Compression-induced axial crack propagation in DCDC polymer samples: experiments and modeling

Abstract

The fracture strength of PMMA is studied using columns with rectangular cross- section that contain a central hole and are subjected to axial compression. Samples with geometries such that the width is 2, 3, 4, and 5 times the diameter of the hole are investigated. Cracks are initiated by introducing sharp notches in the axial direction at the crowns of the hole in each sample. The sample is then subjected to axial compression such that the axial cracks grow in a stable manner until a critical compression is attained, after which the cracks extend rapidly in the sample but do not reach its ends. To predict the experimental results, we have first sought to use several published models, but discovered that none would produce results in accord with our data, as they seem not to address the essential features of our beam-column experiments. We have then developed a simple model that consists of a suitably modified version of an elasticity solution based on a short-crack in an infinite plate, combined with a beam-column solution for a long-crack. This model yields results in good accord with our data and also gives reasonable values for the fracture toughness of the material. A comparative discussion of several published models is presented at the end of the paper, pointing out that linear elasticity is not an appropriate tool for solving the present beam-column problem.