Graded optimization and analysis of composite cabin based on fatigue life

To construct composite fatigue life models of three-dimensional stress state, a solution of using rigidity element and spring element to simulate the interaction between layers was proposed. Then three-dimensional finite element models were constructed by combining the interlamination models and two-dimensional plate element. A fatigue life analysis method of any stress ratio was developed with the aid of the fatigue test results and damage models of typical stress ratio, as well as the transformation theory of equilife curves. Fatigue life models of multiaxial cyclic stress were constructed by introducing compound cumulative damage. With the aid of stress analysis, failure analysis of static strength and fatigue cumulative damage and degradation models of material property, the processes of damage, the emergence and expansion of damage and the general destruction, in-plane and between layers, can be simulated. Then the fatigue life can be attained. By the contrast of the predicted values with the test results of fatigue life of laminates, the validity of the constructed models is verified. Considering the space complexity of the design variables, the two-level optimizations-system-level layout optimization and subsystem-level dimension optimization-was adopted. Adopting the self-adaption genetic algorithm, regarding the minimum mass as the objective function, the fatigue life requirement as the constraint condition, the composite cabin is optimized. The optimization framework of composite structure is built based on multiaxial stress fatigue life, which can provide references for the optimization design of composite structure.