Influence of non-uniform fiber arrangement on microscopic stress and failure initiation in thermally and transversely loaded CF/epoxy laminated composites

The influence of spatial fiber distribution on microscopic stress state and therefore the initiation of transverse cracking in CF/epoxy laminated composites is investigated. Models for finite element analysis (FEA) were generated containing 225 fibers in an irregular arrangement. First, the distribution of maximum interfacial stresses in the models containing fibers in an irregular arrangement is compared with those in a regular arrangement. The results show regular models do not represent the actual distribution of maximum interfacial stresses and therefore can not be used in failure analysis. Second, the irregular FE-models are used to calculate the interfacial stresses at the onset of failure observed by an in situ bending experiment in our previous work. The load that caused failure to a micro- and macroscopic scale calculation is applied. The results of the microscopic calculation provide detailed characteristics of the microscopic stress distribution at the onset of failure.