Optimum in situ strength design of composite laminates .2. Optimum design

The stress norm developed in Part I is incorporated into the formalism of an optimization problem in order to enhance the load bearing capacity of multidirectional laminates. The optimization problem is solved for symmetric laminates subjected to any combination of in-plane loads. In this problem, the stress norm is the design objective to be minimized whereas the ply angles and thicknesses are the design variables. The solution of the formulated min{max} optimization problem is obtained by the bound-formulation method and mathematical programming. The gradients of objective functions and constraints needed in this method art calculated by a mixed analytical/numerical procedure. The results show that the optimization technique based on the in situ laminae strength parameters is a promising tool in the design of the composite laminates. The load bearing capacity of an optimally designed laminate can be increased several fold compared with that of a conventionally designed laminate.