Image processing assisted stress estimation method for ring compression tests of polymer composite pipes at large displacements

Abstract

A novel method for estimating the fracture stress of ring specimens cut from polymer composite pipes is presented. The method applies image processing for determining the large displacements of the specimen. For image processing, photographs of the deformed specimen were taken before fracture, and a Fourier polynomial was fitted to the points of the digitalized cross section of the ring specimen. The presented mechanical model is based on the captured deformed shape, and it considers the geometrical nonlinearities of the problem. For stress calculation from bending moments, the Navier formula was selected. It was found that the developed method is capable of estimating the stress at break of polymer composite specimens under ring compression.