层合板层内损伤检测的模态位移不平整系数法

为了准确识别复合材料损伤的位置和程度，提出一种以模态曲率差幂函数为损伤指标的新检测方法.基于ANSYS的APDL语言，应用Shell181单元建立简支层合板模型，并通过Camanho损伤准则构建层内纤维失效模型.利用模态分析获得层合板的固有频率及网格节点模态位移，应用差分法得到曲面的高斯曲率，研究损伤前后高斯曲率差随损伤位置和程度的变化规律.采用高斯曲率差的平方增加峰值与其他区域的差距，将其定义为模态位移不平整系数并进行层内损伤位置和程度检测.结果表明:模态位移不平整系数使损伤位置检测的准确性提高，且随损伤程度的增加而增大.研究结论为改进复合材料层合板层内损伤的无损检测方法提供指导.

An Unevenness Coefficient Method of Modal Displacements for Intra-laminar Damage Detection in Composite Laminates

A new detection method using the power function of modal curvature differences as damage index was proposed to accurately identify the location and extent of composite material damage. Based on the APDL language of ANSYS， the Shell181 element was used to establish the simply supported laminate model， and the intra-laminar fiber failure model was constructed according to the Camanho damage criterion. The natural frequency of the laminate and the modal displacement of mesh nodes were obtained by modal analysis. The Gaussian curvature of the surface was obtained by the difference method， and the change of the Gaussian curvature difference before and after damage with the damage location and extent was studied. The square of the Gaussian curvature difference was used to increase the gap between the peak value and that of the other regions， which was defined as the modal displacement unevenness coefficient to detect the intra-laminar damage location and extent. The results show that the modal displacement unevenness coefficient improves the accuracy of the damage location detection， and it increases with the rise of the damage extent. The research conclusions provide guidance for improving the non-destructive testing methods for the intra-laminar damage of composite laminates.