Study On Composite Fatigue Properties Of UPVC

As one of the five most widely used composite polymer composites,UPVC has the advantages of high mechanical strength and toughness,low cost,strong plasticity,heat resistance,cold resistance,corrosion resistance of various chemicals and so on,so it is widely used in building materials,packaging,chemical industry,electronics and other industries.It is one of the indispensable polymer materials in modern society,and has a good development prospect.At present,scholars at home and abroad have done a lot of research work on UPVC material modifier,but its mechanical properties have not been fully and effectively studied,the research on its fatigue mechanical properties is less,the research on composite fatigue is less,which greatly affects its application in key structures.The fatigue crack is usually in the state of composite mode,and generally it does not crack in the direction of the original crack when the crack is unstable.Therefore,it is very necessary to study the composite fatigue properties of UPVC,which is of great significance to the fracture resistance,fatigue resistance design,health diagnosis and life prediction of its structure.In this paper,the high cycle fatigue test of UPVC plate with single side crack was carried out by the improved Arcan fixture and MTS809 material machine test loading system under I-II composite mode loading angle,and the general rule of fatigue crack growth of UPVC material under composite mode loading was explored by combining ABAQUS finite element simulation technology.The work of this paper mainly include the following aspects:1.Based on the I-II composite loading test of UPVC plate,the fatigue crack growth of UPVC plate under alternating load is studied:the single side crack growth test of UPVC plate under the I-II composite loading angle of 0°,15°,30°,45°,60°is completed,and the obtained data are processed by seven point polynomial method and fitted with?35?a-Ncurves,da/d N-N curves and da/d N-?35?acurves under different loading angles The change rule of the line is studied and analyzed.2.Based on the test results and ABAQUS finite element simulation,the stress nephogram,displacement nephogram and type I and type II stress intensity factors of UPVC plate with different crack growth length are obtained,and the role of type I and type II stress intensity factors in the crack growth process is discussed by analyzing the fitted?35?K_?40?-?35?a??35?K_?40??40?-?35?aand?35?K^?9?-?35?adata graphs.This paper attempts to use the finite element method to simulate the crack growth path,and verifies the feasibility of simulating the crack growth path by comparing the test results.3.After introducing the concept of composite stress factor,the test and simulation results are fitted to get the I-II composite fatigue crackda/d N-?35?K^?9?curve and lg?7?da/d N?8?-lg?7??35?K^?9??8?curve of UPVC plate.According to Paris formula,the general formu-la of UPVC plate in the stage of stable fatigue crack growt h is obtained.