Advantages of a 3-parameter reduced constitutive model for the measurement of polymers elastic modulus using tensile tests

• Published in: Mechanics of time-dependent materials Vol. 20; no. 4; pp. 553 - 577
• Main Authors: Blaise, A., André, S., Delobelle, P., Meshaka, Y., Cunat, C.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.11.2016; Springer Nature B.V; Society for Experimental Mechanics
• Subjects: Characterization and Evaluation of Materials; Classical Mechanics; Engineering; Mechanics; Mechanics of materials; Nanoindentation; Physics; Polymer Sciences; Solid Mechanics; Tensile tests; Elastic modulus; Parameter estimation; Semi-crystalline polymer; Tensile test; Inverse identification; parameter estimation; tensile test; semi-crystalline polymer; elastic modulus; inverse identification
• ISSN: 1385-2000; 1573-2738
• DOI: 10.1007/s11043-016-9312-1

Exact measurements of the rheological parameters of time-dependent materials are crucial to improve our understanding of their intimate relation to the internal bulk microstructure. Concerning solid polymers and the apparently simple determination of Young’s modulus in tensile tests, international standards rely on basic protocols that are known to lead to erroneous values. This paper describes an approach allowing a correct measurement of the instantaneous elastic modulus of polymers by a tensile test. It is based on the use of an appropriate reduced model to describe the behavior of the material up to great strains, together with well-established principles of parameter estimation in engineering science. These principles are objective tools that are used to determine which parameters of a model can be correctly identified according to the informational content of a given data set. The assessment of the methodology and of the measurements is accomplished by comparing the results with those obtained from two other physical experiments, probing the material response at small temporal and length scales, namely, ultrasound measurements with excitation at 5 MHz and modulated nanoindentation tests over a few nanometers of amplitude.