Failure Probability Analysis On The Damaged Composite Laminates Under Tension And Compression Load

Large quantities of composite materials are applied on the C919 aircraft,but China has no independent reliability evaluation system on composites structures.In order to fill the gaps and provide relevant theoratical reserves for the C919 aircraft,this paper use the method of probability theory and determinisyic analysis to analyze the failure risks of the damaged composite laminates under tensile and compressive loads,refering to the NGCAD system.The engineering significance of the reliability anslysis of composite structures is not limited to safety analysis,but also increases the economics of aircraft design and maintenance.The damage type and damage size data in this paper are based on the ststistical results published by the FAA.For the purpose of robust,the representative damage dimensions of different damage types are screened.The damage dimensions from the screen results,are equal to the overrun probability of the normal distribution to the corresponding probability damage size.Use the deterministic method,such as finite element simulation technique,to analyze the influence of holes,cracks and delaminations on the bearing capacity of the laminates.In the process of analysis,it is found that stratified damage under compressive load has greater influnce on the bearing capacity.The current probability analysis theory is highly dependent on the performance function,but it is very difficult to draw a clear performance function from a complex system.In this paper,response surface approximation is uesd to conduct regression equations to fit the performance functions.The regression equations,which take damage types,damage dimensions,capacity reduction and loads into account,can be used in the failure risk analysis.By applying JC method,Laplace method and Monte Carlo Simulation,one can easily get the failure probabilistic results to the regression equations.During the analysis of the failure risks,the fact that the Monte Carlo simulation results are closer to the international standard of 2×10-7,can lead to the conclusion that Monte Carlo simulation is more suitable for the falure probability analysis of complex systems.The work of this paper proves that the combine of the response surface approximation and Monte Carlo simulation can be used to analyze the failure risk of damaged laminates.While this paper can provide guidance for the establishment of China's own reliability assessment system.