Free-edge singularities meet the microstructure: Important considerations

The significance of the free-edge singularities in angle-ply laminates and due to fiber terminations is explored and results are compared to that of a singularity due to the presence of a crack in the same region. A new dimensionless ratio, Δ is defined to compare the intensity of the singularities and the ratio shows that the stress field due to a crack of finite size is approximately twice that generated by free-edge singularities and 1.5 times as intense as the field generated by fiber terminations. For a range of material properties studied, it was found that the free-edge singularity was shown to effectively disappear as the ply angles decrease below ±15° or increase above ±85° and the fiber termination singularity was surprisingly insensitive to material properties. The results of this study suggest that singularities due to cracks dominate the stress field in the free-edge as compared to singularities at lamina discontinuities in equivalent media and fiber terminations.