Characterization of mode II delamination growth in glass/epoxy composite cylinders

Delamination growth in filament wound composite cylinders has been characte rized for shear (mode Ii) loading. Beam specimens were machined from cylind ers with embedded aluminum films to define an initial delamination. The spe cimens were machined so that the delamination was at one end, and the beam axis parallel to the cylinder ax is. Analysis of compliance and energy rele ase rate of beam specimens configured in ENF mode II loading was performed based on a formulation for cylindrical shear-deformable shells. The contrib ution from residual thermal stress to the energy release rate was examined, but found negligible for the [+/-theta](n) (n = 6 and 12) glass/epoxy spec imens under consideration (theta = 30 degrees, 55 degrees and 85 degrees). Contoured loading bars and supports were prepared for experimental ENF test ing of beams with curved cross-section machined from composite cylinders. T he experimental compliance data were in close agreement with predictions ov er the ranges of crack lengths, beam thicknesses, and ply angles examined. The mode II fracture toughness increased with increased angle theta at the +/-theta interface.