Damage Resistance Analysis Of Laminates Subjected To Low Velocity Impact Based On Displacement Measurement And Test Technology Of Small Mass Impact

The high-speed laser displacement sensor is employed to record the displacement and velocity of the impacted point of laminates subjected to drop weight test.The delamination response is shown by the fluctuation of the velocity of the impacted point when the flexural rigidity of the laminate drops off due to the delamination initiation and propagation.The contact load is obtained by the displacement of the impacted point based on spring-mass model and the model is calibrated through the impact test without damage occurring.The delamination threshold load(DTL)is obtained by identifying the delamination response of the velocity of the impacted point.The contact load and energy absorption after the delamination initiation are obtained by reducing the flexural rigidity of the spring-mass model according to C-scan results.Simulated results coincide with test data from a commercial impact tester.Consequently,the indentation during impact is obtained by the displacement of the impactor and the impacted point.The variation of the real-time indentation with the impact energy is coincide with that of the indentation measured after the impact.This non-contact measurement technology can be applied to the analysis on damage resistance to low velocity impact when the contact load is immeasurable.The small mass impact test of swing-arm type was designed consisting of impact device,scale device and support device.The impact energy,ranging from 0~3J,is generated by the deformation of torsion spring.The composite laminate is subjected to the transverse impact.The small mass impact tests are conducted by the device,including tests on the force sensor,steel plates and laminates.The strain response of the impactor and response of the force sensor are recorded by the data acquisition system.The period of the contact load obtained from strain coincides with that obtained from force sensor and the amplitude of them are almost the same.The contact load of steel plate subjected to impact calculated by strain response agrees with FE results.This experimental technology can be applied to the study of small mass impact of structure.