Read, B E; Dean, G D; Wright, L* (2001) Effects of cavity growth and orientation hardening on the stress.strain behaviour of rubber-toughened plastics. NPL Report. MATC(A)35

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Abstract

Details are presented of extensions to an elastic-plastic model for the non-linear stress/strain behaviour of rubber-toughened plastics. Consideration has been given to the effects of a matrix expansion during plastic deformation on the growth of cavities formed in the rubber particles under dilatational stress fields. The predicted matrix expansion relates to the pressure dependence of the yield stress for the uncavitated material. When this effect is included in the model, good agreement is obtained between the calculated and observed tensile stress/strain behaviour of an acrylonitrile-butadiene-styrene (ABS) plastic. The gradual increase in stress with strain in the post-yield region up to failure has also been This strain hardening is ascribed to molecular orientation which produces an considered. entropy elastic stress contribution that increases with plastic strain. Using relations from the kinetic theory of rubber elasticity, the orientation hardening is characterised by a modulus GR For ABS the calculated values of GR (~5.5 MPa) from tensile and shear data are somewhat lower than values obtained for untoughened glassy plastics, but consistent with the extension of highly entangled polymer chains in the poly(styrene-acrylonitrile) matrix. Further work is proposed to (a) explore the validity of the predicted expansion during plastic deformation for stress states that do not produce cavitation (b) investigate a possible stress-induced structural deageing during yield and (c) incorporate the effects of orientation hardening into the model for the general case of multiaxial loading.

Item Type:	Report/Guide (NPL Report)
NPL Report No.:	MATC(A)35
Subjects:	Advanced Materials Advanced Materials > Polymers
Last Modified:	02 Feb 2018 13:17
URI:	http://eprintspublications.npl.co.uk/id/eprint/2029

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