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

A design optimization process for elasto-plastic material behaviour of laminate composite structures, made of thermoplastic resins, is described. The approach considers two optimization levels. At the first level the geometric linear behaviour under elasto-plastic loading conditions is adopted in order 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 zones using only the anisotropic material properties. At the second level the ply thickness of the plates or shallow shells and the height and width of the reinforcement beams are changed to structure weight minimization, under the constraints of maximum allowed displacement or maximum strain-stress level related with amount of plastic zone, without structural plastic collapse or geometric instability in plastic loading conditions. It is expected that contradictory objectives, as minimum elasto-plastic energy and structural weight, are satisfied.