The Research On Dynamic Response And Low-energy Impact Damage Of Composite Laminated Structures In Aircraft

Compared with metallic materials, composite has a number of advantages, such as highstrength, high stiffness, light weight and anti-fatigue, high-temperature resistance, designableproperty, which is more and more widely used in aerospace, transportation, etc. in recentyears. However, there is also fatal weakness in composite, which is very sensitive to externalimpact loading, easily causing impact damage. Therefore, deeply studying on the impactdamage of composite materials and its influencing factors, and improving its impactresistance, have important practical significance.Firstly, dynamic impact tests were conducted on composite sandwich panels with twokinds of core thickness, considering the effect of different impact energy and punch. Testcurve data such as impact force, displacement etc. and failure mode were obtained forspecimens under different experimental environment, and the variation of the dynamicresponse with the various factors was summaried.The impact test was simulated using dynamic finite element method, and the reliabilityof the numerical method was verified by comparing the simulation results and experimentalresults. On this basis, the dynamic response of a certain type of unmanned reconnaissanceaircraft composite radome under bird-strike and a military aircraft composite wing leadingedge under hail-strike were simulated. The results provide some important reference forcomposite aircraft structure design.This paper focuses on low-energy impact damage, which is more harmful to compositelaminated structures. For different mode of impact damage of composite laminated structures,we consider the laminated structure as combination of sub-layer in which the fiber-layingdirection is the same and the interface layer between the adjacent sub-layer, and establishdamage analysis model by different damage analysis method. We also put forward thenumerical simulation method for solving highly nonlinear problems such as impact damagebased on dynamic finite element analysis software LS-DYNA, including accurateconstruction of finite element model, and the entire process of numerical simulation analysis.The emerge, evolution and feature of all kinds of damage modes in composite laminatesunder low-energy impact load were studied by using LS-DYNA program, and the reliability of the damage analysis model was verified by comparing the simulation results and findingsin the literatures. The results showed that the delamination and matrix cracking damage is themain form of the low energy impact damage of composite laminated structure, and variety ofdamage modes appear at different time, the matrix cracking damage appears fristly, the matrixcrushing appears secondly, then the fiber compressive failure and little fiber fracture appears,the delamination appears last.Finally, a number of factors that affect on low-energy impact damage in compositelaminated plates were discussed, including the mass of the punch, impact energy, and materialproperties. It shows that the low-energy impact damage in composite laminated plates is notdirectly relative to punch mass, impact velocity, but rather related to impact energy; theimpact damage area is increasing with the increase in impact energy, there is a approximatelinear relationship between delaminaton area and impact energy, and there is an energythreshold in delamination; in addition, composite materials with high modulus and highstrength can restrict low-energy impact damage more effectively.The results make the foundation for researching the residual strength and fatigue life ofcomposite structures which is next step of work.