Study On The Stress Relaxation And Fatigue Properties Of The Tenting Flexble Composites

As a newly arisen material, flexible composites have been widely used in many fields. In the present market, the reinforced parts of the flexible composites are mainly woven fabric and warp-knitted bi-axial fabric. In contrast to the woven fabric, warp-knitted bi-axial fabric has better tensile strength, elastic modulus, tearing resistance and lower cost. Therefore, the using percentage of warp-knitted fabric being the reinforcement part of the composites has been raised as well as its application.When flexible composites are used as advertising banner, home natatorium and so on, it will inevitably suffer various outside forces and bring the stress relaxation and fatigue effect which will do harm to the properties and its life. In this thesis, we mainly studied on the stress relaxation and fatigue performance of the flexible composites whose reinforcements are warp-knitted bi-axial fabric and woven fabric. They are both made of PET and utilize calender to make the fabric and PVC film become composites.There are all together five different samples in this thesis. Excepttesting the mass per unit area, density, thickness and tensile strength, we stress relaxation and fatigue performances were mainly tested. Based on the data, comparison and analysis are necessary to come out with the conclusions.After the testing, the drawing of the corresponding curves helped to build the mechanics models for simulation. According to the simulation results, the use life of the materials can be forecast. The testing results of the mechanical performances after the stress relaxation and fatigue experiments were used to evaluate the performance decline.Through the stress relaxation research, the mechanics models were established to simulate the stress relaxation of flexible composites through which a comparison of different models to see their simulation adaptability can be made. Fatigue experiments validated that the fatigue curve of flexible composites follows the S-N theory and thus the repetition times of fatigue load before the material was tore can be forecasted. Also through the fatigue test the conclusion would come out that the mechanical performance of flexible composites would decline if repeated outside forces act on it.The conclusions have been got and the work have been done in the thesis will do a great help to understand the properties of the warp-knitted bi-axial and woven flexible composites. For the practical production, they also contribute a certain reference value.In this thesis, however there are still some shortages that should be improved in the future. At the end of this thesis a sum-up were made and foresaw the developing prospects of flexible composites.Written by Guo Yu (Textile Engineering) Supervised by Shen Wei...