DESIGN WITH COMPOSITES: MATERIAL UNCERTAINTY IN DESIGNING COMPOSITES COMPONENT

What is it about?

The article is organized as follows: first, the sources of uncertainty for composite structures are identified in the section titled ‘‘Sources of Uncertainty.’’ Uncertainty-analysis-based sensitivity is presented in the section titled ‘‘Uncertainty Analysis Based on Sensitivity’’ with local importance measure of uncertainty and global sensitivity analysis (GSA) described and applied to composite structures. The effects of uncertainty propagation on the response of composite structures under nonlinear geometric behavior, in particular, in the presence of buckling loads, are analyzed in the section titled ‘‘Uncertainty Propagation in Composite Structures with Nonlinear Behavior.’’ The reliability assessment of composite structures is presented in the section titled ‘‘Reliability Assessment of Composite Structures,’’ and the influence of multiple failure modes and uncertainty in reliability assessment are studied. The final conclusions on material uncertainty consequences on the design of composites are presented in the section titled ‘‘Conclusions.’’

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Why is it important?

The importance measures of input variables on structural response based on numerical results were established and discussed as functions of anisotropy of composite materials. The Global Sensitivity Analysis (GSA) is implemented as a function of the ply angle. The global variance of the Tsai number was explained by a first-order sensitivity index of Sobol for input variable groups. The requirements for global variance methods are discussed by comparing the results obtained from proposed methodologies. The results show that a first-order local method is acceptable to analyze the uncertainty propagation on the response of angle-ply laminates. The effects of uncertainty propagation on the response of composite structures under nonlinear geometric behavior were analyzed. In particular, the effects of uncertainty into material properties on the response of stiffened shell composite structures supporting buckling loads were analyzed. As a result of the associated analysis and design complexity, the structural response becomes highly unpredictable because uncertainties in geometry, loading, or material properties can completely change the failure path. Thus, a probabilistic failure analysis of composite structures is needed. The reliability assessment of composite structures was introduced, and difficulties associated with structural reliability definition were identified. It can be concluded that the Most Probable failure Point (MPP) search of composite structures introduces new uncertainty factors associated with multiple failure points, influencing the structural reliability system. The performed study demonstrated that the reliability index is very sensitive to uncertainty in mean values of certain mechanical properties of composites, such as transverse strength, longitudinal elastic modulus, and transversal elastic modulus.

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