ExpE Properties Polymer Materials rev0

Thestressand strain relationship is therefore

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Unformatted text preview: nd time dependent elastic deformation recovery) under load. The stress and strain relationship is therefore affected by the rate of deformation. Unlike the plastic deformation of metals (via dislocation motion), thermoplastics deform via polymer chair stretching, rotating, sliding and disentangling. You will often see a drop in the stress beyond the yield point and a graduate increase in stress as deformation continues. ExpE Properties Polymer Materials rev0.docx The purposes of this experiment are to first observe the tensile behaviour of two polymer materials under two different strain rates. Upon establishing the tensile stress vs. strain curves, differences between two materials and strain rates are to be compared and discussed. Table 1 Mechanical Properties of Acrylic and Polycarbonate Tensile Strength (psi) % Elongation Elastic Modulus (psi) Density (g/cm3) 12,000 5 450,000 1.22 Polymethyl Methacrylate (PMMA) (Acrylic, Plexiglas) Polycarbonate (PC) 11,000 130 400,000 1.20 Material and Experimental Procedures Two types of polymer material will be used for this experiment. One is a ductile polymer (polycarbonate) and the other is a brittle polymer (acrylic). Large sheets of the material (0.125” thick) will be purchased, cut to smaller size, and mounted onto a machining jig (Figure 1). CNC machine will be used to machine the tensile specimens following the dimensions specified in ASTM D638‐03 Standard Test Method for Tensile Properties of Plastics. Figure 1 CNC machiningjig After machining, the tensile samples are to be lightly sanded to remove surface irregularities. Measure the final sample width, thickness and mark two fine lines defining the gauge length. Two polycarbonate and...
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This document was uploaded on 03/02/2014 for the course ENGINEERIN MAAE 3901 at Carleton CA.

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