Study On The Low-Velocity Impact Damage Characteristics Of Plain-Woven Composite Laminates

Plain-woven composite materials have been widely used in the field of aeronautics and astronautics engineering, mechanical engineering and military industry due to its high strength to weight ratio, excellent in-plane mechanical properties and so on. But the properties of plain-woven composite materials, like conventional composites, will decline obviously when they subject to low-velocity impact, because of the matrix cracking, delamination and fiber breakage within the structure, which can affect their bearing capacity and service life.Some issues on low-velocity impact of T700SC-12k-50C/#2510 plain-woven composite laminates have been investigated in this paper: the impact characteristics of three typical laminates through the low-velocity impact tests; the damage characteristics by using ABAQUS finite element software to simulate the impact process; the relationship between residual strength and impact energy, and the influence of temperature and humidity conditions, by the compression tests after impact.(1) The critical impact energy of three typical laminates is determined. The front surface shows indent depth and crack in different degrees, the back surface shows fiber breakage damage when the impact energy exceeds the critical impact energy.Indent depth curve shows obvious turning point due to fiber breakage, three typical laminates show different turning point corresponds to the impact energy because of the different thickness and layer. After the turning point, matrix cracking becomes more serious.(2) Introducing the Hashin in-plane damage criterion and the interlayer cohesive unit to simulate the process of the internal damage of laminated plates after low-velocity impact. Setting up two models: one model that only considered in-plane damage and the other model both considered in-plane damage and interlayer damage.The former one shows that fiber fracture and matrix cracking damage usually occur at the center of the impact location and along the width direction of ?45?, under the serious damage conditions, the surface shows "X" shape. The latter model shows that the shape of damage area is similar to the double leaf or peanut. And delamination damage starts from the back surface to the front surface. Front surface delamination damage region is smaller than the back ones, but more serious. The numerical simulation of the damage area is basically consistent with the ultrasonic C scan projection area.(3) The relationship between impact energy and the residual strength is determined: when impact energy turns higher, the impact damage becomes more serious, residual strength declines more, and the withstand ability under compression load becomes worse. But the compression failure modes isn't affected by the low-velocity impact, it shows layered extensions, buckling damage and eventually occurs shear delamination failure. But the failure characteristics and the failure regions are different.(4) Under the same impact energy, due to the brittleness drops the moisture absorption laminates are less sensitive to impact damage than no moisture absorption ones, but the compression strength declines obviously.