THE RESIDUAL STRENGTH TEST AND ANALYSIS OF COMPOSITE RUDDER AFTER - PDF document

18 TH INTERNATIONAL CONFERENCE ON COMPOSITE MATERIALS THE RESIDUAL STRENGTH TEST AND ANALYSIS OF COMPOSITE RUDDER AFTER LIGHTNING STRIKE X.Chen 1 *, G.Liu 1, H.Wang 1 1 School of Aeronautics and Astronautics, Shanghai JiaoTong University, 800 Dongchuan Road, 200240, Shanghai, P.R.China * Corresponding author( chenxiuhua@sjtu.edu.cn ) Keywords : residual strength; static test; FEA; composite rudder; lightning strike 1 Introduction composite rudder structure. The FEM result During the past decade years, the use of shows good match with the test results. advanced composites to build civil aerocraft 2 Specimen of the Static Test components became an attractive topic of A light strike test was simulated with high research for many structural engineers. voltage electrical method to prefabricate the Composite laminate structures provide several damages. After the light strike, there are nine attractive features including its lightweight, high strike damages in the laminate skin of the specific stiffness and strength, compared to honeycomb sandwich plate. To determine the current aluminum materials, as well as its delamination area of each strike damage point, superior corrosion resistance properties that is the ultrasonic C-scan technology is used. The preferred in harsh environmental conditions. light strike damage points and shape are shown However, from the recent research work, the in Fig.1. most critical disadvantage of the resistance to widely use in primary aero structures is the 3 Test Configuration interface crack, especially the delamination after Recent test philosophy in the composite impact or strike. structure programs [2][3] is also followed here. From the federal airworthiness regulation [1], The rudder is installed vertically in the real part 25.581. “The airplane must be protected aircraft fin structure while its position is against catastrophic effects from lightning and changed and fixed by a set of jigs horizontally designing the components so that a strike will in this test program for the convenience of fix not endanger the airplane.” In this paper, we the load servo control actuators. present an analysis and test project for a There are three load cells mounted to the strong composite rudder for ARJ21. back to get the reaction force of the rudder Internal damage in composites is often initiated which simulate the actuators of the rudder. The as delamination due to strike impact. The connection beam has the function of supporting delamination is very complex and usually the rudder. On the front beam of the rudder, reduces the compressive strength. Since the there are six hinge support beam unit welded to rudder is designed with rigid structure principle, a thick steel plate which mounted on the strong even though there are some local damage area in back. The beam units are jointed to the ruder the rudder, it still work functionally, thus the with shear bolts. All the beams are designed and rigid degradation of the laminates after strike their rigid are provided by virtual test of the impact is more necessary. rudder before manufacturing. The rigid degradation factor of ply is calibrated Consider not to destroy the strike damage, the with the coupon test results with parametric pressure loads are calculated to one side. On the calculation method. Then use the equivalent laminate skin of the composite rudder, 61 pieces rigid result for the finite element analysis of the

adhesive tape are used to simulate the local simulate the composite laminates. The CBEAM aerodynamic pressure load. Five levels and CBAR elements are used for the jig models traditional load leverage devices are used. At and the ribs of the rudder. Damage introduced the end of the lever, two servo actuators are by lightning stroke is simulated by stiffness installed in the reaction ground for the design reduction method during the process of limit load of the composite rudder. constructing the finite element model, and the Fig.2 shows the schema and real installation of coefficient of reduction is determined by FEA the static test. results with the data from the C scan and calibrated with coupon test results. 4 Test Control and Data Acquisition Systems The finite element model is shown in Fig.4, Loading signals are generated in a powerful and which indicates the load vectors and the flexible multi-channel control system, MTS constraint conditions. The loading on the rudder FlexTest 200, under the defined load spectrum. represents the load case which is same with the The data acquisition system is provided by VXI testing conditions. 3 load cells and 14 EX1629 instrument. In this static strength test, displacement transducers make up the 210 strain channels and 14 displacement instrumentation suite used during testing channels are provided. The strain gages are laid operations. Comparison between the analysis on the surface around the strike damage which results and testing results of load cells and defined by the C scanner. The string displacement transducers is presented in the displacement transducers is place on the ground following sections. position where it defined by a laser position There are 14 testing channels of displacement instrument under the rudder structures. The load transducers along the rudder beam, which are forces and the three reaction forces obtained by used to measure the rudder’s stiffness. A static load cells through the feedback of the control loads analysis of the structure using channels. MSC.Nastran and the loads presented above Loads are applied to the test article with two yielded a maximum displacement of 31.49mm hydraulic actuators attached to the leverage at Point 14. Fig.5 visually depicts the contour of device. Each actuator is individually controlled the X-direction deformation of the analysis with MTS FlexTest 200 digital control system. results. Comparison between the testing data The closed loop system uses both load cell from the displacement transducers and FEA feedback to command hydraulic pressure via numerical analysis results is shown in Fig.6 in servo valve and monitor the LVDT feedback to detail. Analysis results are well accordance with see whether the specimen is safe. The spectrum the test results at all points obviously. is provided by the AeroPro Software and the Simultaneously, the analysis results validates data comes from the aerodynamic calculation that testing data of the points at the root of the which already considered about the jigs weight rudder is nearly zero and points with the same and the installation preload. Fig.3 shows the Y-coordinates have the similar deformation. load spectrum. Internal force results are extracted from the rod element force corresponding with the load cells. 5 FEA and Test results of the Composite Rudder Comparison between the testing data from the FEA(Finite Element Analysis) method is used displacement transducers and FEA numerical to predict the deformation and residue strength analysis results are shown in Fig.7 in detail. of the composite rudder structure after lighting From the FEA results compared with the test stroke. MSC.Nastran and MSC.Patran are used results, all the strains, displacements, the gross as solver and pre/post processor for the virtual load and proportion of the load distribution test. The CQUAD4 shell elements are used to

THE RESIDUAL STRENGTH TEST AND ANALYSIS OF COMPOSITE RUDDER AFTER LIGHTNING STRIKE match well. Fig.8, Fig.9 and Fig.10 present the 8 7 change curves of strain, displacement and load 6 versus load from FEA results. 5 kN 4 3 6 Conclusions 2 1 The static test proved that the composite rudder 0 0 100 200 300 400 500 600 700 can undertake the design limit load considering Time (sec) the environment after light strike. The design arj21_profiles_114% 53: 0% arj21_test 1: start_0% No29:CMD No32:CMD and manufacture process are successful and Fig . 3 . Load spectrum of the two actuators meet the requirement of the airworthiness. After the static test of the composite rudder, a C scan process is carried out again, and it make sure that the damage of the light strike area is no more extend under design limit load. 7 Acknowledgments The authors gratefully acknowledge the support under contract from the Shanghai Aircraft Research Institute, COMAC. Fig.4 Finite element model of the rudder Fig.5. FEA displacement results contour Fig.1. Light strike point and damage shape of the Testing Value Analysis Value composite rudder Undeformed Value 0 Displacement(mm) 4000 Fig.2. Picture of the real static test 2000 2000 Z(mm) Y(mm) 4000 0 Fig.6. Comparison between the analysis and testing results of the displacement 3