Stress concentrations and failure criteria for orthotropic and anisotropic plates with circular openings

Theoretical solutions and results are given for stress concentrations and failure stresses in orthotropic and anisotropic composite plates. Solutions for the stresses around the opening are given for plates subjected to uniaxial, biaxial, and shear loading. The types of composites for which equations are given for stress concentration factors include unidirectional laminates, unidirectional laminates with oriented fibers, bidirectional balanced laminates, and multilayered laminates. A failure criterion based on modified Hencky-Von Mises distortion energy theory is also presented for predicting (1) the externally applied load which will initiate failure at the opening and (2) the location of the failure. The strength of composite plates with cutouts is less sensitive to stress concentrations than the strength of plates made of isotropic materials. Typical numerical results are presented for stress concentrations and strength of fiberglass/epoxy, boron/epoxy, and graphite/epoxy plates with cutouts. A test-theory comparison is also shown for stress concentrations in fiberglass plate containing circular opening and subjected to uniaxial tensile loading.