Discrete Element Simulation of Transverse Cracking During the Pyrolysis of Carbon Fibre Reinforced Plastics to Carbon/Carbon Composites

摘要

The fracture behavior of fiber-ceramics like C/C-SiC strongly depends on theinitial damage arising during the production process. We study the transversecracking of the 90{\deg} ply in [0/90]S cross-ply laminates due to thethermochemical degradation of the matrix material during the carbonizationprocess by means of a discrete element method. The crack morphology stronglydepends on the fiber-matrix interface properties, the transverse ply thicknessas well as on the carbonization process itself. To model the 90{\deg} ply atwo-dimensional triangular lattice of springs is constructed where nodes of thelattice represent fibers. Springs with random breaking thresholds model thedisordered matrix material and interfaces. The spring-lattice is coupled byinterface springs to two rigid bars which capture the two 0{\deg} plies oradjacent sublaminates in the model. Molecular dynamics simulation is used tofollow the time evolution of the model system. It was found that under gradualheating of the specimen, after some distributed cracking, segmentation cracksoccur in the 90{\deg} ply which then develop into a saturated state where theply cannot support additional load. The dependence of the micro-structure ofdamage on the ply thickness and on the disorder in spring properties is alsostudied. Crack density and porosity of the system are monitored as a functionof the temperature and compared to an analytic approach and experiments.