Study On Coating Technology And Mechanical Performance Of Pre-directional Warp-knitted Flexible Composite

21st century is a new century for composites. With the development of high performance fiber and high performance resin, it will bring more fresh vigor into fiber reinforced composites. Pre-directional warp-knitted technique and PVC coating technique both are widely used and matured techniques. But the combination of these techniques to exploit pre-directional warp-knitted reinforced flexible composites and membrane structures has not been matured yet.In this thesis, the study was firstly focused on PVC coating process. The orthogonal test method was used to optimize combinations of different processing parameters such as drying time and temperature, material content and coating thickness. The results have shown the influence of the drying time is not obvious, however, the drying temperature, coating thickness and coating material content all affect the mechanical properties of coated samples to some extent. The influence degree from large to small is as follows: drying temperature>material content>coating thickness. And the best combination is: drying temperature 160°C, material content 80%, coating thickness 0.80mm.Based on the coating process obtained above, the tensile, tearing andbursting properties as well as damage modes under different conditions for the coated composites were analyzed. As for the tensile properties, the tensile strength and damage modes are related to testing directions, yarn count, fabric density and the structure of the reinforced yarn. The tearing properties were analyzed by using trapezoid and tongue tearing methods. The results have shown that the tearing strength under the trapezoid tearing condition is about 2-10 times higher than that of the tongue tearing testing. However, the trend of them is similar. The yarns are all broken one by one during the tearing testing, because the accumulation of the yarns is difficult to be done due to coating. For this reason, the tearing curves are rising in sawtooth form. The bursting properties were also analyzed under two testing conditions (bursting tests with spherical plunger and cuspidal plunger). The results have shown that the bursting properties of the composites strongly depend on the bursting conditions and that structural parameters of the warp knitted fabrics have an obvious influence. The comparisons of the mechanical properties for the fabrics before and after coating as well as these coated with PVC and PU resins were also discussed. The results have shown that the coating process has great influence on the mechanical properties, however, the influence of the different resins is not very obvious.It is expected that the results obtained in this thesis will give some valuable reference for the pre-directional warp-knitted flexiblecomposite's design and manufacturing.