Speaker
Description
In mechanical engineering, aerospace engineering, and civil engineering there are many situations where multilayer structures are applied. This can, for instance, be the overlap region of an adhesive joint, a local patch reinforcement on a substrate, or a substrate with a protective layer. Under given mechanical or thermal loading due to the dissimilar material properties typically stress concentrations will arise at the ends of the involved layers which might lead to the onset of debonding cracks and a subsequent debonding failure.
In order to assess such situations in the framework of linear elasticity theory a closed-form analytical approach is suggested based on layerwise displacement representations that take into account singular stress concentrations. From this by means of the principle of minimum potential energy an approximate closed-form description of the resultant deformation and stress distribution can be derived and validated by accompanying finite element calculations.
In order to assess potential failure in the framework of finite fracture mechanics debonding cracks of finite length are introduced and the corresponding incremental energy release is identified. Using the hybrid failure criterion suggested by Leguillon [1] then it can be clearly concluded whether such debonding failure will happen in reality or not. By a corresponding optimization problem also the minimal critical loading leading to failure can be determined. This is of high significance for the practical application.
References:
[1] Dominique Leguillon: Strength or toughness? A criterion for crack onset at a notch. European Journal of Mechanics – A/Solids 21 (2002) 61-72.
