A novel approach to assessing yarn/matrix (or yarn/yarn) in situ interfacial strength in 3D woven composites

A novel in situ experimental-numerical approach combining the meso-scale Digital Image Correlation (DIC) and a cohesive zone model (CZM) is proposed to assess the in situ interfacial strength of 3D woven composites. In order to obtain a specimen with interface damage as the dominant damage mode and simple internal structure, the specimen is particularly designed and cut into a dog-bone thin slice, which contains an in situ typical form of yarn/yarn or yarn/matrix interfacial structure. Benefiting from the simple internal structure of the specimen, the geometry of the numerical simulation model can be established quickly based on the micrographs of the specimen. A cohesive zone model is used to evaluate the debonding behavior of interface between yarn/yarn or yarn/matrix. With meso-scale DIC, tensile experiments are carried out on the particularly designed specimens. All specimens are broken at the yarn/yarn or yarn/matrix interface. Local strains obtained by meso-DIC show a consistent trend with that predicted by simulation, which proves the accuracy of the simulation model. The effects of interfacial parameters on the simulated strength are discussed. Through the combination of experiment and simulation results, the range of interfacial normal strength can be estimated.