Study On High Speed Impact Damage Of C Fiber Reinforced Composites Plate Using Discrete Element Method Simulation And Experimental Research

C/C composites materials is in the nature of high hardness、high strength、corrosionresistance、friction and wear resistance, hot resistance and other excellent properties, and lightweight(1.7g/cm3), good stability, strong designability. It has a wide range of applications in nationaldefense field and the life of people. C/C composites often encounter various collision in the processof manufacture, use and maintenance, and research on its impact damage becomes a hotspot incurrent. Impact could be divided into low speed impact and high speed impact, many scholars athome and abroad studied low velocity impact damage, but less research on high speed impact. Dueto high impact velocity, impact time is very short, and the process of impact is very difficult to beobserved in experiment, so we need use computer to simulate the process of high velocity impactdamage, but there is not a research method could simulate the process of crack production andextension well in high speed impact.The discrete element method (DEM) is applied to study multilayer C/C composites high speedimpact injury. Firstly, model of C/C composites should be established according to its size andstructure using parallel bond model of bonded-particle model (BPM), fiber and matrix could bedistinguished by different colors, and interface (fiber/matrix interface and interface layer) could becharacterised by some model in the contact area between grains contacted with different colors.Interface element constitutive law was simplified to bilinear constitutive model by many scholars,justly displacement softening contact model in PFC2D is very similar to the bilinear constitutivemodel of interface, so the model can be used in the interfaces, and which strength could becalibrated by using the Double Cantilever Beam virtual test (DCB) and microbond test. Bycomparison between mechanical test (uniaxial compression and single edge notched beamexperiment) and the test in DEM simulation, DEM static mechanics model of multilayer C/Ccomposites matches its macro mechanical properties well. The phenomenon of the pendulum impactexperiment and its simulation results in DEM is very anastomotic, which verify the model is stillvalid for the dynamic impact damage. The model can be used in simulation of the high velocityimpact damage to predict its damage，and research under different conditions (different impactspeeds、shapes of punch and C/C composites layers), could reveal injury mechanism and law ofmultilayer C/C composites impacted at high speed:(1) in the same punch and C/C layer, the impactvelocity is higher (high speed), the impact enegy consumed by C/C composites is bigger, but theimpact injury has a tendency to reduce;(2) in the same impact velocity (high speed) and C/C layer,the punch is more sharp, the impact enegy consumed by C/C composites is smaller, but with the increase of impact velocity, gap of impact energy consumed has a tendency to increase, and thetendency of surface damage is reduced;(3) in the same punch and impact velocity (high speed), C/Ccomposites layer is more, more impact energy should be need for penetrating it.Then the C/SiC ceramic matrixcomposites interface was explored, convergence of DCB anddroplet debond testing were made a detailed study. Finily, the DEM application in composites wereprospected, and the error and defect were analyzed in the article later.