基于非接触位移测量的层压板低速冲击性能分析

为通过冲击点位移获得复合材料层压板的低速冲击性能，首先，在层压板落重冲击试验中，使用高速激光位移传感器测得冲击点背部的位移和速度；然后，基于弹簧-质量冲击模型，以冲击点位移计算了冲击接触力，并通过无损冲击试验标定了弹簧-质量模型参数；接着，模拟了有损伤冲击过程的接触力，利用实测冲击点速度响应判定了分层产生的时刻，并根据模拟结果得出了分层阈值力；最后，根据无损检测结果进行了层压板抗弯刚度的折减，使用弹簧-质量模型计算了产生冲击损伤后的接触力及能量吸收曲线，使用冲头和冲击点背部位移计算凹坑的实时深度。结果显示:结构受冲击发生分层时，由于层压板刚度的突降，冲击点速度出现剧烈震荡，该现象可以作为结构出现分层损伤的识别特征；产生冲击损伤后的接触力及能量吸收曲线的计算结果与试验测试结果吻合。计算所得凹坑的实时深度随冲击能量的变化趋势与冲击后测试的凹坑深度变化趋势一致。这些结果表明提出的基于非接触测量技术的方法可用于无法直接测量接触力情况下的层压板冲击性能分析。 

Performance analyses of laminates subj ected to low velocity impact based on non-contact measurement displacement

In order to obtain the performances of composite laminates under low-velocity impact through the dis-placement of impacted point,the displacement and velocity for the back of impacted point were measured by high-speed laser displacement sensors during drop weight impact test of laminates firstly.Then,based on spring-mass impacted model,the impacted contact load was calculated by the displacement of impacted point,and the parameters of spring-mass model were calibrated with non-destructive impact test.After that,the contact load during the im-pact process with damage happening was simulated,the time of delamination initiated was j udged by the testing ve-locity response of impacted point,and the delamination threshold load was obtained by simulated results.Finally, the reduction for flexural rigidity of laminate was conducted according to the result of non-destructive test,the con-tact load and energy absorption curves after impact damage initiated were calculated using spring-mass model,the real-time depth of indentation was calculated by the displacements of impactor and back of impacted point.The re-sults show that when the structure is impacted and delamination initiates,violent vibration for the velocity of impact-ed point appears due to the sudden reduction of laminate rigidity.This phenomenon can be used as the recognition characteristic for the delamination damage of structure initiating.The calculated results for contact load and energy absorption curves after the impact damage initiated coincide with the measured results of tests.The varying tendency for the real-time depth of indentation with the impact energy obtained by calculation is in accords with the varying tendency for the depth of indentation measured after impact.These results indicate that the proposed method based on non-contact measurement technology can be applied to analyze the impact performances of laminates under the condition that contact load can not be measured directly.