Optimal design of beam reinforced composite structures under elasto-plastic loading conditions

A design optimization process for elastoplastic material behaviour of lamin ate composite structures, made of thermoplastic resins; is described. The a pproach considers two optimization levels. At the first level the geometric linear behaviour under elasto-plastic loading conditions is adopted in ord er to obtain the optimal solution as a function of ply angles of the plates or shallow shells. At this stage the objective is to recover the plastic z ones using only the anisotropic material properties. At the second level th e ply thickness of the plates or shallow shells and the height and width of the reinforcement beams are changed to structure weight minimization, unde r the constraints of maximum allowed displacement or maximum strain-stress level related with amount of plastic zone, without structural plastic colla pse or geometric instability in plastic loading conditions. It is expected that contradictory objectives, as minimum elasto-plastic energy and structu ral weight, are satisfied.