Study Of Orthotropic Mechanical Behaviors Of Hot-pressing Weft-knitted Flax/PP Composites And Laminate

Weft-knitted flax fiber fabric reinf orced po lypropylene (P P) com posites is an excellent new environmental m aterials. It com bines the adv antages of flax fiber , PP and weft-knitted fabric. And it has broad application prospects in making sub-bearing structural components for automobiles, aircraft and high-speed trains. So, to establish a tar geted num erical model to p redict its anisotropic el astic-plastic properties is significance.In this paper, macro-and micro-finite element (FE) analysis m ethods are used to study the orthotropic elastic-plastic m echanical behavior of a hot-pressing flax fiber weft knitted fabric reinf orced polypropylene (PP) composite laminate. Based on the study of periodic m icro-structure in th e coil of weft knitted fabrics and the microscopic observation to distortions of th e coil caused by hot pr essing process, a meso-scale f inite ele ment model f or repre sentative v olume elem ent (R VE) is established, in which impregnated yarns are assumed to be isotropic elastic while the matrix is modeled as a n elastoplastic, isotropic solid. Then, by using the m odel, the 3D orthotro pic elas tic-plastic prope rties of the wef t-knitted com posite lam ina are predicted. Lastly, on the basis of a m acro-scale FE model of the composites laminate contained 6 plies, the tensile behavior of [0] 6, [0/90/0] S, [0/90/90] S, [0/45/-45] S, [0/35/-35]S, [0/25/-25]S and [0/15/-15]S are discussed.The results indicate that the m eso- and m acro-FE m odel can predict th e orthotropic elastic-plastic parameters for this kind of weft knitted composites, and can be used as the theo retical and nu merical bas is for the s tructure op timization of laminate and of the strength design of structural parts.