基于虚拟裂纹闭合技术的应变能释放率分析

Analysis of strain energy release rate based on virtual crack closure technique

基于虚拟裂纹闭合技术(VCCT),建立了复合材料层合板层间裂纹尖端的应变能释放率(SERR)三维有限元计算模型。该模型考虑了裂纹尖端大转动和离散单元形状变化对应变能释放率计算的影响,修正了裂纹尖端应变能释放率的计算方法。利用该模型计算了裂纹长度为15 mm和35 mm时纯Ⅰ型和纯Ⅱ型的应变能释放率,纯Ⅰ型应变能释放率分别为207 J/m2和253 J/m2;纯Ⅱ型应变能释放率分别为758 J/m2和1040 J/m2;计算值与试验值吻合得很好。同时,该模型计算了混合型不同比值R=(GⅡ/GⅠ+GⅡ)的长裂纹层合板层间断裂过程的应变能释放率,其中Ⅰ型和Ⅱ型应变能释放率计算值与试验平均值的最大误差为11.4%,最小误差为0.4%。该模型能有效计算裂纹尖端的应变能释放率。

A three-dimensional （3D） finite element （FE） model for calculating the strain energy release rate （SERR） at the crack tip of composite laminates was built up based on the virtual crack closure technique （VCCT）. The model involved effects on SERR computation by large rotation of the crack tip and variety of discrete element shapes. The method of SERR calculation at the crack tip was modified. When crack lengths were 15 mm and 35 mm, the SERRs of pure mode Ⅰ and mode Ⅱ were computed with this model. The SERRs of pure mode Ⅰ are 207 J/m^ and 253 J/m^ , and the SERRs of pure mode Ⅱ are 758 J/m^ and 1040 J/m^. The predicted values agree with experimental data. At the same time, the mixed-mode SERRs of varied ratios R= （GⅡ/GⅠ＋GⅡ） with large cracks were also computed. The error range between predicted SERRs and experimental date is 0.4% to 11.4%. This model can exactly calculate SERRs at the crack tip.