复合材料盒段试验夹具非线性变形机理与补强措施

Nonlinear Deformation of Rig for a Composite Wing Box Test and Its Reinforcement

在一复合材料盒段结构弯曲试验中,高载荷下试验件并未失效,但试件和夹具整体结构刚度低于预试试验值,呈现逐渐降低趋势,过大的变形消耗了作动缸行程,致使最大加载载荷低于预期值,卸载后整体结构有残余变形。根据有限元计算结果和试验数据,对多种可能的原因进行分析。结论为夹具金属盒段中,连接上、下壁板与纵墙缘条时使用了全螺纹螺栓,尽管极限强度满足要求,但螺纹在高载荷下产生了塑性变形,导致螺栓限位能力不足,夹具变形偏大。针对该原因,在不拆卸试验结构的情况下,更换夹具金属盒段中部分全螺纹螺栓为抗剪螺栓,再次进行试验。结果显示,结构变形的非线性现象消失,最大加载载荷提高16.6%,卸载后夹具无残余形变,证明了原因预测与夹具补强方案的正确性。

In the bending test of a composite wing box,the structure stiffness under high level load was lower than the value in trial test,and decreased gradually without structure damage.The larger deformation wasted the stroke of actuators and the maximum load did not reach the predicted level.After unloading,the residual deformation of the whole structure was observed.Based on the finite element analysis and test data,several possible reasons were studied.The eventual inference focused on the full-length threaded bolts connecting skin panels and beam flanges in the rigging metal box at the pin-load.The ultimate strength of bolts was enough,but the threads yielded and the bolts could not restrain the skin and beam firmly,which resulted in the larger deformation.The experiment was conducted again after the full-length threaded bolts were partly replaced by shear-bolts without disassembling the whole structure.No evident nonlinear response and residual deformation were observed in the test with the maximum load increasing by 16.6 percent,hence the inference and reinforcing method was validated.