The use of the J-integral vector to analyse adhesive bonds with and without a crack

The singularity problem in adhesive joints is mentioned in finite element analyses but it is often ignored. Adhesive joints may have cracks and certainly many sources of singularities due to the adherend corners. Cracks are easily dealt with using fracture mechanics concepts. However, angular wedged notches or bi-material wedges are more difficult to treat because the strength of the singularity must be known. Another point that must be born in mind is the fact that crack propagation in adhesive joints occurs in a mixed mode, especially for ductile materials. The present study shows that the use of the J-integral can treat most of the above problems. A very useful fracture mechanics method using the J-integral vector approach is discussed in connection with adhesive bonds but can be generalized to other singular problems. It is shown that the J vector can be used in adhesive bonds where there is always discontinuity in material properties regardless of whether there is a crack or not. One of the advantages of using the J vector in numerical analyses for homogeneous materials is that the accurate stresses (better known) and displacements in the far field can be used to calculate J instead of the not-so-accurate values near the singular point. A method for dealing with the singularity in adhesive bonds, which can be used in engineering design and analysis, has been established in this investigation.