack path is measured, and is compared with existing theory. Interfacial fracture is the most common path for all values of mode mix; the interfacial toughness increases dramatically with increasing mode II component of remote load. Under remote mode I loading the alternating crack path covers approximately 20 percent of the fracture surface of the specimens and has the highest macroscopic toughness. The effect of residual stress magnitude, layer thickness and mode mix upon the wavelength of the alternating crack mode is measured. Predictions based on a previous analysis by Akisanya and Fleck [1] compare favourably with the measured values.

Fracture initiation in bi-material joints subject to combined tension and shear loading

“…7). The observed failure mechanism is consistent with previous work on crack path selection in adhesive joints; increasing magnitude of remote shear results in interfacial crack growth [31].…”

Reliability Aspects of Microsystems for Automotive Applications

“…The observed phenomenon is very similar to the findings of Akisanya and Fleck, who classify their failure modes into four categories: alternating crack, in-layer failure, interfacial failure, serrated interfacial failure. [8] R. Müller-Fiedler et al/Reliability Aspects of Microsystems for Automotive For pure mode I loading (symmetric sample, 675/675 mm), the crack is permanently changing between the two interfaces, caused by the intrinsic tensile stresses in the bonding layer. [9] A closer look at the fracture pattern reveals that the crack actually does not reach the interface to the silicon but rather propagates in the plane of the lead precipitations.…”

Influence of copper layer on epoxy acrylate based solder mask surface chemistry and the effect on epoxy adhesion

“…Akisanya et al [24] reported a higher bonded joint toughness if the failure mode exhibits a serrated crack path compared to a flat crack path at the interface of two components. In terms of the crack path within the base material, the crack has to follow the structure of the glass fiber mat resulting in a longer crack path.…”