Delamination analysis of a laminated composite tapered beam

A laminated composite tapered beam subjected to tension and bending is investigated for the interlaminar stress distribution and strain-energy-release rate due to effects of ply dropoff and free-edge using finite element and sublaminate analyses. The tapered laminate consists a S2/SP250 glass/epoxy with a {dollar}pm{dollar}45{dollar}spcirc{dollar} group of plies dropped in one distinct step, 20 ply-thicknesses apart, thus forming a taper angle of 5.71 degrees.; The laminate is finite-element modeled in longitudinal and edge view cross-sections, respectively. Steep gradients of interlaminar stresses suggest the existence of stress singularities at the points of material and geometric discontinuities created by the internal plydrops.; In both tension and bending cases, the strain-energy-release rate for a delamination growing in the thin region consists predominantly of a Mode I component. For a delamination growing along the tapered region, the Mode I component of the strain-energy-release rate decreases with increasing delamination size until eventually it is all Mode II. These results suggest that the delamination initiating at the taper root will be self-arrested if applied load remains unchanged.; Sensitivity analysis of the interlaminar normal stress and total strain-energy-release rate is investigated for variation of taper angle as well as ply orientation. Explicit equations for this analysis are derived. The results indicate that the interlaminar normal stress is more sensitive at the taper root for a given change in the taper angle. The variation of total strain-energy-release rate is less sensitive at that location. Variation of the interlaminar normal stress is less sensitive as the taper angle decreases. Both interlaminar normal stress and total strain-energy-release rate are more sensitive for variation in the outer ply angle change than at the other locations. It is also found that the degree of sensitivity due to bending is much less.