Metamodels for the Optimization of Damage-Tolerant Composite Structures

The research here presented regards the development of an optimization technique for the design of damage-tolerant stiffened composite structures subjected to combined axial compression and shear loading. Some techniques are already has been presented in literature regarding the optimization of composite stiffened panels [1-3]. The proposed methodology wants to satisfy a number of different performance requirements, such as buckling load and post-buckling stiffness for various states of damage. In particular, the design must be tolerant of predetermined degradation, due to disbonding between the skin and the stiffeners. The results from a comprehensive set of benchmark studies are summarized to establish the accuracy and validity of proposed material softening approach in order to simulate material degradation. A metamodelling method has been introduced to optimize a composite stiffened box structure for maximum reliability, while accounting for predetermined degradation. This approach is based on the combined use of probabilistic structural analysis, sampling of computer experiments and approximations of the response functions. A set of numerical experiments has been complemented through experimental tests performed at Politecnico di Milano, using dedicated test equipment.