GB2272749A

GB2272749A - Acoustic and thermal insulation panel, e.g. for aircraft

Info

Publication number: GB2272749A
Application number: GB9323962A
Authority: GB
Inventors: Bruce Raymond Wilson
Original assignee: INSOLEQ Ltd
Current assignee: INSOLEQ Ltd
Priority date: 1992-11-21
Filing date: 1993-11-22
Publication date: 1994-05-25
Anticipated expiration: 2013-11-22
Also published as: GB2272749B; GB9323962D0

Abstract

Acoustic and thermal insulation elements (10), particularly for use in aircraft, are formed from semi-rigid foamed polymeric material (preferably polyimide foam) with channels therein forming ducts. The panels may be formed from layers of foam material and ducts (12) may be formed in a central layer (18) sandwiched between outer layers (14, 16). The outer surface of the panel are covered and the internal surfaces of the ducts are lined with non-porous material, such as fibre reinforced PVF film. The panels can be fabricated to relatively precise dimensions with integral ducting, and will maintain their shape, thickness and exterior dimensions; they may be used in aircraft such that the ducts serve for air-conditioning. <IMAGE>

Description

"Improvements in Acoustic and Thermal Insulation for Aircraft" The present invention relates to acoustic and thermal insulation methods and materials, particularly for aircraft cabins.

Conventionally, acoustic and thermal insulation in the walls of aircraft cabins has been provided by low density glass fibre enclosed in "bags" of heat and flame resistant material to form blankets which are enclosed between the skin of the aircraft and the interior cabin panels, and which fit around stringers, frames or other obstacles. The use of such materials has a number of disadvantages. Firstly, the blankets themselves have no structural rigidity, making them difficult to handle and to fit precisely. Secondly, the loose glass fibre material enclosed in the bags tends to migrate to the bottoms of the bags over time ("shakedown"). Thirdly, there is normally a requirement for ducts of various types, such as air conditioning ducts, to extend through the insulating layer from the cabin floor to the ceiling.This requires conduits to extend through the glass fibre filling of the blankets. Such conduits are typically formed from coiled wire and polymeric material, and add significantly to the weight of the assembly.

It is an object of the present invention to provide an improved approach to the acoustic and thermal insulation of aircraft cabins, allowing greater precision and consistency with a reduced weight penalty.

In accordance with the invention, there is provided an insulating element comprising a panel of predetermined shape formed from an acoustically and thermally insulating foamed polymeric material which is at least semi-rigid, the panel having at least one channel defining a duct extending at least partially therethrough.

Preferably, the exterior surfaces of said panel are covered and sealed around its periphery by a layer of non-porous material.

Preferably, the foamed polymeric material is an opencelled polyimide foam.

Preferably also, said at least one channel is lined by a layer of non-porous, non-metallic material so as to be sealed from the foam material of the panel.

Preferably also, the non-porous material covering the panel and/or lining the channel is heat and flame resistant.

Preferably also, the non-porous material covering the panel and/or lining the channel is a lightweight, fibre reinforced PVF film.

Alternatively, the non-porous material lining the channel is glass, aramid or ceramic fibre reinforced, resin impregnated, laminated material, most preferably a modified phenolic resin or similar. As a further alternative, the lining may be polymeric material applied as film, or by brush or spray methods.

Preferably also, the panel comprises first and second outer layers of foamed polymeric material and at least one inner layer sandwiched between said outer layers, said at least one channel being formed by cutting said inner layer.

Preferably, the panel further includes at least one additional layer of material of higher density than said outer layers.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a side view of a sound proofing element in accordance with the invention; Fig. 2 is a top end view of the element of Fig. 1; and Fig. 3 is an isometric view of a panel forming the element of Figs. 1 and 2 with an outer layer folded back to show the interior channels thereof.

The Drawings show an example of an acoustically and thermally insulating panel 10 for use in an aircraft cabin, with a channel 12 defining a Y-shaped duct therethrough. The configuration of the duct path(s) may vary widely according to need, and the invention is in no way limited by the shape, number or arrangement of the channels, the present Y-shaped channel being given by way of example only.

The panel 10 is formed from a foamed polymeric material having acoustically insulating, thermally insulating and heat and flame resistance properties as specified or required for aircraft sound-proofing applications.

Preferably, the material is an open-celled lightweight polyimide foam which is at least semi-rigid so that it can be accurately cut and formed to a predetermined shape or configuration. A suitable material is "Willmid" (Registered Trade Mark) from Illbruck GmbH.

The panel 10 may be generally planar and be bent in use to conform to the curvature of the aircraft fuselage, or may be pre-formed with a suitable curvature.

As seen in the drawings, a Y-shaped channel 12 extends through the interior of the panel 10 between the upper and lower peripheral edges thereof. In this example the panel 10 is formed from inner and outer exterior layers of foam 14 and 16, and inner layer 18 sandwiched therebetween. The channel 12 is formed by cutting the inner layer 18 prior to bonding the layers together using a suitable adhesive.

The channel 12 will typically provide an airconditioning duct, in which case it must be sealed from the surrounding foam so that no air shall permeate from the duct into the foam or escape from the panel itself into any adjacent airspace, and must be capable of meeting pressure test requirements. Means for sealing the duct are described below. The ends of the channel may include suitable fittings (not shown) for connection to other system components when in place.

The panel 10 is encapsulated and sealed around its periphery by a layer 22 of non-porous, heat and flameresistant material, typically a bagging material such as lightweight, fibre-reinforced PVF film applied to the external surfaces of the panel by tailoring and adhesive bonding or heat sealing.

The channel 12 is lined/sealed using a layer 22 of nonmetallic material. For example, it may be lined using the same material as used to encapsulate the panel 10.

Alternatively the lining may be glass, aramid or ceramic fibre reinforced, resin impregnated, laminated material. This may be constructed from either preimpregnated tape or fabric material, or from wet lay-up resin impregnated fabric materials. The resin may be modified phenolic resin or similar. As a further alterative, the lining may be a polymeric material applied as a film or by brush or spray methods.

The density of the foam material may vary according to specific requirements, and may be varied locally within a single aircraft in order to provide enhanced insulation in particular locations. Individual panels may also be composites of layers of materials having differing characteristics, including density. The relative thickness of the layers may also vary. One or more additional laminations of high density material may also be incorporated into the panel, suitably between the outer and inner layers, to provide additional sound-proofing. Such an additional lamination is indicated by reference numeral 24 in Fig.

2. In general, however, the density or densities of the material(s) will be kept as low as possible, consistent with the required level of sound insulation.

The insulating panels provided by the invention may be constructed to predetermined shapes. Adjacent panels may be butt joined or may be fabricated with stepped, overlapping joints, and may be configured to fit around stringers, frames etc.

Preferred materials and fabrication methods are described, but alternative materials and methods may be substituted which meet such requirements for flame, smoke, toxicity and burn-through performance as may be applicable. The assembly as a whole will generally be required to maintain its shape, thickness and exterior dimensions. It will also be required to be robust, tear and puncture resistant, resilient, and generally resistant to degradation in normal conditions of handling and use.

The invention thus provides an acoustically and thermally insulating panel which can be fabricated to relatively precise dimensions and specifications, with integrally formed duct channels obviating the need for separate assemblies of conduits.

Improvements and modifications may be incorporated without departing from the scope of the invention.

Claims

1. An insulating element comprising a panel of predetermined shape formed from an acoustically and thermally insulating foamed polymeric material which is at least semi-rigid, the panel having at least one channel defining a duct extending at least partially therethrough.

2. An insulating element as claimed in Claim 1, wherein the exterior surfaces of said panel are covered and sealed around its periphery by a layer of non-porous material.

3. An insulating element as claimed in Claim 1 or Claim 2, wherein the foamed polymeric material is an opencelled polyimide foam.

4. An insulating element as claimed in any preceding Claim, wherein said at least one channel is lined by a layer of non-porous, non-metallic material so as to be sealed from the foam material of the panel.

5. An insulating element as claimed in Claim 2 or Claim 4, wherein the non-porous material covering the panel and/or lining the channel is heat and flame resistant.

6. An insulating element as claimed in Claim 6, wherein the non-porous material covering the panel and/or lining the channel is a lightweight, fibre reinforced PVF film.

7. An insulating element as claimed in Claim 4, or Claim 5, wherein the non-porous material lining the channel is glass, aramid or ceramic fibre reinforced, resin impregnated, laminated material.

8. An insulating element as claimed in Claim 7, wherein said material is a modified phenolic resin or similar.

9. An insulating element as claimed in Claim 4 or Claim 5, wherein the lining is formed from a polymeric material applied as film, or by brush or spray methods.

10. An insulating element as claimed in any preceding Claim, wherein the panel comprises first and second outer layers of foamed polymeric material and at least one inner layer sandwiched between said outer layers, said at least one channel being formed by cutting said inner layer.

11. An insulating element as claimed in Claim 10, further including at least one additional layer of material of higher density than said outer layers.

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