Study On The Improvement Of Load-life Factor Method Of Composite Material Fatigue Test

Over the past 30 years, the use of advanced composite materials in aircraft primary structures has increased significantly. In 1994, with the Advanced General Aviation Transport Experiments program, the National Aeronautics and Space Administration and the Federal Aviation Administration revitalized the use of composites in general and commercial aviation. Although there are differences between metal and composite about damage mechanics and durability concerns, the certification philosophy for composites must meet the same structural integrity,safety, and durability requirements as that of Metals.Despite the many advantages,composite structural certification becomes challenging due to the lack of experience in large-scale structures, complex interactive failure mechanisms, sensitivity to temperature and moisture,and scatter in the data, especially in fatigue. The overall objective of this study is to ensure the reliability at the same time, considering the economy and test duration, with the improvement of combined load-life factor method, for the load enhancement factor(LEF) and test duration(N0) combination of composite airframe, composite airframe structure provides guidance for argument.This article mainly has carried on the research work of the following several aspects:(1) overview of composite material airframe structure durability test, introduces its building blocks of testing method and the composite material scatter analysis method, and introduces the existing composite airframe structure durability test methods —life factor method, load enhancement factor method and the ultimate strength method in detail, the most important thing is to deduce the improvement of load-life factor method, and LEF and N0 combination of composite materials,ensuring the reliability and confidence of the same premise and effectively shortening the time of the full-scale test time of composite airframe.(2) study on the fatigue behavior of CCF300/BA9916-II composite laminates with the layer paving way of [45/0/-45/90]s under the effect of pulling loads and use the improvement of load-life factor method in the paper, get the composite laminates shape parameters of the fatigue life and residual strength under B-Basis, then get theLEF and N0 combination of composite materials. And comparison of the composite statistical results and the experimental results, which can prove the correctness of the improvement of load-life factor method. The method analyze of the composite dispersion by using the improved joint Weibull distribution, which simplifies the process of solving the LEF and N0 combination of composite materials.(3) study on the fatigue behavior of the layer paving way as[45/-45/0/0/-45/90/0/90/45/0]s of T300/BMP316 composite laminates of new type(with hole and without hole) under the effect of pulling loads and use the improvement of load-life factor method to get the LEF and N0 combination of composite materials, which can combined effect of test pieces and aperture that parts of laminated to LEF and N0 combination of composite.