Abstract: A fiber reinforced composite structure for transmitting high shear loads includes a laminate with an edge defining a buttress groove. The buttress groove includes a pressure flank oriented substantially perpendicular to a longitudinal axis of the structure to transmit shear loads in one direction only. The laminate is formed of a plurality of plies having fibers disposed in a matrix material at angular orientations relative to the longitudinal axis of the structure. A first plurality of the plies have fibers oriented parallel to the longitudinal axis and a majority of the other plies have fibers oriented at an angle .theta. relative to the longitudinal axis corresponding to a direction of the largest tensile component of the shear load.

Abstract: To determine the optimum load a laminate member or element is capable of bearing, a three-dimensional progressive analysis is proposed in which the stress and strain states of each ply of the laminate are subjected to failure criteria. If there is failure, new ply stiffness parameters are calculated. Thereafter, the ply is tested with the new parameter until the optimal load is determined. If no failure is detected for a given stress and strain for the ply then the load may be incremented and again applied to the ply, for further testing. Alternatively, the same load may be applied to the ply for a further period of time, until the optimal load is determined and/or the analysis is deemed to be finished.