Prediction And Test Research Of Modulus Of Quadrangular Variable Cross-section Pillar Lattice Sandwich Structure Composite

With the technological development and changes in operational thinking, therequirements of performance of modern fighter are also changed, F22, T50and J20, thefive generation machine also emerge as the times require. Requirements of mobility andstealth performance of aircraft design and manufacturing is consistent in some aspects,in some aspects is mutually contradictory. As the motor and stealth performance,composite material can be used in some aircraft to provide a new material for thedesigner, thus it has a widespread application in the aviation industry. The compositematerials can greatly reduce the body weight, improve motor performance aircraft; atthe same time, composite material has good wave penetrating which can reduce theaircraft’s radar cross section in a certain extent to improve the stealth performance ofaircraft.In this paper, the structure characteristics of the quadrangular variable cross-sectionpillar core lattice sandwich composite were analyzed as the equivalent of three layerlaminate model. The selected structural unit core cell was used to derive the four cornercolumn lattice core material and the equivalent mechanical properties of lattice corelaminate. The corresponding mechanical models were established, including the flatcompression/flatwise tensile elastic modulus prediction model, side pull/lateralcompression elastic modulus prediction model, the in-plane shear modulus, and apractical example for those models was carried out. A physical model of compositelattice core sandwich structure was established by ABAQUS, and the mechanicalproperties of four corner column lattice sandwich structures was simulated andcalculated, including the core structure of composite material and laminated flatcompression/flatwise tensile elastic modulus, side compression/lateral tensile elasticmodulus, and the longitudinal and transverse shear modulus. The predicted values werecompared with the simulation results. The result shows that the deviation betweensimulation values and the calculated values of the lattice structure is not more than20%,which means the certain reliability of those models.Ultrasonic non-destructive testing and destructive testing methods for defects ofquadrangular variable cross-section pillar core lattice sandwich composites werecharacterized; the results indicate that many defects formed during the preparationprocess exist in composite materials. Flat and side compression modulus, shear modulusof lattice core laminates were tested and compared with that of theoretical calculationand finite element simulation. The results showed that the test values have big gap withpredicted values. The test value of flat compression modulus decreased by31.8%, theside compression modulus value decreased by25.1%, and the value of longitudinal and transverse shear modulus decreased by15.8%and18.2%respectively comparedtheoretic calculated value.