Deformation Behaviour of Woven Fibre Elastomeric Composites

Milad, Mohamed Mousa Moraga and Green, Sarah and Ye, Jianqiao and Lambert, Colin (2022) Deformation Behaviour of Woven Fibre Elastomeric Composites. PhD thesis, Lancaster University.

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Abstract

The focus of this thesis is both to improve the characterisation of hyperelastic materials and to develop a simple hyperelastic constitutive model for different composites materials, including woven fabric reinforcements with a hyperelastic matrix. Physical tests are performed on PVC/nitrile elastomer with woven continuous nylon reinforcement composite sheet under loading under uniaxial extension, pure shear, picture frame and bulge tests achieved via wide strip tension testing. Through the novel use of an advanced non-contact optical strain measurement technique, the hyperelastic material behaviour of the composite is investigated, and materials parameters reported for both the warp and the weft directions of reinforcement fibre alignment. To characterise the materials, an appropriate constitutive model is determined by fitting experimental shear and uniaxial tension data. The non-contact technique is used to acquire normal and shear strains at the surface of the composite sheet material when loaded to tensile strains (stretches). Directly measured shear strains are compared to those derived from the normal strain outputs of an optical rectangular strain rosette array, where the two measures are in close agreement. The measured mechanical behaviour under loading is used to determine an approximate strain energy function for the composite via ABAQUS software hyperelastic materials modelling curve fitting, with the Ogden and Yeoh hyperelastic models showing reasonable agreement to experimental data. A simple hyperelastic constitutive model is developed to investigate nonlinear mechanical properties of composites (loaded to large deformations) made of an elastomeric matrix containing biased woven fabric reinforcement. The strain energy function of the developed constitutive model is decomposed into four parts via a series of strain energy contributions. These include the strain energy from the matrix, the tensile energy from fibre elongation in the warp and weft directions and the shearing energy from the interaction between the warp and weft yarns. Furthermore, a new method is proposed to calculate shear strain whereby measurements are taken directly from the surface of the iv sample. The three-dimensional digital image correlation (3D-DIC) technique is shown to be a useful tool for obtaining the membrane stress and strain fields during the bulge test. The 3D video gauging, combined with DIC, captures three-dimensional surface geometry and deformed surface displacements.