数字图像相关技术在复合材料加筋曲板压缩试验中的应用

Application of digital image correlation technology in compression test of stringer stiffened composite curved panels

对复合材料自动铺丝和手工铺丝两种T型加筋曲板进行了单轴压缩试验,采用基于数字图像相关技术(Digital image correlation, DIC)的三维光学测量方法对该型加筋曲板的局部屈曲及后屈曲波形进行实时监测,并与传统应变、位移测量结果进行了对比分析。试验结果表明:DIC能够准确捕捉整个试验过程中的位移场,使用DIC设备观测到的屈曲模态与应变片数据反映的波形具有良好的一致性;不同于传统测量方法,DIC能够准确捕捉蒙皮在后屈曲阶段的屈曲模态转换的全过程;利用DIC技术能够对试验不同时间节点(即不同载荷水平)的屈曲模态进行清晰、直观的观测,因而能够较准确地获得结构的屈曲载荷,该载荷与由应变-载荷曲线确定的屈曲载荷相比,误差小于5%。采用ABAQUS有限元软件对试验过程进行了数值仿真分析,并通过与试验结果的对比表明了计算结果、DIC测量结果与传统方法测量结果三者具有良好的一致性。

An uniaxial compression test was conducted for T-stiffened composite curved panels which were automatic fiber placement(AFP) manufactured or hand-laid. A 3D optical measurement method which was based on the digital image correlation(DIC) was used to monitor the local buckling and post-buckling, and the results were compared with that of strain gauges and displacement transducers. The results show that the displacement field can be accurately captured by DIC, and the buckling mode observed using DIC is consistent with that the values of the strain gauges reflect. Different from the conventional method of strain gauges, the whole progress of the buckling mode transition of the skin caused by the secondary instability is accurately captured by DIC. The buckling modes at different times(i.e. different load levels) are clearly and intuitively observed using DIC equipment, so the buckling load of the structure is easy to determine and the error is less than 5% compared with the load indicating the strain-load curves separation. A numerical simulation analysis based on finite element software ABAQUS was carried out. The computation results were compared with the test results, revealing that there is a good consistency among the computational results, results from DIC and results of conventional method.