Effect of heterogeneity at the fiber/matrix scale on predicted free-edge stresses for a [0/90]S laminated composite
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2017 International Committee on Composite Materials. All rights reserved. The effect of the free-edge on the interlaminar stresses that develop in a [0/90]s laminated composite under uniaxial tension was explored while directly modeling the microstructure. A random arrangement of fibers was generated for each ply, and a large section of the laminate was modeled. The discrete case, where the fibers and matrix were directly modeled, was compared to the homogenous model, where plies were treated as homogeneous, transversely isotropic materials. The deformed cross-sections were compared for the two cases, showing that the discrete case exhibited local perturbations due to the heterogeneous microstructure. However, there was also a difference at a larger scale of up to 11% between the cases, indicating that the effective properties from a periodic analysis may be misrepresentative of the finite domain considered in this paper. The normal stresses along the ply interface were compared, showing great differences. The discrete case exhibited a complex pattern of stresses that depended on the fiber locations near the ply interface and the effect of the free-edge. In contrast, the homogeneous case predicted zero interlaminar normal stresses away from the free-edge and a stress singularity at the intersection of the free-edge and the ply interface. The effect of the fibers, which occurs without a free-edge present, and the free-edge effect were separated, showing that the fibers significantly affect the interlaminar normal stresses. Once isolated, the stresses that develop due to the free-edge effect matched well between the two cases, except very close to the free-edge, since the discrete case does not have a singularity on the ply interface. This initial study into the effect the heterogeneous microstructure on interlaminar stresses near a free-edge showed the importance of considering the discrete fibers near the interface if the interlaminar stresses are to be accurately predicted.
