Study On Equivalent Simulation Method And Residual Strength Of Laminated Plate With Delamination Damage

Fiber reinforced resin matrix composites as a repres entative of advanced composite materials has been widely applied in panel structure of aircraft wing by its superior mechanical properties. But in preparation, assembly and service process of composite material structure, due to a series of uncertain facto rs, invisible delamination damage may be occured,as a result, the mechanical performance of the whole structure will be affected, even the safety of the aircraft structure.So this problem is often to be faced and urgent to be solved. In this paper, equivalent simulation method will be studied according to different damage detection results, and the research on the residual strength of delaminated laminated plate via test method combined with FEM simulation method will be carried out.First of all,Delamination damage internal morphology of specimens were obtained through the ultrasonic testing method. Secondly, its damage contour were obtained through the image processing technology.Then, from the point of mathematical, the optimal characteristi c parameters for equivalent simulation were calculated by fitting contour using several different fitting methods via MAT LAB and assessing the accuracy. Besides, the fitting operation interface were developed to applied conveniently through MAT LAB.For typical delaminated composite laminates, finite element analysis model were established based on the theory of cohesion model through ABAQUS. By developing the corresponding USEFLD subroutines, the simulation of layer board’s progressive failure process were realized, the failure mode and the prediction of residual strength were predicted. Meanwhile, aiming at the condition of the engineering scan only indicated the damage length, the sensitivity studies were conducted on the delamination shape, the length of the axis value, angle and position in the thickness of the typical structure. The influence law of the residual strength of laminated plate were revealed under different damage characteristic parameters and the equivalent simulation method were summarized that adapt to its failure mode. In addition, through a lot of simulation, the effect of boundary on the residual strength of the effect were discussed, so as to seek the optimal size of modeling.An experimental study were carried out for specimens contain ing preset delaminated injuries which conform to the residual strength test standard. Using PTFE film to achieve the preset delamination damage, the failure modes, failure load and residual compressive strength were obtained through conducting compression residual strength test on specimens after passing the scan test. T he error were in the permitted range by comparing the test results with FEM simulation results and thus the validity of the finite element model were verified.