Stitch-reinforced sandwich panel and method of making same

• US 6,187,411 B1
• Filed: 10/03/1997
• Issued: 02/13/2001
• Est. Priority Date: 10/04/1996
• Status: Expired due to Term

• Current Assignee: Mcdonnell Douglas Corporation (The Boeing Co.)
• Original Assignee: The Boeing Co.
• Inventors: Palmer, Raymond J.
• Primary Examiner(s): Ahmad, Nasser
• Application Number:
  US08/943,950
• Time in Patent Office: 1,229 Days
• Field of Search: 428/99, 428/102, 428/120, 428/318.4, 428/317.9, 428/318.6, 428/316.6, 428/104, 416/229.R, 416/230
• US Class Current: 428/102
• CPC Class Codes: B29C 70/543 Fixing the position or configuration of fibrous reinforcements before or during moulding for non-woven fabrics D04H3/08
• CPC Class Codes: B29C 70/865 completely encapsulated
• CPC Class Codes: B32B 2250/03 3 layers
• CPC Class Codes: B32B 2260/021 Fibrous or filamentary layer
• CPC Class Codes: B32B 2260/046 Synthetic resin
• CPC Class Codes: B32B 2262/0261 Polyamide fibres
• CPC Class Codes: B32B 2262/0269 Aromatic polyamide fibres
• CPC Class Codes: B32B 2262/0276 Polyester fibres
• CPC Class Codes: B32B 2262/101 Glass fibres
• CPC Class Codes: B32B 2262/106 Carbon fibres, e.g. graphite fibres
• CPC Class Codes: B32B 2266/0278 Polyurethane
• CPC Class Codes: B32B 2305/186 Knitted fabrics
• CPC Class Codes: B32B 2307/50 having particular mechanical properties
• CPC Class Codes: B32B 2307/54 Yield strength; Tensile strength
• CPC Class Codes: B32B 2307/546 Flexural strength; Flexion stiffness
• CPC Class Codes: B32B 2307/558 Impact strength, toughness
• CPC Class Codes: B32B 2307/72 Density
• CPC Class Codes: B32B 2315/085 Glass fiber cloth or fabric
• CPC Class Codes: B32B 2605/00 Vehicles
• CPC Class Codes: B32B 2605/08 Cars
• CPC Class Codes: B32B 2605/12 : Ships
• CPC Class Codes: B32B 2607/00 : Walls, panels
• CPC Class Codes: B32B 3/10 : characterised by a discontinuous layer, i.e. formed of separate pieces of material
• CPC Class Codes: B32B 5/024 : Woven fabric
• CPC Class Codes: B32B 5/06 : characterised by a fibrous or filamentary layer mechanically connected, e.g. by needling to another layer, e.g. of fibres, of paper
• CPC Class Codes: B32B 5/18 : characterised by features of a layer of foamed material
• CPC Class Codes: B32B 5/22 : characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed layer formed of natural mineral fibres or particles next to a foam layer B32B19/047, next to a layer made of particles B32B19/048, or next to a fibrous or filamentary layer B32B19/06; paper layer or cardboard layer next to a paper layer or cardboard layer B32B29/005, next to a foam layer B32B29/007, next to a fibrous or filamentary layer B32B29/02, or next to a particulate layer B32B29/04
• CPC Class Codes: B32B 5/245 : another layer next to it being a foam layer
• CPC Class Codes: B32B 7/05 : the layers not being connected over the whole surface, e.g. discontinuous connection or patterned connection using interposed adhesives or bonding materials applied in spaced arrangements B32B7/14
• CPC Class Codes: B32B 7/12 : using interposed adhesives or interposed materials with bonding properties
• CPC Class Codes: Y10T 428/24008 : including fastener for attaching to external surface
• CPC Class Codes: Y10T 428/24033 : including stitching and discrete fastener[s], coating or bond
• CPC Class Codes: Y10T 428/2405 : Coating, impregnation, or bond in stitching zone only
• CPC Class Codes: Y10T 428/24182 : Inward from edge of web or sheet
• CPC Class Codes: Y10T 428/249981 : Plural void-containing components
• CPC Class Codes: Y10T 428/249986 : Void-containing component contains also a solid fiber or solid particle
• CPC Class Codes: Y10T 428/249987 : With nonvoid component of specified composition
• CPC Class Codes: Y10T 428/249988 : Of about the same composition as, and adjacent to, the void-containing component

Abstract

A stitch-reinforced sandwich panel with improved flatwise tensile strength, improved skin to core peel strength, and substantially reduced damage propagation from impact includes a relatively non-compressible foam core, a dry reinforcing layer of fibers placed on each of the opposite faces of the foam core; and high strength thread stitched with a high density of stitches over the entire panel through each of the reinforcing layers and the foam core. The skins are then impregnated with a resin system to complete the structure.

Claims

1. A stitch-reinforced sandwich panel, comprising:

a foam core having a pair of opposite first and second faces;

first and second skins of fiber reinforcing material respectively covering the first and second faces of the foam core; and

a reinforcing thread stitched through each of the skins and through the foam core to form stitches arranged in a generally regular pattern over substantially the entire faces of the foam core, the stitching joining the skins and the core together to form a stitch-reinforced sandwich panel;

wherein the foam core is formed of a plurality of discrete foam pieces that are spaced apart to form intervening spaces therebetween, and the first and second skins are in direct contact with each other and are stitched directly to each other in the intervening spaces between the discrete foam pieces.

2. The stitch-reinforced sandwich panel of claim 1, wherein the skins comprise layers of non-matrix-impregnated fiber material.

3. The stitch-reinforced sandwich panel of claim 1, wherein each skin comprises a plurality of layers of non-matrix impregnated fiber material.

4. The stitch-reinforced sandwich panel of claim 3, wherein the layers of each skin are knit together to form a warp knit fabric.