Strength Prediction of Adhesively Bonded Joints using Plastic Zone Size Criterion

Abstract

The prediction of the strength of adhesively bonded joints has been an issue of considerable interest in literature. This exercise requires numerical techniques combined with experimental programs and matching the two to arrive at a viable criterion. The configurations used for the study are single lap adhesively bonded joints between (i) aluminium (Al) – aluminium (Al) and (ii) carbon fibre reinforced composite (CFRP) and aluminium adherends with Redux-319A epoxy. Geometric and material non-linear finite element analysis was conducted using the NASTRAN software package to establish the proposed plastic zone size (PZS) failure criterion. On the same configuration both experimental program for joint strength and numerical analysis were conducted. The plastic zone size corresponding to failure load was initially estimated from Al-Al joints. The same value was used to predict failure load for CFRP-Al bonded joint. The average experimental value and numerical predictions for CFRP-Al joints matched within 7%. This study suggests an alternative method of strength prediction of adhesively bonded single lap joint in presence of inelastic behaviour of adhesive material.