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应变不变量失效理论(SIFT)是一种新型的基于物理失效模式的复合材料强度理论,被广泛应用于复合材料结构失效分析。首先,为了提高理论分析的精度,SIFT被扩展用于分析碳纤维增强树脂基复合材料(CFRP)层合板开孔结构的静载压缩逐步失效机制和强度。开发的SIFT实施方法包括材料强度表征和结构强度预测两个部分。结构强度预测是基于ABAQUS平台并使用Fortran语言编写用户自定义材料子程序(UMAT)实现的。随后,将SIFT预测值与经典复合材料强度理论Tsai-Wu和Hashin理论的预测结果和试验结果进行了对比,结果显示SIFT预测的精度最高。同时,基于SIFT对静载压缩下的AS4/3501-6层合板开孔结构从初始失效到最终失效的失效机制演变进行了详细的分析。最后,将SIFT预测的AS4/3501-6层合板开孔结构静载压缩的失效机制与试验结果进行了对比。结果表明SIFT预测的逐步失效机制与试验结果相吻合,所得结论为CFRP结构强度的预测提供了新思路。
The theory of strain invariance (SIFT) is a new theory of strength of composites based on physical failure mode, which is widely used in structural failure analysis of composite materials. First, in order to improve the accuracy of theoretical analysis, SIFT was extended to analyze the progressive failure mechanism and strength of static loading of the open-cell structure of carbon fiber reinforced resin matrix composite (CFRP) laminates. Developed SIFT implementation methods include material strength characterization and structural strength prediction of two parts. Structural strength prediction is based on the ABAQUS platform and written using the Fortran language user-defined material subroutine (UMAT). Subsequently, the SIFT predictions are compared with those predicted by the Tsai-Wu and Hashin theories of classical composites strength theory. The results show that SIFT predicts the highest accuracy. At the same time, based on the SIFT, the evolution mechanism of the failure mechanism of AS4 / 3501-6 laminate under static load from initial failure to final failure was analyzed in detail. Finally, the failure mechanism of SIFT-predicted AS4 / 3501-6 open-cell structure with static load compression is compared with the experimental results. The results show that the gradual failure mechanism of SIFT prediction agrees well with the experimental results, and the conclusions obtained provide a new idea for the prediction of structural strength of CFRP.