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A technique to determine which loads or combination of loads that contribute to the fatigue damage of a component is proposed. Knowing critical loads allows a designer the opportunity to better optimize designs. This information also helps accelerate durability evaluation procedures (both analytical and laboratory based). The technique involves the use of a computer-based FEA method incorporating conventional fatigue life prediction algorithms to assess component durability on an element-by-element basis. After a global fatigue analysis of the entire component, the critical element(s) are identified. A statistical approach, based on a factorial design of experiments, is then applied to assess the effect of varying combinations of component input loads on the predicted durability of these elements. This approach provides a methodology for keeping computational time to a minimum whilst developing a comprehensive understanding of the behavior of the critical areas.

Displacement-based isoparametric finite elements are developed and applied to problems of thick and thin laminated composite plates and shells. Transverse shear deformation, material anisotropy, and bending-extensional coupling are accounted for. Curvature and lamination parameters may vary smoothly or discontinuously. These elements have been implemented in the NISA finite element program and several example problems are discussed. A method for calculating the exact distribution of transverse (interlaminar) shear stresses in composite laminates is discussed and an example problem is solved using the present elements. Agreement with an exact solution is excellent.

This paper identifies significant features of automotive composite structural response, discusses the computer implementation of analysis methods to solve the composite structural response problem, and evaluates a number of existing computer programs with respect to their abilities to model composite structures.