Compressive Failure Prediction From Nonlinear Finite Element Analysis of A Notched 0 Degree Composite Specimen

The strength of unidirectional composites is often lower in compression than in tension, making compressive strength an especially important design criterion. The compressive strength is sensitive to the presence of notches and stress gradients. Finite element analysis was used to determine the strain gradient at a shallow circular notch in one edge of a 0 degree carbon/epoxy composite specimen, and to predict failure due to a localized buckling instability. The specimen was first analyzed with a "global" model of the full specimen, and displacements along a curve near the notch were stored and used as boundary conditions for a more detailed "submodel" in the immediate vicinity of the notch. At the onset of instability, a displaced plot of the finite element model shows oscillations in the transverse direction along the arc of the notch, just off the centerline, which is essentially at the same location where failure initiated in the test specimens. Results are compared with experimental values for failure stress and notch strain concentration for a range of loading rates and test temperatures.