Surface Damage Of Glass Fiber-Epoxy Composite With Low-energy Impact

Surface damage is the most direct part of when composite material faces impact, and also the most serious one. The damage is most obvious from the appearance. Observing and describing that part and establishing the connection between the surface damage and energy will be more significant.Under the circumstance of processing property and mechanical properties that satisfied the requirement of the experiment, this article chose epoxy resin as the matrix material and glass fiber as the reinforced material, chose contact molding process, and completed the specimen which required by impact test, by layer design. This research belongs to foundation work and exploration work of composite damage behavior.This article selects the free-fall impact tester to test, using digital microscope to discribe the characteristics of damage morphology, through self-made through-injury detector for detecting the leakage of the specimens.Through the test found that when the impact energy is low, the surface damage of both two types of board are not serious. When the impact energy increases, the surface damage also begins to increase, and resin surface begins to crack. When the impact energy increases to a certain degree, layering appears and cracking expands.When the impact energy increases, the pit area and the pit depth is also increasing, and it is approximate to linear growth. When the impact energy breakthrough 6.75 times thick of laminated board, two types of board pit area growth begin to decrease, the most obvious change trend is unidirectional laminate, woven roving laminate pit area growth into a uniform but haven’t changed much. Impact energy from smallest to largest, pit area changes are more than 150%. In addition, when the impact energy arrive at 6.75 times thick of laminated board, the depth of the pit appeared inflection point, the process is like steel in tensile test during submission process.Viscoelastic is the spiecal characteristics of composite material, it makes the indentation depth change as time accumulates after impact. 1 hour after impact, the pit depth changes in small variations; from one to three hours, the indentation depth change is much more obvious; from three to six hours, indentation depth changes dramaticlly; from the sixth hour, the indentation depth is relatively stable, basically no change; after a long period, there will be still small change in the indentation depth. Overall, from the initial to the end, the pit depth shrinks but hasn’t changed much. In addition, rebound of different materials and different layers of the specimen will be different.By collecting morphology characteristics of laminated plate surface damage, according to its surface damage morphology characteristics, the paper established the linear relationship between impact energy and the pit area, the initial depth of the pit, the eventual depth of the pit, provided the basis for estimating the surface damage degree of composite material and its energy, and also porvided the quantitative characterization of low-energy impact on surface damage of composite laminated plate.