Process for making a perforated rigid sheet material for sound absorbing composite cellular structure

• US 4,390,584 A
• Filed: 01/21/1981
• Issued: 06/28/1983
• Est. Priority Date: 04/18/1980
• Status: Expired due to Term

• Current Assignee: Aerospatiale Societe Nationale Industrielle
• Original Assignee: Aerospatiale Societe Nationale Industrielle
• Inventors: Briens, Guy
• Primary Examiner(s): Woo, Jay H.
• Application Number:
  US06/226,932
• Time in Patent Office: 888 Days
• Field of Search: 264/103, 264/24.5, 264/257, 264/324, 264/45.6, 264/45.3, 428/116, 428/109, 428/107, 428/113, 428/247, 428/245
• US Class Current: 428/116
• CPC Class Codes: B29D 24/005 the structure having joined ribs, e.g. honeycomb
• CPC Class Codes: B32B 2262/106 Carbon fibres, e.g. graphite fibres
• CPC Class Codes: B32B 2305/38 Meshes, lattices or nets
• CPC Class Codes: B32B 2307/10 having particular acoustical properties
• CPC Class Codes: B32B 3/12 characterised by a layer of regularly- arranged cells, e.g. a honeycomb structure
• CPC Class Codes: B32B 3/26 characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids foam layer B32B5/18; layer of synthetic resin characterised by fillers that create voids or cavities B32B27/205; characterised by an apertured layer
• CPC Class Codes: E04B 1/86 slab-shaped
• CPC Class Codes: E04B 2001/748 Honeycomb materials
• CPC Class Codes: G10K 11/172 using resonance effects
• CPC Class Codes: Y10T 428/24149 Honeycomb-like

Abstract

A composite structure for absorbing sound energy, comprising an outer porous layer covering a cellular layer, wherein said porous layer is made by forming a supple loose fabric from slivers each constituted by a plurality of relatively free mineral or synthetic fibres, substantially parallel to one another and shaping said supple fabric to its final form and rendering it rigid by means of a hardenable resin, while being subjected to pressure so as to become a thin, rigid lattice, with wide crossed lines, virtually uniformly smooth on at least its face opposite said cellular layer.

Claims

1. A process for making a light, perforated, electrically conducting rigid sheet material suitable for use as the outer surface in a sound absorbing composite cellular structure comprising the steps of:

providing a supple loosely woven fabric comprising a plurality of spaced parallel warp slivers and a plurality of spaced parallel transverse weft slivers interlaced therewith, said warp and weft slivers defining openings corresponding to a porosity greater than that desired in said rigid sheet,

each of said slivers comprising a plurality of substantially straight parallel and unconnected fibers, and a pair of electrically conducting wires arranged respectively at the opposite margins of said sliver, the marginal wires in said slivers being electrically interconnected to form an electrically conducting grid;

impregnating said fabric with a hardenable resin;

applying controlled pressure to opposite faces of said impregnated fabric to create lateral expansion of said slivers sufficient to reduce the porosity to that desired in said sheet; and

hardening said resin while maintaining said pressure, to produce a thin rigid electrically conducting sheet having said desired porosity.

2. The process of claim 1 wherein said pressure is applied by means which produces a substantially uniformly smooth surface on at least one face of said sheet.

3. The process of claim 1 wherein the porosity of said supple fabric is about 25-35% and the porosity of said rigid sheet is about 5-15%.

4. The process of claim 1 wherein, in said supple fabric, said warp slivers and said weft slivers are positioned at right angles to each other and define square openings whose sides have a length substantially equal to the width of said slivers.

5. The process of claim 1 wherein said fibers comprise carbon filaments.

6. The process of claim 5 wherein said warp and weft slivers in said supple fabric are about 2 mm wide and define square openings having sides about 2 mm long.

7. The process of claim 1 wherein said wires are made of bronze.

8. A perforated rigid sheet material made in accordance with the process of claim 1.