Dean, G D; Mera, R D (2004) Determination of material properties and parameters required for the simulation of impact performance of plastics using finite element analysis. NPL Report. DEPC-MPR 007

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Abstract

Measurement methods are briefly described for determining true stress/true strain curves for ductile plastics under tension, shear and compression. Measurements have been made on a talc filled, rubber-toughened propylene-ethylene copolymer used for the manufacture of motor vehicle interior door trim. Results are analysed to determine the properties and parameters required by selected elastic-plastic models for the simulation of impact performance using finite element methods. For this purpose, measurements under tension are required out to large strains and over a wide range of strain rate which includes very high rates (~ 1000 s-1) associated with impact events. Measurements at large strains are achieved using a non-standard test specimen shape. The determination of properties at high strain rates is achieved by modelling measurements at low and moderate strain rates and calculating the behaviour at high strain rates by extrapolation.
Measurements of stress/strain curves under tension, shear and compression and of Poisson’s ratio with strain are used to derive parameters for the von Mises and linear Drucker-Prager models and for a new model that takes account of the influence of cavitation on plastic deformation. Limitations in the applicability of the first two models for describing the deformation behaviour of the copolymer are demonstrated. The results of measurements made on injection moulded specimens of the copolymer and specimens cut from a component moulding are compared.
The implications of differences in these results on the determination of model parameters are discussed.

Item Type:	Report/Guide (NPL Report)
NPL Report No.:	DEPC-MPR 007
Keywords:	elastic-plastic models, rate-dependent plasticity, linear viscelasticity
Subjects:	Advanced Materials Advanced Materials > Composites Advanced Materials > Materials Modelling
Last Modified:	02 Feb 2018 13:16
URI:	http://eprintspublications.npl.co.uk/id/eprint/3054

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