State Transition Approach to Reliability Based Design of Composite Structures

The paper presents a new approach to the optimal design of composite structural systems in the presence of uncertainties. A progressive damage propagation model for composites, based on transformation field analysis (TFA), is used to develop a design for reliability that includes multiple failure modes typical in laminated composite structural systems. This analysis involves multiscale computations, with complex interactions between response parameters at different length scales. Not all failure modes are equally catastrophic and may only result in degraded structural performance. A design problem formulation based on a state transition approach is introduced, and allows for the handling of multiple failure modes in a rational manner. This methodology termed as a system effectiveness approach, models designer preference as to acceptability of degraded performance, and is used to develop optimal designs. A comparison of these designs against those obtained from a more widely used competing risk methodology provides insight into the advantages of the new approach. I