Structural warp knit sheet and laminate thereof

Abstract

The structural warp knit sheet provided by this invention is a warp knit sheet for spars or stringers which comprises: a warp knit structure constituted of chain-stitch structures configured of ground knitting yarns; longitudinal insertion yarns that have been inserted in the longitudinal direction into the warp knit structure, the longitudinal insertion yarns being continuous carbon fiber yarns; and transverse insertion yarns that have been inserted in directions along which the transverse insertion yarns shuttle between the adjacent chain-stitch structures, the chain-stitch structures having been united by means of the transverse insertion yarns. The longitudinal insertion yarns are carbon fiber yarns which each is composed of 12,000-50,000 filaments and has a tensile strength of 4 GPa or higher, a tensile modulus of 220-450 GPa, and a drape value of 4-22.

1 . A structural warp knit sheet to serve as a warp knit sheet for spars and stringers, comprising a warp knit structure constituted of chain-stitch structures of ground knitting yarns, continuous carbon fiber yarns inserted into the warp knit structure in the longitudinal direction as longitudinal insertion yarns, and transverse insertion yarns inserted in directions along which they shuttle between the adjacent chain-stitch structures to unite the chain-stitch structures, the longitudinal insertion yarns being carbon fiber yarns each including 12,000-50,000 filaments and having a tensile strength of 4 GPa or higher, a tensile modulus of 220-450 GPa, and a drape value of 4-22, and the longitudinal insertion yarns each being able to move independently of the adjacent yarns and able to be arranged along the shape of a curved plane. 
     
     
         2 . The structural warp knit sheet according to  claim 1 , wherein the carbon fiber yarns have a maximum movable distance of 0.5 to 10 mm and wherein, when the structural warp knit sheet is placed over a hemisphere having a radius of 0.1 m, the carbon fiber yarns can be arranged along the shape of the curved plane of the hemisphere. 
     
     
         3 . The structural warp knit sheet according to  claim 1 , wherein at least either of the ground knitting yarns and the transverse insertion yarns are crimped yarns or covering yarns. 
     
     
         4 . A warp knit sheet laminate comprising structural warp knit sheets as set forth in  claim 1 , their number being 50 to 300 in the thickest part, the structural warp knit sheets being partially bonded or stitched together, the carbon fiber yarns being arranged along the shape of a curved plane having a minimum radius of curvature of 0.1 to 10 m in its curved part, and at least 50 weight % of the structural warp knit sheets in the warp knit sheet laminate are arranged so that the lengthwise direction of the warp knit sheet laminate and the fiber-axis direction of the longitudinal insertion yarns substantially coincide. 
     
     
         5 . The warp knit sheet laminate according to  claim 4 , wherein the laminated structural warp knit sheets have a binder at least on their surfaces and the partial bonding between laminated structural warp knit sheets is achieved by the binder.