Modification to Heywood's Equations to Estimate the Stress Concentration Factors for Unidirectional Glass Epoxy Laminates with Circular and Square Holes

In this work considering the glass/epoxy laminate as a unidirectional long fiber composite and an orthotropic plate, its average stress, maximum stress, and stress concentration factor have been obtained around a circular hole using ABAQUS and then the result of this part have been verified by Heywood's constitutive equations. In the next step, we considered the stress concentration factor of the orthotropic laminate around a square hole, as a function of different variables: the dimension of the hole, width of plate, orthotropic elastic coefficients, fiber orientation angle, the stress concentration factor for a plate with infinite width, and a magnification factor. Then same procedure was utilized to obtain a formula such as the Heywood formulation which estimates the stress concentration factor of glass/epoxy laminate around square holes. After obtaining this formula, to investigate its accuracy again, ABAQUS software was used to extract the stress concentration factor for different materials such as steel, aluminum, e-glass/epoxy, and s-glass/epoxy. These results were then compared to the obtained formula. The statistics data showed a 10 percent difference between the stress concentration factor around the square hole using ABAQUS and the obtained formula. It can be concluded that, in this special case, instead of using ABAQUS, it's better to use the formula to estimate the stress concentration factor because it saves calculation time. Additionally, for this kind of Glass/epoxy laminate, two smaller holes have been designed around the larger hole to show the deduction of the stress concentration factor.