Study On Mechanical Characteristics Of Fiber-Reinforced Rubber At Different Temperatures

The mechanical characteristics of vulcanizate rubber and nylon fiber cord and their composites can be significantly influenced by temperature. To study on interface of fiber cord/rubber composite and its macro-mechanics is of more important significance to analyzing the failure and damage of transmitting belt for building and tyre. The heat is one of reasons for which mechanical properties of fiber cord/rubber composite decrease and is failure. Heat comes from two sources:one is a transmitted heat such as high temperature belt which is subjected to out heat; another is a generating heat such as the tire with high speed which can generate heat itself. Although the heat source is different, it has same effect on fiber or rubber material. Recently, with the rapid improvement of experiment and numerical analysis, study on fiber rubber composite interface characteristics under different temperature is possible. Study on mechanical characteristic of fiber cord/rubber composite under different temperatures was investigated in this paper, mainly as follows:1. Experiment of uniaxial tension at different temperates of vulcanizate rubber and nylon fiber are carried out. Based on this, the constitutive relation of vulcanizate rubber and nylon cord is studied. According to experimental results, the load-displacement relation, stress-strain relation are set up according to the Mooney-Rivlin model and Yoeh model, the parameters of C1, C2, C3are deduced which provide theory base for the later research.2. The thermal expand of material may affect its mechanical performance especially for2-phase or multi-phase materials. In the paper, the thermal expand performance of vulcanizate rubber and nylon fiber cord is researched. Experimental results showed that the thermal expanding coefficient increases with temperature increasing, but the nylon fiber demonstrates negative values with V shape. 3. The pulling-out experiment of single fiber cord rubber composite is made to analyze the mechanical performances and interfacial mechanical performances, the load-displacement relations at different temperatures are obtained. The mean shear stress, interfacial cracking energy is calculated to roughly evaluate interfacial characteristics.4. Observed the surface of fiber pulled-out with SEM, we can find that three failure modes occurred, that is, at low temperature, the interfacial cracking is adhesive failure between fiber and rubber matrix; at middle temperature, in addition to adhesive failure, the matrix damage near the interface is found; at high temperature, the cracking occurred totally in matrix. It is showed that the strength of matrix is less than the interface adhesive force.5. Base on the above three modes, three interface failure model are built to describe the interfacial cracking process and cracking rules at different temperatures. Combined with above method and using interfacial unit layer and technology of "living" or "dieing" for unit, the problem of mesh aberration caused by large deformation of rubber material can be solved in simulating fiber pull-out. According to above teclinology, an effective method for analyzing interfacial cracking of composite with large deformation was given.6. Using this teclinology, the interface, load pull-out and stress field variation of single fiber coed-reinfoced vulcanizate at different temperatures are totally analyzed and predict by FEA. The results indicate that the computing data of pulling-out load have a good agreement with experimental results.7. The dimension effects are considered in FEA. Through changing the matrix diameter and fiber embeded depth, the load-displacement relation, interfacial axial stress field and shearing stress field are observed in the results of FEA. The results show that there is a sharp local stress concentration in interface and so on. All of these will provide a useful support for composites structure design and research in future.