Research On Impact Damage Of Laminates And Fatigue Life Of Impacted Laminates

The application of composite laminates in aircraft structures is becoming moreand more widely, and laminates are often impacted by foreign object. Laminatesincluding damage are in relation to the safe use of the structure. So the study on theimpact damage of laminates and fatigue life after impact is very necessary.Based on a drop hammer impact test of a standard size typical plyed laminatedplates, and a nondestructive testing of the laminates using ultrasonic immersion Cscan, we get parameters of the impulse response, including the impact contact forcecurve, the impact dent depth of laminated plate and damage area results. By theresidual compressive strength test of the composite laminates after impacted, we getthe residual compressive strength values of laminates with impact damage. On thisbasis of the strength design value, fatigue tests were carried out on the compositelaminates, and we get the fatigue damage evolution, the fatigue life under differentfatigue forces and the fatigue life curve of S-N.Based on the impact experiment results of composite laminates, we establishedthe3-D finite element simulation model of laminates impact, the whole impactprocess is simulated by finite element method. Then we get the impact responsecurve, contact force curve and the layer failure mode and interlaminar delaminationdamage. Damages like fiber tensile, fiber compression, matrix tensile, matrixcompression and the delamination size and distribution are obtained. By comparingthe finite element method result with test result, we verify the validity of thesimulation model.Based on the fatigue life test of laminates after impact, we established theimpacted laminates fatigue life finite element simulation model. By setting theparameters, the impacted state is setted as fatigue initial state. We get the fatigue lifeunder different fatigue load, and render the impact damaged laminates fatigue lifecurve of S-N. Comparing with the test result, we verify the validity of the simulationmodel. So, we provide a fast, accurate finite element calculation method of fatiguelife of impact damaged laminates.