Cure-induced stress build-up in adhesives: model building and parameter studies

ABSTRACT Prediction of stresses in adhesively bonded joints requires high effort in determination of relevant material properties, which change during cure. In addition, the computational effort using complex viscoelastic finite element (FE) models impends efficient prediction of stress build-up. Rotational and oscillatory rheometry can help to reduce the experimental effort by measuring of modulus of elasticity (MoE) and axial shrinkage along curing. In this publication, shrinkage, development of MoE and Poisson’s ratio of a curing adhesive were numerically modelled between two parallel rheometer plates in order to calculate cure-induced stresses using finite element analysis (FEA). To identify effects of different material properties on stress distribution, a parameter study was carried out and the reciprocal influence of the varied parameters was investigated. Consequently, resulting stresses within the adhesive layer and occurring deformations were investigated with respect to curing time as well as their location. The results showed that final shrinkage and MoE need to be considered not only in final values but also in terms of course of shrinkage and reaction. Stress build-up led to deformation of the rheometer plates, which has to be considered when using rheometry for determination of cure shrinkage.