Uniaxial compression testing of polymeric materials

• Published in: Polymer testing Vol. 29; no. 3; pp. 302 - 309
• Main Authors: Jerabek, M., Major, Z., Lang, R.W.
• Format: Journal Article
• Language: English
• Published: Kindlington Elsevier Ltd 01.05.2010; Elsevier
• Subjects: Applied sciences; Compression tests; Cone compression test; Exact sciences and technology; Friction; Mathematical models; Mechanical properties; Modulus of elasticity; Physical properties; Poisson's ratio; Polymer industry, paints, wood; Polypropylene; Polypropylenes; Post-yield behavior; Properties and testing; Strain; Strain hardening; Strain softening; Technology of polymers; Testing and control; True stress; Uniaxial compression test; Uniaxial compression test; Strain softening; Polypropylene; Cone compression test; Post-yield behavior; Poisson's ratio; Strain hardening; Mechanical measurement; Stress strain relation; Propylene polymer; Mechanical properties; Compressive strength; Experimental study; Compression test; Poisson ratio; Uniaxial stress; Olefin polymer
• ISSN: 0142-9418; 1873-2348
• DOI: 10.1016/j.polymertesting.2009.12.003

Two methods for uniaxial compression testing were investigated and compared using polypropylene as a model material. An overview of various parameters affecting compression test results is provided with particular emphasis on friction between the specimen and the compression plate. A procedure for the determination of the compressive modulus is introduced and results are shown. To enable the detection of instability associated with friction and barreling and to calculate true stress-true strain curves, the measurement of transverse expansion of the specimen at large strains is necessary. Nominal and true Poisson's ratio values in the pre- and post-yield regime are presented and the resulting true stress-true strain curves are compared and discussed. While in the post-yield regime nominal stress values misleadingly result in strain hardening, significant strain softening was observed using true stress values representing the intrinsic material behavior.