Development of Control Setup for a Material Testing Machine and Experimental Analysis of the Effect of Void Volume Fraction on the Strength of Recycled High-Density Polyethylene Material

Abstract

This study is part of a larger research effort to investigate the mechanical response of composite beams to cyclic loading caused by waves striking beams imbedded in a low-cost sea wall. In the course of the research, it has been determined that material characterization of the beams is needed, and toward this end an MTS (Materials Test Systems) testing machine has been purchased by the TAMU Ocean Engineering Department. The testing machine was used for the purpose of testing recycled high-density polyethylene glass fiber composite specimens in order to characterize the stress-strain response and to measure the effect of void volume fraction (VVF) within the high-density polyethylene beams. Samples taken from different areas of the beams with varying VVF were tested and the effect of these voids was investigated for the purpose of determining the efficacy of deploying these structural components within low-cost sea walls. The study includes developing testing protocols, calibrating, and proof testing the machine in order to perform the experiments. Since the lab’s testing machine does not have a controller, a control setup is developed herein to control the MTS Testing Machine with signal processing via a National Instrument USB-6346 Data Acquisition Device and LabVIEW software. Results display the decrease in the stiffness as the VVF increases as well as decreases in the ultimate stress and ultimate strain. Increasing strain rates displayed higher stiffness, ultimate stress, and ultimate strain values. The results are discussed and invalid tests are described in detail wherein large voids locally misrepresent the general behavior and are incongruent with the valid tests.