Curvature effects on compressive failure strength of long fiber composite laminates

A simple model is developed to study the compressive failure strength of woven composite laminates. Two different configurations, a flat plate under in-plane compression and a thin-walled cylindrical tube under external pressure, are considered. Two micromechanisms observed in experiments, delamination of thin layers at the inner surface for the tube and formation of kinking bands for the flat plate, are used to develop the model. An energy criterion is employed to determine the failure strength of cylindrical tube. Three nondimensional parameters, related to interlayer surface energy, initial misalignment of fibers, and the delaminated layer thickness as well as the radius of curvature of the tube, are identified as governing parameters for different failure modes. The model predictions agree well with experimental results.MSS 92 09309 93/0

Numerical simulation of semicrystalline nylon 6: elastic constants of crystalline and amorphous parts

The elastic responses of crystalline and amorphous parts in semi-crystalline nylon 6 are determined by computer simulation using the finite element method. Semi-crystalline nylon 7 is modelled as a composite consisting of alternating layers of lamellar crystals and amorphous regions. Full morphological details identified by Lin and Argon in their highly textured nylon 6 bulk samples are incorporated in the model. An optimization scheme is employed to systematically search for the individual components' elastic constants which give rise to a composite elastic behavior as that measured by Lin and Argon. A two-dimensional plane strain finite element analysis is performed to evaluate the composite elastic behavior for given set of constituents' elastic constants. The resulted elastic constants of semi-crystalline nylon 6 for the optimized values of crystalline and amorphous elastic properties are within 6% average error with the experimental data. The computations also reveal that high stress concentration exists in the crystalline region. Therefore, experimental measurements of plastic resistance may represent a significant underestimate of the intrinsic critical resolved shear strength of polymer crystals

Numerical solution of surface crack under cyclic hydraulic pressure loading

F 49620 93 1 0241 96/0

Influence of multiple slip systems on brittle-ductile transition in silicon

CMS 95-2266