基于最终层失效的复材舱段可靠性分级优化

Reliability based bi-level optimization of composite cabin based on the last layer failure

基于基体破坏和纤维断裂2种失效模式,采用验算点法求解复材单层可靠度。基于最终层失效假定,提出把结构看作由串联子系统组成的并联系统,结合材料刚度比率退化准则和单层可靠度理论,采用概率逐步失效分析方法,计算出主要失效链,从而得出结构的失效概率。复材舱段设计变量复杂,提出二级优化方法:一级为系统级布局优化,对加强筋截面形状、位置的确定等参数进行优化;二级为子系统级尺寸优化,对筋截面尺寸、复材各铺层厚度等参数进行优化。采用自适应随机搜索遗传算法,以复材舱段质量最小为目标函数,以可靠度要求为约束条件,对存在初始缺陷的复材舱段进行优化,为复材舱段优化设计提供参考。

The reliability of composite monolayer was solved on the basis of two failure modes of matrix damage and fiber breakage by adopting the design point method.The idea of taking the structure as parallel systems that were constituted by series subsystems was put forward based on the hypothesis of the last layer failure.The main failure sequences can be figured out through combining the material stiffness ratio degradation criterion with monolayer reliability theory,and adopting the probability gradually failure analysis method,then the failure probability of structure can be worked out.Due to the complexity of design variable space of composite cabin,the idea of two-level optimization method was put forward：the first level was system-level layout optimization,which optimized some parameters,including profile shape of stiffener rib,the parameters of position,etc.The second level was subsystemlevel size optimization,which optimized some parameters,including sectional dimensions of stiffener rib,each layer＇s thickness of composite,etc.Regarding the minimum mass of composite cabin as the objective function and the requirements of reliability as the constraint condition,the composite cabin with initial imperfection can be optimized by means of employing the genetic algorithm of self-adaption random search.The method of optimization can provide references for optimization and design of composite cabin.