纤维增强涡轮轴结构失效模式分析方法及试验验证

针对连续纤维增强复合材料涡轮轴结构失效模式分析问题,基于宏-细观力学跨尺度分析方法,建立细观力学代表性体积元(RVE)模型,通过编程模拟实现模型的周期性边界条件,计算纤维增强复合材料应力响应,将其均值应力转化为真实应力,确定失效包线。建立连续纤维增强轴结构力学模型,计算轴结构在扭转载荷下的应力响应。通过复合材料层合板主偏轴关系应力转化,将危险单元各方向宏观应力响应计算结果转化到细观力学RVE模型上,即为细观力学RVE模型受载情况。结合细观力学失效边界确定复合材料轴结构危险位置失效模式,当扭转载荷达到5 000～5 500 N·m之间,复合材料最外层即层6(+45°)首先达到基体拉伸失效载荷。开展复合材料轴结构失效模式试验,在扭转载荷达到6 000 N·m时,声发射信号相互叠加,大部分均为中频信号,中频信号多为基体、界面开裂信号。与模拟仿真计算结果对比分析,验证连续纤维增强复合材料涡轮轴结构失效模式分析方法的有效性。利用所建立模型预测了某型发动机低压涡轮轴的失效载荷及失效模式。

Method of failure mode analysis and test verification for fiber reinforced composites turbo-shaft structure

For continuous fiber reinforced composites turbo-shaft structural failure mode analysis, based on the macro-mechanics and meso-mechanics analysis method of cross-scale, a micro-mechanics representative volume element (RVE) model was established, through programming and simulation, the periodic boundary conditions of model were realized, the stress response of fiber reinforced composites was calculated and the mean stress was converted into real stress, then the failure envelope was determined. It established mechanical model of fiber reinforced composite shaft structures, and the principal stress response was calculated. Through the transformation of the principal-partial axial stress for the composite laminated plates, the macroscopic stress response calculation results of the dangerous elements in all directions were transformed into the microscopic mechanics RVE model, reflecting the microscopic mechanics load condition of the RVE model. The failure mode of composite shaft structure at dangerous position was determined by the failure boundary of micro-mechanics; when the torsional load was between 5 000-5 500 N·m, the outermost layer of the composite, also the layer 6 (+45°), reached the tensile failure load of the matrix firstly. The failure mode test of composite shaft structure was carried out; when the torsional load had reached 6 000 N·m, acoustic emission signals stacked with each other, most of which were intermediate frequency signals, of which most were matrix and interface cracking signals. Then compared with the simulation results, it verified the effectiveness of the failure mode analysis method. The failure load and failure mode of a certain engine low pressure turboshaft have been predicted by using the proposed model.