Finite element analysis of ply-by-ply and equivalent stress concentrations in composite plates with multiple holes under tensile and shear loading

The finite element method is employed to analyze the stress concentration effects of multiple holes in laminated composite plates. The analysis considers the composites both as homogeneous orthotropic plates producing an equivalent property solution, and as laminates consisting of laminae of various orientations, each having its own stress concentration. Theoretical verification of special cases of the analyses are described. Finite element results for [0/+/- 45/0](2s) and [0/+ 45/90](2s) laminates loaded in tension or shear are presented. The results are condensed into 'design curves' to allow the designer to estimate stress concentrations. These curves allow comparison of stress concentrations on a lamina or laminate basis, for tension or shear, and for the number, size and relative position of holes. It is concluded that the presence of multiple holes tends to increase stress concentration over that which it would be if there were only one hole. Certain sizes and locations of holes also tend to increase stress concentration. (C) 1997 Elsevier Science Ltd.