Julien Jumel

Antagonist adhesion effects due to variable substrate surface

The effects of variability of intrinsic adhesion within a joint have been studied using a single cantilever beam (SCB) test. Fracture energy was found not to be a simple function of relative areas of 2 surface pre-treatments: a ‘weak’ zone decreased strength more than expected from simple, additive considerations. By severing the adhesive along the strong–weak transition, fracture energy increased. The prior antagonist effect appears to be directly linked to supplementary stresses generated near the crossover by continuity of the adhesive layer, existent despite differences in adhesion.

Comparison of Cyclic and Monotonic Loading of a Double Cantilever Beam Adhesion Test

Double Cantilever Beam (DCB) specimens were made from aluminium plates bonded with Hysol®EA9321 epoxy adhesive. These were tested both under monotonic and cyclic loading conditions. Experimental testing data were obtained from classic force and displacement measurements, as well as from backface strain recordings. Apart from the usual crack propagation monitoring, evolution of the process zone at the crack tip was studied during the experiment. Results of fatigue were compared with those of standard loading. Despite the viscoelastic nature of the adhesive, an elastic treatment of the results proved most satisfactory. In addition, good agreement was found between experimental and theoretical results obtained with a Timoshenko beam on Winkler elastic foundation model.

Inverse End Loaded Split test configuration for stable mode II crack propagation in bonded joint: macroscopic analysis—effective crack length approach

Mode II crack propagation along a bonded joint is investigated using newly proposed Inverse-End Loaded Split experimental configurations. This test configuration allows stable crack propagation all along the crack propagation path. The specimen compliance and strain energy release rate for the new experimental arrangement are derived. An experimental data reduction procedure, based on the effective crack length approach, is also proposed. Two series of experiments are performed to assess the stable nature of the crack propagation and data reduction scheme associated to this new experimental arrangement. In addition to stable crack growth, the experiment may prove his worthiness in the study of crack onset under mode II loading.

COHESIVE ZONE MODEL IDENTIFICATION WITH DCB TEST PARAMETER ESTIMATION SENSITIVITY

Crack initiation and propagation conditions during a double cantilever beam test under constant rate loading are investigated. Elastic-plastic cohesive zone model is considered to represent the interface separation law. A finite difference model is derived to evaluate the applied force versus specimen opening evolution. Cohesive zone model parameters effect on energy release rate is investigated to evaluate the ability of measuring protocol based on J-integral approach for cohesive zone model identification. Confidence intervals of these estimated parameters are evaluated rigorously considering reasonable assumption on numerical simulation conditions regarding experimental one, with nonlinear optimization algorithm.