Beam analysis of angle-ply laminate end-notched flexure specimens

Analysis and experiments on quasi-unidirectional and angle-ply laminate end -notched flexure specimens are presented. The analysis is based on laminate d beam theory incorporating first-order shear deformation theory. Complianc e and strain-energy release rate determined for relatively thin unidirectio nal and angle-ply laminate ENF specimens were in good agreement with a prev ious classical plate theory formulation. For thicker laminates, however, ef fects of shear deformation on the compliance of the ENF specimen become sig nificant. An experimental study on glass/polyester quasi-unidirectional and angle-ply laminate ENF specimens was conducted. Specifically, [0](6), [+/- 30](5) and [+/-45](5) laminates with mid-plane delaminations were considere d. Experimental compliance data agreed well with analytical predictions. Th e fracture toughness increased with increased angle theta at the +/-theta i nterface. This is attributed to the fracture work associated with the debon ding of transversely oriented fiber bundles in the quasi-unidirectional pli es. The angle-ply laminates displayed more yam debonding than the quasi-uni directional laminate. For all laminates it was observed that the crack prop agated in a non-uniform manner which is correlated with elastic coupling ef fects with cracked regions of the laminate beams. (C) 1998 Elsevier Science Ltd. All rights reserved.