Micro-defect Of The RTM/textile Composites Detect Nonlinear Evaluation Method Research

Due to the excellent characteristics of the composite material more widely used.RTM is a mold closing low-cost manufacturing technology between SMC process andhand lay-up process.Combined with textile technology, can get components withlow-cost, high-performance and complex internal structure. In recent years, has beenwidely used in aviation, aerospace, nuclear energy and other fields. However, Due to theinfluence of the preparation process, the environment, the preform, Makes this kind ofproduct is easy to exist within the dense pore. The pores exist severely reduces themechanical performance and fatigue life of composite materials.So according to practical needs and research status, in this paper the RTM/textilecomposites is the detection object, the nonlinear ultrasonic detect experiments isperformed in the RTM/textile composites, which have different pore content. Bymeasuring the nonlinear characteristic parameters, the porosity of RTM/textilecomposite materials can be evaluated.First of all, starting from a solid one-dimensional longitudinal wave nonlinearwave equation. some important ultrasound nonlinear effects are introduced, pushed to ahigher order nonlinear coefficient. And point out that The relative ultrasonic nonlinearparameters can be used as the characteristic parameters to evaluate the porosity ofRTM/textile composite.Secondly, according to the propagation characteristics of the acoustic wave, usingF-scan imaging detection technology evaluate the RTM/textile composite panels.And then，depending on the characteristics of the selected parameters, based on afinite amplitude test method, design a nonlinear test system. Using this system detectthe RTM/textile composite. Observed second-order and third-order the relativenonlinear coefficient changes.Finally, through the commercial Ritec5000SNAP nonlinear instrument to verifythe experiment. Make the experiment more reliable. After detection, we usemetallographic micrograph observed internal void content to verify nonlinear ultrasoundexperiments results.The results show that: the existence of a good linear relationship between the relatively non-linear coefficient changes and trial block porosity. Can be used to RTM/textile composite porosity ultrasound evaluation. the build system and commercial Ritec5000SNAP nonlinear instrument system can get the same trend in the porosity of thetest Sample. That build system can satisfy the nonlinear ultrasonic measurementrequirements, the measurement results are accurate and reliable. But the test system stillhave many uncontrollable nonlinear factors. In order to accurately quantitative researchthe nonlinear characteristics of the materials, Urgent need to optimize and improve themeasurement system, And preparation of a variety of pore content of the sample,quantitative evaluation of their porosity.