Stress state around cracks on the boundary of a hole in a photoelastic orthotropic plate under creep

Abstract

The stress-strain state near cracks on the boundary of a circular hole in a linear elastic orthotropic composite plate under tension is analyzed. The distribution of stress intensity factors (SIFs) at the crack tip is found from photoelectric measurements. The dependence of the SIFs on the ratio of crack length to hole radius and on the mechanical properties of the material is established Keywords: photoelasticity, orthotropic composite plate, circular hole with two edge cracks, tension, stress intensity factor Introduction.Theoretical and experimental studies of the stress distribution in composite structural members (plates and shells with stress concentrators (holes, cracks)) are addressed in [1, 3, 6, 7, 11-16, etc.)].To determine the stress intensity factors (SIFs) around cracks propagating from the edges of a hole in elastic isotropic plates, use is made of numerical [1, 3], theoretical-and-experimental [2], and experimental [8] methods. The major results in the field have been obtained in the static case. Solutions to dynamic problems for anisotropic bodies with stress concentrators obtained by the photoelastic method can be found in [12][13][14][15].We will use photoelastic measurements to study the stress distribution around cracks on the boundary of a hole in linear elastic fiber-reinforced composite plates under a tensile force normal to the cracks. Use will be made of a procedure that produces more accurate results than in [16]. The mathematical model discussed below allows us to increase the neighborhood around the crack tip to improve the accuracy of determining the fringe orders and, hence, the SIFs.1. Problem Formulation. Procedure of Analysis. To describe the mechanical and optical behavior of the composite, we will assume that it is homogeneous and anisotropic. Consider a photoelastic plate under creep.The orthotropic plate is weakened by a crack on an interval ( ) 2l of the x-axis aligned with the principal axis of orthotropy of the material (Fig. 1). The plate is subject to a tensile force P = const applied far from the stress concentrator. In the case of plane stress state, the components of the stress tensor s s t