Characterization of Mode II Delamination Growth in Glass/Epoxy Composite Cylinders

Abstract

Delamination growth in filament wound composite cylinders has been characterized for shear (mode II) loading. Beam specimens were machined from cylinders with embedded aluminum films to define an initial delamination. The specimens were machined so that the delamination was at one end, and the beam axis parallel to the cylinder axis. Analysis of compliance and energy release rate of beam specimens configured in ENF mode II loading was performed based on a formulation for cylindrical shear-deformable shells. The contribution from residual thermal stress to the energy release rate was examined, but found negligible for the [±θ]n (n = 6 and 12) glass/epoxy specimens under consideration (θ = 30°, 55° and 85°). Contoured loading bars and supports were prepared for experimental ENF testing of beams with curved cross-section machined from composite cylinders. The experimental compliance data were in close agreement with predictions over the ranges of crack lengths, beam thicknesses, and ply angles examined. The mode II fracture toughness increased with increased angle θ at the ±θ interface.