FINITE ELEMENT ANALYSIS FOR MECHANICAL CHARACTERIZATION OF 4D INPLANE CARBON/CARBON COMPOSITE WITH IMPERFECT MICROSTRUCTURE

Abstract

FINITE ELEMENT MESH OF MULTI-DIRECTIONAL 4D C/C COMPOSITE WAS RECONSTRUCTED FROM 2D IMAGES OBTAINED BY X-RAY TOMOGRAPHY. THUS, THE IMPERFECTIONS IN THE COMPOSITE VOIDS, MISALIGNMENT AND CROSS-SECTION DISTORTION OF THE FIBRE BUNDLES WERE DIRECTLY INCORPORATED IN THE FINITE ELEMENT MESH. THE 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 INTERFACE 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 INCLUDED BY DEGRADING THE ELASTIC PROPERTIES OF MATRIX. FINAL, THE RESPONSE OF THE COMPOSITE WAS STUDIED UNDER SIX INDIVIDUAL LOAD CASES.