Read, B E; Dean, G D; Wright, L (2000) A proposed model for the non-linear stress/strain behaviour of rubber-toughened plastics. NPL Report. CMMT(A)301

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Abstract

An elastic-plastic model has been developed for describing the non-linear, stress/strain curves of rubber-toughened plastics. Following a linear elastic response at low strains, it is assumed that the material undergoes plastic deformation which, for dilatational stress states, is enhanced by the generation and growth of cavities within the rubber particles. The model is based on Gurson's theory of plasticity in porous materials and follows the developments proposed by Bucknall and coworkers. Parameters are included that allow for the effect of pressure on the yield stress of matrix material between the cavities and for the influence of void interactions on matrix shear banding. Account is also taken of the change in matrix composition, and hence the matrix yield stress, during void nucleation. The nucleation is assumed to occur over a critical range of volumetric strain Bv and to involve the replacement of rubber particles by an equal volume of effective cavities. Twol different nucleation functions have been investigated to describe the dependence of the effective void fraction on Ev
General relations are presented that govern the elastic, yield and flow behaviour under multi axial stress states. Derived equations are also given in an Appendix for uniaxial compression, shear, uniaxial tension and butt-joint tension respectiv~ly. These equations were used in detemrining required material parameters and subsequently predicting the behaviour in compression, tension and butt-tension from shear hardening data. The predicted and observed behaviour show quite good agreement, indicating that the model may be applied with some confidence to the multiaxial stress states in finite element calculations.

Item Type:	Report/Guide (NPL Report)
NPL Report No.:	CMMT(A)301
Subjects:	Advanced Materials Advanced Materials > Polymers
Last Modified:	02 Feb 2018 13:17
URI:	http://eprintspublications.npl.co.uk/id/eprint/1927

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