Polyimide aerogel insulated panel assembly

A panel assembly that includes a core having first and second opposing major surfaces, a first laminate skin secured to the first major surface of the core, a second laminate skin secured to the second major surface of the core, and at least a first layer of polyimide aerogel incorporated into one of the first laminate skin or the second laminate skin.

FIELD OF THE INVENTION

The present invention relates generally to a panel assembly, and more particularly to a panel assembly insulated by polyimide aerogel.

BACKGROUND OF THE INVENTION

Thermal insulation is important on aircraft, particularly, for example, for active chilling/heating systems for food and drinks on an aircraft. The more thermally efficient or thermally insulated panel assemblies (e.g., honeycomb core panels) on an aircraft are, the better. Accordingly, a need exists for a method to insulate a honeycomb core panel assembly and/or a laminate assembly associated with the panel with a material, such as polyimide aerogel, that is of light weight, low thermal conductivity and high compressive strength for the purposes of insulating and withstanding the honeycomb core panel and laminate production processes.

SUMMARY OF THE PREFERRED EMBODIMENTS

In accordance with a first aspect of the present invention there is provided a panel assembly that includes a core having first and second opposing major surfaces, a first laminate skin secured to the first major surface of the core, a second laminate skin secured to the second major surface of the core, and at least a first layer of polyimide aerogel incorporated into one of the first laminate skin or the second laminate skin. In a preferred embodiment, the first laminate skin includes a first ply and the first layer of polyimide aerogel. Preferably, the second laminate skin includes a first ply and a second layer of polyimide aerogel. In a preferred embodiment, the first laminate skin includes first and second plies having the first layer of polyimide aerogel sandwiched therebetween and the second laminate skin includes first and second plies having the second layer of polyimide aerogel sandwiched therebetween. Preferably, the core is a honeycomb core. In a preferred embodiment, the honeycomb core includes polyimide aerogel incorporated therein. The polyimide aerogel is incorporated into one or more cells of the honeycomb core by the steps of applying a polyimide aerogel producing mixture to one or more cells of the honeycomb core; and supercritically drying the mixture to produce a layer of polyimide aerogel on the one or more cells of the honeycomb core.

In accordance with another aspect of the present invention there is provided a method of producing an insulated panel assembly that includes obtaining or providing a core having first and second opposing major surfaces, obtaining or providing a first ply of material, obtaining or providing a first layer of polyimide aerogel, adhering the first layer of polyimide aerogel to the first ply of material to provide a first laminate skin, obtaining or providing a second ply of material, obtaining or providing a second layer of polyimide aerogel, adhering the second layer of polyimide aerogel to the second ply of material to provide a second laminate skin, positioning the first and second laminate skins adjacent to the first and second major surfaces of the core, respectively, to provide a panel assembly, pressing the panel assembly, and heating the panel assembly to provide the insulated panel assembly. In a preferred embodiment, the first laminate skin includes first and second plies that sandwich the first layer of polyimide aerogel therebetween and the second laminate skin includes first and second plies that sandwich the second layer of polyimide aerogel therebetween. Preferably, the method also includes the step of pouring a sol-gel mixture into the honeycomb core prior to heating.

In accordance with another aspect of the present invention there is provided a laminate assembly that includes a first ply comprised of a first material, a first layer of polyimide aerogel adhered to the first ply. In a preferred embodiment, the first material is impregnated with a resin and is either carbon or fiberglass. Preferably, one of the first ply or the first layer of polyimide aerogel includes an adhesive thereon, such that the laminate assembly can be secured to a surface. The present invention also includes an aircraft that has an interior surface having the laminate assembly adhered thereto.

In accordance with another aspect of the present invention there is provided a method for insulating a honeycomb core panel assembly. The method includes providing a layer of aerogel, and incorporating the layer of aerogel into the honeycomb core panel assembly. In a preferred embodiment, the providing a layer of aerogel includes the steps of providing a mixture of a solvent and a polymer, supercritically drying the mixture to remove liquid from the mixture and to generate a mass of aerogel, and preparing the mass of aerogel into a layer of aerogel of a size. Preferably, the incorporating the layer of aerogel includes the steps of positioning the layer of aerogel between a first element of the honeycomb core panel assembly and a second element of the honeycomb core panel assembly, and bonding the layer of aerogel to the first and/or the second elements of the honeycomb core panel assembly. Preferably, the first element and the second element of the honeycomb core panel assembly are plies of a skin of the honeycomb core panel assembly or the first element is a skin of the honeycomb core panel assembly and the second element is a honeycomb core of the honeycomb core panel assembly. In a preferred embodiment, the bonding the layer of aerogel to the first and second elements of the honeycomb core assembly is done by resin bonding or adhesive agent based. The adhesive agent is preferably selected from the group consisting of urethane and mixtures thereof. In a preferred embodiment, the skin of the honeycomb core panel assembly is a laminate skin and the aerogel is polyimide aerogel.

In accordance with another aspect of the present invention there is provided a method for insulating a honeycomb core panel assembly that includes applying an aerogel producing mixture to one or more cells of the honeycomb core, supercritically drying the mixture to generate a layer of aerogel on the honeycomb core, and configuring the honeycomb core into the honeycomb core panel assembly. Preferably, the mixture comprises a solvent and a polymer and produces polyimide aerogel upon critical drying.

In accordance with another aspect of the present invention there is provided a method for modifying a honeycomb core that includes applying an aerogel producing mixture to one or more cells of the honeycomb core, and supercritically drying the mixture to generate a layer of aerogel on the honeycomb core. Preferably, the applying an aerogel producing mixture comprises applying the mixture to one or more cell-defining panels of substrate, wherein the cell-defining panels of substrate are configured into the honeycomb core.

In accordance with another aspect of the present invention there is provided an insulated honeycomb core panel assembly that includes a honeycomb core having top and bottom surfaces, a pair of skins, and one or more layers of aerogel. Each of the pair of skins is attached to one of the top and bottom surfaces of the honeycomb core, and one or more layers of aerogel are incorporated in the honeycomb core panel assembly. Preferably, the one or more layers of aerogel is positioned between and bonded to the honeycomb core and one of the pair of skins. Or the one or more layers of aerogel is positioned between and bonded to the honeycomb core and both of the pair of skins.

In accordance with another aspect of the present invention there is provided a method for insulating a laminate panel assembly. The method includes providing a layer of aerogel and incorporating the layer of aerogel into the laminate assembly. In a preferred embodiment, the incorporating the layer of aerogel comprises the steps of positioning the layer of aerogel between a first ply of the laminate assembly and a second ply of the laminate assembly, and bonding the layer of aerogel to the first ply or the first and second plies of the laminate assembly.

Aerogels are generally highly porous materials exhibiting very low density and very low thermal conductivity. Incorporating a polyimide aerogel into a honeycomb core panel or laminate assembly can provide thermal insulation for aircraft and aircraft part assemblies, and may reduce or even eliminate the need to for active chilling/heating systems food and drinks on an aircraft.

It will be appreciated by those of ordinary skill in the art that polyimide aerogels can be formed by first combining a polymer with a solvent to form a so-gel mixture, and then removing the liquid from the so-gel mixture, through processes such as supercritical drying techniques. Supercritical drying can be done in a solvent extracting autoclave to produce a mass of aerogel. Polyimide aerogels can be molded or machined into a ply of a desired shape, size or thickness. In another embodiment, the aforementioned sol-gel mixtures can be applied to a component or structure to be insulated, and then supercritically dried into forming polyimide gel layers in situ of the component or the structure.

After pouring the sol-gel mixture into the core, the core is placed in an autoclave system where pressure is manipulated so that there is no surface tension and then either chemicals or a vacuum is used to bleed out most to all of the moisture. The aerogel is then formed and then the core is infused with or filled with aerogel.

Polyimide aerogels are taught in U.S. Publication No. 2004/0132845 published on Jul. 8, 2004, the entirety of which is incorporated herein by reference. Polyimide aerogels are also taught in the following publications, the entireties of which are incorporated by reference herein:

The invention, together with additional features and advantages thereof, may be best understood by reference to the following description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference in this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Appearances of the phrase “in one embodiment” in various places in the specification do not necessarily refer to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but not other embodiments.

The terms used in this specification generally have their ordinary meanings in the art, within the context of the disclosure, and in the specific context where each term is used. Certain terms that are used to describe the disclosure are discussed below, or elsewhere in the specification, to provide additional guidance to the practitioner regarding the description of the disclosure.

It will be appreciated that terms such as “front,” “back,” “top,” “bottom,” “side,” “short,” “long,” “up,” “down,” and “below” used herein are merely for ease of description and refer to the orientation of the components as shown in the figures. It should be understood that any orientation of the components described herein is within the scope of the present invention.

Referring now to the drawings, wherein the showings are for purposes of illustrating the present invention and not for purposes of limiting the same,FIGS. 1-4show a variety of exemplary embodiments of the present invention.

Described herein are preferred embodiments of a polyimide aerogel insulated panel assembly and a method for making same. The method includes insulating a honeycomb core panel assembly and a laminate assembly with polyimide gels. Generally, the method includes providing a layer of polyimide gel, and incorporating the layer of polyimide gel into the honeycomb core panel assembly, or a laminate assembly. In another embodiment, the method includes providing a polyimide aerogel-producing sol-gel mixture to a honeycomb core structure and supercritically drying the core to form a polyimide gel coated or infused honeycomb core, which can incorporated into a honeycomb core panel assembly.

Referring now toFIG. 1, a preferred embodiment of a honeycomb core panel assembly100is shown. It will be appreciated that the core can be material other than a honeycomb material. For example, the core can be a foam material. For exemplary purposes only, the drawings and description herein include a honeycomb core. However, this is not a limitation on the present invention. The honeycomb core108can be any known material. For example, the core can be paper, Kevlar, Nomex or the like. The honeycomb core panel assembly100generally includes a first laminate skin101, a honeycomb core108and a second laminate skin103. Generally, the laminate skins can include any number of plies together with one or more layers of polyimide aerogel. For example, as shown inFIG. 1, in a preferred embodiment, the first laminate skin101includes a layer of polyimide aerogel106positioned between a first ply102and a second ply104, and the second laminate skin103includes a layer of polyimide aerogel112positioned between a first ply110and a second ply114. Those of the ordinary skill in the art will understand that layers of polyimide aerogel106and112can be provided in various thicknesses to affect various degrees of thermal insulation.

The plies102,104,110and114can be made of carbon, fiberglass or other desired material. For example, ply102can be a fiberglass or carbon weave that is impregnated with resin prior to being adhered to either the core108or the polyimide aerogel layer106. Layers of polyimide aerogel106and112may be resin bonded to the plies. Adhesives agents such as acrylic based or urethane based adhesives (e.g., 3M 3532) for bonding the various layers together. Generally, to make the panel assembly100, the layers of skin (plies and polyimide aerogel layer) are sandwiched about the core, adhesive films are provided where desired to adhere the layers together and then the entire assembly is pressed within a hot press and baked and cured to provide a rigid panel assembly100. Any number of layers of ply and/or any number of layers of polyimide aerogel insulation is within the scope of the present invention. For example, if the panel assembly is to be used in an area that takes a heavy beating, multiple layers of carbon ply can be used to provide impact resistance.

FIG. 2shows another preferred embodiment of a honeycomb core panel assembly200with laminate skins201and203with only a single ply202and214together with a layer of polyimide aerogel204and212. As shown, the honeycomb core panel assembly200preferably includes a first ply or layer202, a honeycomb core208, and a second ply or layer214. A layer of polyimide aerogel204is introduced and positioned between the first ply202and the honeycomb core208. Another layer of polyimide aerogel212is additionally or independently introduced and positioned between the second ply or layer214and the honeycomb core208. It should be appreciated that the laminate skins can be one or more plies of fiberglass or carbon laminate (or other material) and the construction may not be symmetrical. For example, in a panel assembly there may be situations where there are more plies (or layers of polyimide aerogel) on one side than another for specific side impact resistance purposes. In another embodiment, the polyimide aerogel insulation may be only used on one side of the panel assembly.

Panel assemblies, such as those described above and shown inFIGS. 1-2can be used throughout an aircraft, such as in any type of common aircraft monument (e.g., lavatories, galleys, closets, bulkheads, storage areas) or in the walls, ceiling, floor, doors, overhead storage bins and other areas in an aircraft.

FIG. 3shows a polyimide aerogel insulated laminate assembly300. Generally, the laminate assembly300includes at least a first ply or layer302together with at least one layer of polyimide aerogel306. The embodiment shown inFIG. 3includes the first ply of laminate material302and a second ply of laminate material304and the layer of polyimide aerogel306is introduced and positioned between the first ply302and the second ply304. The layer of polyimide aerogel306may be bonded to the first ply302using an adhesive layer308on one side, and bonded to the second ply304using an adhesive layer310on the other side. Adhesives may be selected from adhesive agents such as acrylic based or urethane based adhesives (e.g., 3M 3532) for a good quality wet-out and bonding. Other types of adhesives are within the scope of the present invention as well. It will be appreciated that adhesive layer308and310may form a continuous layer or be applied in a non-continuous manner (as shown inFIG. 3) as long as the effect of the bonding of the polyimide aerogel layer306to the first and the second plies302and304can be achieved. Any number of plies and polyimide aerogel layers is within the scope of the present invention. For example, the insulated laminate assembly may include multiple layers of polyimide aerogel sandwiched between a pair of plies. Furthermore, as shown inFIG. 3, an adhesive layer312can be included on the outside surface of one or both of the first and the second plies302and304so that the laminate assembly300can be adhered to a surface.

It will be appreciated by those of ordinary skill in the art that the polyimide aerogel insulated laminate assembly300can be applied to components within an aircraft or the like. For example, as shown inFIG. 4, one or more laminate assemblies300can be adhered to the inside or outside surface of a meal cart320.FIG. 4shows a first laminate assembly300adhered to one side of the cart320and a second laminate assembly320exploded form the other side of the meal cart320. By doing this, the insulative properties of an existing meal cart can be improved. Laminate assemblies300can also be used in other areas of an aircraft, such as in any type of common aircraft monument (e.g., lavatories, galleys, closets, bulkheads, storage areas) or on the walls, ceiling, floor, doors, overhead storage bins and other areas in an aircraft where insulation is desired. For example, galleys often include a refrigerated compartment in which it is undesirable for the panels therein to sweat. Also, refrigerated compartments and ovens are often in close proximity. By placing laminate assemblies300on the appropriate surfaces, the insulation properties can be improved.

FIG. 5shows a honeycomb core500with a polyimide aerogel incorporated or infused therein. The honeycomb core500is comprised of a plurality of layers of cell-defining panels, each having an upper surface502and bottom surface504. To create the honeycomb core500, a polyimide aerogel producing sol-gel mixture is applied to the entire honeycomb core500(e.g., by pouring it into the core), certain selective layers of the cell-defining panels of the honeycomb core500or certain selective cells of the honeycomb core500. In one preferred embodiment, the entire honeycomb core500may be infused with the so-gel mixture, which is subsequently supercritically dried on the honeycomb core500to form a honeycomb core entirely infused or covered with polyimide aerogel. In another preferred embodiment, the sol-gel mixture may be applied selectively to certain the upper and/or bottom surfaces of certain layers of panels of the honeycomb core500. In this embodiment, after supercritical drying the honeycomb core500is partially infused with polyimide aerogel. In an embodiment, polyimide aerogel can be included in both the core (as shown inFIG. 5) and in the laminate skin(s) (as shown inFIGS. 1-2).