Abstract:

ESDU 91003 uses a fracture mechanics approach to predict the axial load (tensile or compressive) at which delamination will occur in a laminated plate tapered in thickness by stopping off, or dropping, layers. The load is applied along the taper, and delamination occurs in the high stress regions caused by the discontinuity at the stopped ply. Two cases are considered: zero transverse strain for a wide plate or zero transverse load for a longitudinal strip. The method requires a value for the critical strain energy release rate between layers, and notes are included on how that may be measured experimentally. Guidance is given on good design practice in tapering a laminate to reduce the likelihood of delamination. Results from the analysis are compared with limited experimental data from the literature, and agreement is seen to be reasonable. A Fortran program is provided as ESDUpac A9103 and is initially set to handle up to 200 layers (100 continuous and 100 dropped) of 50 different fibre orientations or materials, although those limits can be increased if desired. The input to and output from the program are explained and illustrated with a worked example, and the various warning messages that may be output are discussed.