Reinforcing mat having thermally fused stitching

Abstract

A mat useful for reinforcing composite materials is made up of at least first and second sets of fibers, the first set of fibers laid as a ply in spaced apart parallel relationship in the direction of construction and the second set laid as a ply in spaced apart parallel relationship perpendicular to the direction of construction. These fibers define interstices, into which a continuous filament is knitted to provide stability. The filament has a core portion and a sheath portion, the sheath portion having a lower melting point than the core portion. The sheath portion is thermally fusible to form a plurality of closed loops in which the respective sets of fibers are entrapped. The fibers are glass or glass rovings and the filament is a polyester, the core portion being a high-viscosity poly(ethylene terephthalate) and the sheath portion being a low-viscosity poly(ethylene terephthalate).

What is claimed is:  
     
         1 . A mat for reinforcing having a direction of construction, comprising: 
 a first set of fibers laid as a ply in spaced apart parallel relationship in the direction of construction;    a second set of fibers laid as a ply in spaced apart parallel relationship perpendicular to the direction of construction, the position of the second set of fibers adjacent to to the first set of fibers defining a plurality of interstices;    a continuous filament knitted into the interstices to provide stability;    wherein the filament has a core portion and a sheath portion, the sheath portion having a melting point that is lower than a melting point of the core portion, such that sheath portion is thermally fusible to form a plurality of closed loops in which the first and second sets of fibers are entrapped.    
     
     
         2 . The reinforcing mat of  claim 1 , further comprising: 
 a third set of fibers, laid as a ply adjacent to said first and said second sets, the third set of fibers laid in spaced apart parallel relationship oblique to the direction of construction and oblique to the direction of the second set of fibers, the position of the third set of fibers relative to the first and second sets of fibers further defining interstices.    
     
     
         3 . The reinforcing mat of  claim 2 , further comprising: 
 a fourth set of fibers, laid as a ply adjacent to said first and said second sets with the third set, the fourth set of fibers laid in spaced apart parallel relationship oblique to the first, second and third sets, the position of the fourth set of fibers relative to the first, second and third sets of fibers further defining interstices.    
     
     
         4 . The reinforcing mat of  claim 1 , wherein the first and second sets of fibers are glass fibers.  
     
     
         5 . The reinforcing mat of  claim 1 , wherein the first and second sets of fibers are glass rovings.  
     
     
         6 . The reinforcing mat of claim, wherein the filament comprises a high-viscosity polyester core portion and a low-viscosity polyester sheath portion.  
     
     
         7 . The reinforcing mat of  claim 6 , wherein the polyester is a poly(ethylene terephthalate).  
     
     
         8 . The reinforcing mat of  claim 6  wherein the filament is a mono-filament construction.  
     
     
         9 . The reinforcing mat of  claim 6 , wherein the filament is a multi-filament construction.  
     
     
         10 . The reinforcing mat of  claim 2  wherein the third set of fibers is laid at an angle of 45E relative to each of the first and second sets of fibers.  
     
     
         11 . The reinforcing mat of  claim 3  wherein the fourth set of fibers is laid at an angle of 45E relative to each of the first and second sets of fibers and is laid perpendicular to the third set of fibers.  
     
     
         12 . A mat for reinforcing having a direction of construction, comprising: 
 a first set of fibers laid as a ply in spaced apart parallel relationship in the direction of construction;    a second set of fibers laid as a ply in spaced apart parallel relationship perpendicular to the direction of construction, the position of the second set of fibers adjacent to the first set of fibers defining a plurality of interstices;    a third set of fibers, laid as a ply adjacent to said first and said second sets, the third set of fibers laid in spaced apart parallel relationship oblique to the direction of construction and oblique to the direction of the second set of fibers, the position of the third set of fibers relative to the first and second sets of fibers further defining interstices.    a fourth set of fibers, laid as a ply adjacent to said first and said second sets with the third set, the fourth set of fibers laid in spaced apart parallel relationship oblique to the first, second and third sets, the position of the fourth set of fibers relative to the first, second and third sets of fibers further defining interstices.    a continuous filament knitted into the interstices to provide stability;    the filament having a core portion and a sheath portion, the sheath portion having a melting point that is lower than a melting point of the core portion, such that sheath portion is thermally fusible to form a plurality of closed loops in which the respective sets of fibers are entrapped;    the third set of fibers being laid at an angle of 45E relative to each of the first and second sets of fibers;    the fourth set of fibers being laid at an angle of 45E relative to each of the first and second sets of fibers and is laid perpendicular to the third set of fibers;    the respective sets of fibers comprising glass; and    the filament comprising a high-viscosity poly(ethylene terephthalate) core portion and a low-viscosity poly(ethylene terephthalate) sheath portion.