Abstract
Finite element mesh of multi-directional 4D carbon/carbon (C/C) composite was reconstructed from 2D images obtained by X-ray tomography. Thus, imperfections in the composite such as voids, misalignment and cross-section distortion of the fibre bundles were directly incorporated in the finite element mesh. 2D images of the composite were also used for the characterization of the porosity in the composite. The effect of these micro structural imperfections was studies by assuming perfect bonding at the bundle/matrix interface. The initial mechanical properties of the composite were obtained from unit cell analysis using asymptotic homogenization and moduli in x, y and z directions were 39, 25 and 44 GPa. However, matrix and bundle/matrix interfacial cracks were also clearly visible in the X-ray tomographic images. Later, the effects of debonding was incorporated by using frictional cohesive interaction at bundle/matrix interfaces and matrix cracking was modeled by degrading the elastic properties of matrix. Final, the response of the composite was studied under six individual load cases.
Highlights
The multi-directionally reinforced carbon/carbon (C/C) composites are extensively used in aerospace industry due to their high performance mechanical properties
The volume average of the properties of unit cells were considered as the effective homogenized properties (EHP) for the composite and are given in Table 3 with associated standard deviation (SD)
Sharma et al /Finite Element Analysis for Mechanical Characterization of 4D Inplane Carbon/Carbon Composite with Imperfect Microstructure 177 Table 3 Mechanical properties of the composite (Here E and G are in GPa)
Summary
The multi-directionally reinforced carbon/carbon (C/C) composites are extensively used in aerospace industry due to their high performance mechanical properties. Damage in the form of matrix cracking, debonding of fiber/matrix and fiber bundle/matrix interfaces occurring during manufacturing, affects the properties adversely (Sharma (2012), Rao (2008)ab) These imperfections in the composite were broadly divided into two categories, local and global imperfections. Sharma et al /Finite Element Analysis for Mechanical Characterization of 4D Inplane Carbon/Carbon Composite with Imperfect Microstructure 171 are the dominating defects in the composite Some of these imperfections can be considered directly in the analysis by obtaining the finite element (FE) mesh from X-ray tomographic images. Sharma et al (2010) studied the effect of the variation in the microstructure of 3D C/C composite on the mechanical properties by reconstructing FE mesh form X-ray tomographic images. The results were compared to the experimental data available in literature
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