Homogenization Studies of Carbon/Epoxy Composites

Carbon fiber reinforced polymer (CFRP) composite has applications in various fields like aerospace, automotive, civil, marine etc. The composite has a high strength to weight ratio and stiffness to weight ratio. In this paper, a six layered plain weave carbon fiber reinforced epoxy polymer composite which differs in geometry from the stacking of a 0-90 oriented unidirectional laminate composite is tested to determine the in-plane effective elastic mechanical properties like Young’s moduli, Poisson’s ratio and shear modulus. These properties are obtained by homogenization by using a commercially available finite element package, ABAQUS. Homogenization is required so that the effective properties may be used in the design and analysis of large scale load bearing composite structures. Tests were performed to determine the in-plane material properties of the laminate as per ASTM standards. The standards used are ASTM E132-17 (Polymer Poisson’s ratio)1, ASTM D3039M – 17 (Tensile properties of composites)2, ASTM D3518M – 13 (In-plane shear properties)3. Different techniques like Digital image correlation (DIC) and strain gage measurements are used to establish a relation between the material displacement and the load. The effective properties are found out from a finite element mesoscopic analysis of the complex meso-structure geometry of the composite model based on the volume fractions of the fiber and the matrix in the composite. The dimensions for the geometrical model are assumed from the SEM images of the laminates cross-section and defined as sinusoidal waves in terms of yarn width, thickness and spacing. The homogenized properties are found out using the principle of superposition. For mesh convergence study, the principle of superposition is used which is computationally efficient compared to a 3D FEA model. The experimental results confirm the validity of the numerical results.