This paper deals with the optimal design of deep submarine exploration housings and autonomous underwater vehicles. The structures under investigation are thin-walled laminated composite unstiffened vessels. Structural buckling failure due to the high external hydrostatic pressure is the dominant risk factor at exploitation conditions. The search of fiber orientations of the composite cylinders that maximize the stability limits is investigated. A genetic algorithm procedure coupled with an analytical model of shell buckling has been developed to determine numerically optimized stacking sequences. Characteristic lamination patterns have been obtained. FEM analyses have confirmed the corresponding significant increases of buckling pressures with respect to initial design solutions. Experiments on thin glass/epoxy and carbon/epoxy cylinders have been performed. The measured buckling pressures appear to be in good agreement with numerical results and demonstrate the gains due to the optimized laminations

This study is concerned with the viscoplastic behaviour of polymers. A modified viscoplastic Bodner–Partom model was extended to include successively the post-yield (strain softening and strain hardening) and the pre-yield behaviour. In order to identify material parameters of the constitutive law, an analytical scheme and a numerical method based on evolutionary algorithms were developed. The capacity of the proposed viscoplastic approach is investigated for a representative glassy polymer (polycarbonate). The results and the efficiency of both approaches are discussed.

No abstract

No abstract

No abstract