Study On Mechanical Properties Of Multi-axial Carbon Warp-Knitted Reinforced Composite Materials With Glass-fiber Binder Yarn

Warp-knitted axial fabrics not only take advantages of high-strength and high-modulus of high-performance yarns, but also make full use of the deformability of knitted loop. Due to their excellent moldability, inherent drapability, good impact resistance and energy-absorbing properties, cheaper production cost and more simple technological process than other textile reinforced structures, multi-axial warp-knitted fabrics have been widely studied and used, became the most ideal textile reinforced structures. Recently multi-axial warp-knitted fabrics reinforced composite materials enhanced by high-performance carbon fiber have been extensively used in aviation,spaceflight,military,sport goods fields and ect. because of their light -weight,high-spec fic strength and high-specific modulus.In the knitting of multi-axial warp-knitted fabrics, the functions of binder yarn are to fix inlay yarn, avoid fiber slipping in layers and interlayer. But there're study show that the material and stitch structure of binder yarn can greatly affect the properties of multi-axial enforenced structure material by affecting reinforcing fiber. Nowadays people usually use polyester as binder yarn, but actually glass-fiber have higher strength and modulus than polyester, as well as excellent properties of heat-resistant and aging resistance. Compare to polyester, glass-fiber has better binding performance with resin, which could increase the impregnation property of resin in fabric, and improve interlaminar properties of composite materials.The main purposes of this study are to improve mechanical properties of composite materials by studying matrerials and stitch structures of binder yarn for adapting to higher request of materials in aviation,spaceflight,military ect. fields, and expanding application range of glass-fiber. So this paper studied the porosity, tensile properties, bending properties and impact properties in various aspects of±45°biaxial carbon warp-knitted reinforced composite materials with glass-fiber binder yarn. In order to confirm the knittability of glass-fiber, the tensible properties of glass-fiber binder yarn and polyester binder yarn before and after knitting were compared. We tested and compared the tensile properties in directions of warp,weft and 45 of four types of biaxial carbon warp-knitted fabrics including polyester/chain,glass-fiber/chain, polyester/tricot,and glass-fiber/tricot, finished the composite molding of reinforced fabrics and epoxy resin. We used burning method to test the porosities of all composites, tested the tensile properties in directions of warp,weft and 45°, warp bending properties and warp impact properties of composites, and compared test data, observed failure simples, analyzed the failure models, studied the effect of glass-fiber binder yarn and its stitch structures on mechanical properties of composites.The results indicate that due to glass-fiber's stiffness and easy to decoherence, the fabrics with glass-fiber binder yarn have lower tensile strength in the warp tensile testing of±45°biaxial carbon warp-knitted fabric.The porosities of all composites rank from low to high are: glass-fiber/chain,polyester/chain,glass-fiber/tricot,polyester/tricot. The porosities of composites with glass-fiber binder yarn are lower than composites with polyester binder yarn.The more layers are,the lower the porosities are. Based on analysis of the test data and failure models of tensile properties,bending properties and impact properties of composites, we obtained the following conclusion:using glass-fiber to replace polyester as binder yarn can increase the mechanical properties of composites in certain extent by improving composites'interlaminar properties. When the binder yarns are the same, tricot stitch composites has better mechanical properties than chain stitch.