Properties Of Biaxial Weft Knitted Thermoplastic Composites

Fabric composite is a kind of advanced composite reinforced by fabric preformed. Traditional textile techniques such as weave,intertexture and knit have been used abroad in the field of manufacturing and studying composite. Contrasted with the thermoset composite, the superior specialties of thermoplastic composites are perfect tenacity and impact resistance, stable preheating materials, short produce periods, being able to be reproduced and recovered and so on. The knitted techniques, hot-press technology and tensile properties of biaxial weft knitted thermoplastic composites are investigated in this article.Biaxial wefts knitted fabrics with reinforce roving and polypropylene filaments are preformed in improved fiat knitting machine. This kind of composite is attracting more and more interests due to its outstanding mechanical properties and competitive production cost, it can improve impregnation of high molecular weight polymer, make formation and processing adjust easy, facilitate the proportion adjust and control of reinforced fibers and resin.By experimental work and theoretical analysis, the author investigated the principle of knitting biaxial wefts knitted fabrics and knittability on flat knitting machine, This part analyzes the influence of yarn tension, taking down force, pulling down depth in detail. The key technique and parameters for the shaping of biaxial wefts knitted fabrics was explored.We analyze the process of thermoplastic composites impregnation in hot pressing machine theoretically. By the experience we confirmed the fight parameter of the hot-press temperature, intensity of pressure, retentive time, the method of lower temperature etc. and discussed how these parameter influenced the biaxial wefts knitted thermoplastic composite. The crystallinity properties of Polypropylene and reinforce fiber/Polypropylene are investigated by using DSC.The tensile properties of composite were investigated experimentally. On the basis of test results, we analyze some main factors influencing stress-strain curve, ultimate tensile strength and initial modulus of specimens, failure behaviors of the specimens are also studied. It comes a conclusion that with the insert yarns the mechanical properties of the composite has improved greatly and it takes an important role to the axial mechanical properties of composite. By changing the kinds and content of insert yarns, it can obtain different tensile properties in the axial. With different stacking configuration, such as [0/90], [0/-45/45/90], it can improve the anisotropy of mechanics properties...