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Mechanical properties of transversely isotropic fibre network composites

Lin, Xiude 2018. Mechanical properties of transversely isotropic fibre network composites. PhD Thesis, Cardiff University.
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Fibre reinforced composites have been widely applied to many fields for their extraordinary mechanical and other physical properties such as thermal and electric conduction etc. The structure of the composites can be crucial to the overall mechanical properties of the composites. The designed fibre-network composite in this research is inspired by fibrous materials with overlap, such as metal fibre sintered sheet (MFSS). With a fibre network instead of uncontacted fibres as the reinforcement, the composite is expected to produce enhanced mechanical properties. Based on the designed transversely isotropic fibre-network composite, the elastic, elastoplastic and viscoelastic properties of the composite have been investigated by the Finite Element Method (FEM) to better understand the mechanical properties of the fibre-network composite. The in-plane stiffness has illustrated a much larger value than the out-of-plane stiffness for this designed fibre-network structure. Furthermore, the normalised in-plane stiffness has revealed a linear relationship with volume fraction, whereas the normalised out-of-plane stiffness has demonstrated a polynomial relationship with volume fraction when the volume fraction is not too large. The in-plane and out-of-plane yield surfaces, under biaxial stress states, indicate that the yield strengths meet the Hill yield criterion. The transversely isotropic fibre network composite structure exhibits a larger out-of-plane yield strength than the in-plane yield strength, although the out-of-plane stiffness is smaller than the in-plane stiffness, which is expected to be related to the matrix properties. An analytical model has been proposed and have successfully modelled the elastoplastic stress-strain III response of the simplified RVE. In terms of the viscoelasticity of the fibre-network structure, the collagen aerogel indicates a linear relationship with relative density for the in-plane relaxation modulus, while a cubic polynomial relation with relative density for the out-of-plane relaxation modulus. For the collagen hydrogel, it illustrates a larger in-plane strain than the out-of-plane strain under constant stress. When a constant tensile strain is applied, both the in-plane and out-of-plane relaxation moduli exhibit a nearly proportional relation with volume fraction.

Item Type: Thesis (PhD)
Date Type: Submission
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: Fibre Network; Composites; Transversely isotropic; Mechanical properties; Cross-linker.
Funders: China Scholarship Council, Cardiff University School of Engineering
Date of First Compliant Deposit: 1 November 2018
Last Modified: 14 Apr 2021 15:11

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