GEOMETRY AND LOADING EFFECTS ON THE COMPRESSIVE STRENGTH OF FIBROUS COMPOSITES

This work addresses the important engineering problem of the compressi ve strength of fibrous laminated composites, bridging the micromechani cs relevant to compressive failure due to fiber kinking with the globa l characteristics of a composite structure. Simple modeling incorporat es the influence of boundary conditions, laminate thickness and layup configuration. as well as the importance of the microgeometry. The mec hanism of failure under compression is assumed to be microbuckling of fibers that localizes at points with the maximum initial imperfection and leads to the formation and, under critical conditions, propagation of kink bands. To analyze the mechanics of kinking and to calculate t he critical compressive stress. a steady state kink propagation model is utilized for the layers under compression. in the fiber direction. The analysis results are used to gain a better understanding of the in fluence of the macrogeometry (laminate thickness and gauge length) in addition to the microgeometry (fiber diameter and fiber volume fractio n), and the fiber and matrix material properties. The predictions of t he model are compared with experimental results for carbon/thermoplast ic unidirectional laminates under direct compression and cross-ply lam inates under four-point bending.