US20100050553A1

US20100050553A1 - sandwich panel joint and method of joining sandwich panels

Info

Publication number: US20100050553A1
Application number: US12/201,687
Authority: US
Inventors: Robert Alan Schofield
Original assignee: Innovida Factories Ltd
Current assignee: MILLPORT ASSOCIATES SA
Priority date: 2008-08-29
Filing date: 2008-08-29
Publication date: 2010-03-04

Abstract

Structural connections between foam cored composite panels are formed using structural bonding tape. The structural bonding tape includes a structural adhesive layer and a reinforcement fabric of fibers at least partially embedded within the layer of adhesive. The structural adhesive is cured upon exposure to ultraviolet radiation.

Description

TECHNICAL FIELD

The present invention relates generally to constructing buildings, and more particularly, to making structural connections between foam cored composite panels using a structural bonding tape.

BACKGROUND

There is an increasing global demand for lower cost buildings such as houses, warehouses and office space. The demand for lower cost buildings is particularly strong in developing countries where economic resources may be limited and natural resources and raw materials may be scarce. For example, in areas of the Middle East or Africa, conventional building materials such as cement, brick, wood or steel may not be readily available or, if available, may be very expensive. In other areas of the world, poverty may make it too costly for people to build houses or other buildings with conventional materials.
The demand for lower cost housing also is high in areas afflicted by war or natural disasters, such as hurricanes, tornados, floods, and the like. These devastating events often lead to widespread destruction of large numbers of buildings and houses, especially when they occur in densely populated regions. The rebuilding of areas affected by these events can cause substantial strain on the supply chain for raw materials, making them difficult or even impossible to obtain. Furthermore, natural disasters often recur and affect the same areas. If a destroyed building is rebuilt using the same conventional materials, it stands to reason that the building may be destroyed or damaged again during a similar event.
It is generally desirable to increase speed of construction and to minimize construction costs. Prefabricated or preassembled components can streamline production and reduce both the time and the cost of building construction. Prefabricated buildings, however, are made from conventional materials that may be scarce or expensive to obtain. Thus, there exists a need for alternative materials and techniques for constructing buildings that use advanced material technologies to increase the speed of construction and to reduce or to lower ownership costs.

SUMMARY

The present invention provides an alternative to conventional construction materials and techniques. Buildings, such as houses, commercial buildings, warehouses, or other structures can be constructed by composite sandwich panels (also referred to as “sandwich panels” or “composite panels”), which have an insulative core and one or more outer layers. The buildings can be constructed by gluing several sandwich panels together. Traditional fasteners, such as screws, rivets, nails, etc., are usually not needed for such connections. Generally, composite sandwich panels offer a greater strength-to-weight ratio than traditional materials that are used by the building industry. The composite sandwich panels are generally as strong as, or stronger than, traditional materials including wood-based and steel-based structural insulation panels, while being lighter in weight. Because they weigh less than traditional building materials, the handling and transport of composite sandwich panels is generally less expensive. The composite sandwich panels also can be used to produce light-weight structures, such as floating houses, mobile homes, or travel trailers, etc.
Sandwich panels generally are more elastic or flexible than conventional materials such as wood, concrete, steel or brick and, therefore, monolithic (e.g., unitary or single unit structure) buildings made from sandwich panels generally are more durable than buildings made from conventional materials. For example, sandwich panels also may be non-flammable, waterproof, very strong and durable, and in some cases, able to resist hurricane-force winds (up to 300 Kph (kilometers per hour) or more). The sandwich panels also may be resistant to the detrimental effects of algae, fungicides, water, and osmosis. As a result, buildings constructed from sandwich panels may be better able to withstand earthquakes, floods, tornados, hurricanes, fires and other natural disasters than buildings constructed from conventional materials.
Sandwich panel structures may be less expensive to build than structures built from conventional materials because of reduced material costs and alternative construction techniques. The ownership and maintenance costs for sandwich panel structures also may be less over the long term because sandwich panel structures may last longer and degrade at a slower rate than buildings made from conventional materials. Structures built from sandwich panels therefore may require less maintenance and upkeep than structures built from conventional building materials, which may reduce the overall ownership costs for end users.
The insulative core of the sandwich panels also may reduce the amount of energy needed to heat and/or cool the building, which may reduce the overall costs to operate the building. The insulative core also may reduce or eliminate the need for additional insulation in the building, as may be necessary to insulate structures built from conventional building materials. Sandwich panel structures therefore may be less expensive to build and operate than buildings constructed from conventional building materials.
A number of construction elements, e.g., one or more composite sandwich panels can be connected together, for example, to erect walls, to build ceilings or roofs, or to divide the interior of the building into one or more rooms, etc. As described in more detail below, a number of sandwich panels can be connected together to form a multi-panel wall segment. A number of multi-panel wall segments can be connected together in a parallel orientation with bonding material to form a double wall segment (e.g., a wall segment that is two panels thick). The double wall segment may be used, for example, to support an upper portion or second level of a building or to strengthen the walls of the building, etc.
With the method and tape of the present invention, the composite panels may be joined together to form an integrated structure using a bonding tape constructed of an adhesive resin impregnated fiber reinforcement. The bonding tape is precut and may be provided in the form of a roll or packaged lengths of tape. The adhesive resin does not cure unless exposed to sunlight or an ultraviolet light source. The tape is provided with a removable opaque release overlay film that protects the adhesive. At the jobsite, the tape is applied to the panel joint and the opaque overlay film is removed, allowing light to cause the resin to cure and the two adjacent sandwich panels to become permanently bonded together in a structural connection. Corner joints, panel seams, butt joints and roof seams can be adhesively bonded together with the bonding tape to form a watertight, weatherproof, solid structural connection that will last for the life of the building.
In one aspect of the invention there is provided a joint connecting a first sandwich panel and a second sandwich panel, the joint including: a first sandwich panel having a first outer layer and a second outer layer spaced from the first outer layer by a panel core, and an edge including an edge portion of the panel core, an edge portion of the first outer layer and an edge portion of the second outer layer; a second sandwich panel having a first outer layer and a second outer layer spaced from the first outer layer by a panel core, and an edge including an edge portion of the panel core, an edge portion of the first outer layer and an edge portion of the second outer layer, wherein the edges of the sandwich panels are in contact with one another at an interface between the panels; and a structural bond formed at the interface on the first outer surfaces of the panels, the structural bond including a layer of structural adhesive material and at least one reinforcement fabric of fibers at least partially embedded within the layer of adhesive material, wherein the structural adhesive layer is cured upon exposure to ultraviolet radiation.
According to an embodiment of the invention, the layer of adhesive material includes at least one UV curable resin chosen from (meth)acrylates, epoxy, polyurethanes, vinyl esters, polyester, phenolic, silicone resins, and mixtures of two or more thereof. In one embodiment of the invention, the layer of adhesive material included at least one UV curable (meth)acrylate resin.
According to one aspect of the invention, the reinforcement fabric is chosen from fiberglass mesh, woven fabrics, non-woven fabrics, knitted fabrics and a unidirectional array of fibers. In one embodiment, the reinforcement fabric includes a fiberglass mesh.
In one embodiment, the fibers of the reinforcement fabric are chosen from polyester, polyolefin, aramid, cotton, sisal, jute, hemp, glass, carbon, ceramic, and coated fibers having a basic component and a coating thereon.
According to one aspect of the invention, the joint further includes a second structural bond formed at the interface on the second outer surfaces of the panels, the structural bond comprising a layer of structural adhesive material and at least one reinforcement fabric of fibers at least partially embedded within the layer of adhesive material, wherein the structural adhesive layer is cured upon exposure to ultraviolet radiation.
According to another aspect of the invention, there is provided a method of joining sandwich panels including: providing a first sandwich panel having a first outer layer and a second outer layer spaced from the first outer layer by a panel core, and an edge comprised of an edge portion of the panel core, an edge portion of the first outer layer and an edge portion of the second outer layer; providing a second sandwich panel having a first outer layer and a second outer layer spaced from the first outer layer by a panel core, and an edge comprised of an edge portion of the panel core, an edge portion of the first outer layer and an edge portion of the second outer layer; contacting the edges of the sandwich panels with one another at an interface between the panels; applying a bonding tape to the interface on the first outer surfaces of the panels, the bonding tape having an inner surface and an outer surface and comprising a layer of ultraviolet curable structural adhesive material and at least one reinforcement fabric at least partially embedded within the layer of adhesive material; and exposing the adhesive material to a source of ultraviolet radiation to form a structural bond between the first panel and the second panel at the interface.
In one embodiment, the source of ultraviolet radiation is sunlight.
In another embodiment, the bonding tape further includes an opaque overlay film on the outer surface. The opaque overlay film is removed prior to exposure to ultraviolet radiation.
In one aspect of the invention, there is provided an architectural edifice including a joint connecting a first sandwich panel and a second sandwich panel, the joint including: a first sandwich panel having a first outer layer and a second outer layer spaced from the first outer layer by a panel core, and an edge including an edge portion of the panel core, an edge portion of the first outer layer and an edge portion of the second outer layer; a second sandwich panel having a first outer layer and a second outer layer spaced from the first outer layer by a panel core, and an edge including an edge portion of the panel core, an edge portion of the first outer layer and an edge portion of the second outer layer, wherein the edges of the sandwich panels are in contact with one another at an interface between the panels; and a structural bond formed at the interface on the first outer surfaces of the panels, the structural bond including a layer of structural adhesive material and at least one reinforcement fabric at least partially embedded within the layer of adhesive material, wherein the structural adhesive layer is cured upon exposure to ultraviolet radiation..
In another aspect of the invention, there is provided an architectural edifice made according to the method of joining sandwich panels including: providing a first sandwich panel having a first outer layer and a second outer layer spaced from the first outer layer by a panel core, and an edge comprised of an edge portion of the panel core, an edge portion of the first outer layer and an edge portion of the second outer layer; providing a second sandwich panel having a first outer layer and a second outer layer spaced from the first outer layer by a panel core, and an edge comprised of an edge portion of the panel core, an edge portion of the first outer layer and an edge portion of the second outer layer; contacting the edges of the sandwich panels with one another at an interface between the panels; applying a bonding tape to the interface on the first outer surfaces of the panels, the bonding tape having an inner surface and an outer surface and comprising a layer of ultraviolet curable structural adhesive material and at least one reinforcement fabric at least partially embedded within the layer of adhesive material; and exposing the adhesive material to a source of ultraviolet radiation to form a structural bond between the first panel and the second panel at the interface.
These and further features of the present invention will be apparent with reference to the following description and attached drawings. In the description and drawings, particular embodiments of the invention have been disclosed in detail as being indicative of some of the ways in which the principles of the invention may be employed, but it is understood that the invention is not limited correspondingly in scope. Rather, the invention includes all changes, modifications and equivalents coming within the spirit and terms of the claims appended hereto.
It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.
Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with, or instead of, the features of the other embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary environmental view of an exemplary monolithic structure built with composite materials.

FIG. 2 is an isometric view of an exemplary sandwich panel.

FIG. 3 is a cross-sectional view of an exemplary bonding tape.

FIG. 4 is a cross-sectional view of an exemplary bonding tape in a roll configuration.

FIGS. 5A and 5B are cross-sectional views of an exemplary bonding tape as applied to a panel joint prior to cure.

FIG. 6 is an isometric view of a first panel bonded to a second panel via the bonding tape.

FIG. 7 is an isometric view of a corner joint of a first panel and a second panel and the bonding tape joining the two panels.

DETAILED DESCRIPTION

In the detailed description that follows, like components have been given the same reference numerals regardless of whether they are shown in different embodiments of the invention. To illustrate the present invention in a clear and concise manner, the drawings may not necessarily be to scale and certain features may be shown in somewhat schematic form. Certain terminology is used herein to describe the different embodiments of the invention. Such terminology is used for convenience when referring to the figures. For example, “upward,” “downward,” “above,” “below,” “left,” or “right” merely describe directions in the configurations shown in the figures. Similarly, the terms “interior” and exterior” or “inner” and “outer” may be used for convenience to describe the orientation of the components in the figures. The components can be oriented in any direction and the terminology should therefore be interpreted to include such variations. The dimensions provided herein are exemplary in nature and are not intended to be limiting in scope. Furthermore, while described primarily with respect to house construction, it will be appreciated that the concepts described herein are equally applicable to the construction of any type of structure or building, such as warehouses, commercial buildings, factories, apartments, etc.
The structures described herein are built with composite materials, such as composite sandwich panels. The sandwich panels may be formed from synthetic or natural materials and may provide a light-weight and potentially less expensive alternative to conventional raw materials, e.g., wood, concrete, metal, etc. The sandwich panels may be connected or joined together with a high-strength bonding material, such as epoxy or glue. The result is a strong and durable monolithic structure, as is described further below.
Referring to FIG. 1, an exemplary monolithic structure 10, for example, a house, is built from a number of sandwich panels that are connected together with bonding material. A front wall 10 f of the house 10 is formed from sandwich panels 11-16. A side wall 10 s of the house 10 is formed from sandwich panels 20-23. The sandwich panels are connected together to form a number of multi-panel wall segments, which are connected together to form the walls 10 f, 10 s.
The house 10 includes a top portion 10 t and a bottom portion 10 b. The top portion 10 t of the front wall 10 f of the house includes a multi-panel wall segment formed by connecting sandwich panel 13 and sandwich panel 14 together. The top portion 10 t of the side wall 10 s includes a multi-panel wall segment formed by connecting sandwich panel 22 and sandwich panel 23 together.
The top portion 10 t of the house 10 is supported by the bottom portion 10 b of the house 10. The bottom portion 10 b may be a double wide wall segment that is used to support the top portion 10 t. The bottom portion 10 b of the side wall 10 s may include a number of multi-panel wall segments connected together by a joint 24 a. As shown in the cut-away portion 25 of FIG. 1, the double wide wall segment can be used to support a floor 26 and/or other top portion 10 t of the house 10. The double wide wall segment includes an outer multi-panel wall segment 30 connected to an inner multi-panel wall segment 31.
An exemplary sandwich panel 50 is shown in FIG. 2. The sandwich panel 50 includes two outer layers 51, 52 separated by a core 53. The outer layers 51, 52 are bonded or adhered to the core 53 with bonding material.
The core 53 of the exemplary sandwich panel 50 may be formed from a light-weight, insulative material, for example, polyurethane, expanded polystyrene, polystyrene hard foam, Styrofoam material, phenolic foam, a natural foam, for example, foams made from cellulose materials, such as a cellulosic corn-based foam, or a combination of several different materials. Other exemplary core materials include honeycomb that can be made of polypropylene, non-flammable impregnated paper or other composite materials. It will be appreciated that these materials thermally insulate the interior of the structure and also reduce the sound or noise transmitted through the panels. The core may be any desired thickness and may be, for example, about 30 mm (millimeters)-100 mm (millimeters) thick, however, it will be appreciated that the core can be thinner than 30 mm (millimeters) or thicker than 100 mm (millimeters) as may be desired. In one embodiment, the core is about 60 mm (millimeters) thick.
The outer layers 51, 52 of the sandwich panel 50, are made from a composite material that includes a matrix material and a filler or reinforcement material. Exemplary matrix materials include a resin or mixture of resins, e.g., epoxy resin, polyester resin, vinyl ester resin, natural (or non oil-based) resin or phenolic resin, etc. Exemplary filler or reinforcement materials include fiberglass, glass fabric, carbon fiber, or aramid fiber, etc. Other filler or reinforcement materials include, for example, one or more natural fibers, such as, sisal, jute, coco, hemp, or elephant grass, balsa wood, or bamboo.
The outer layers 51, 52 (also referred to as laminate) may be relatively thin with respect to the panel core 53. The outer layers 51, 52 may be several millimeters thick and may, be, for example between about 1 mm (millimeter)-12 mm (millimeters) thick, however, it will be appreciated that the outer layers can be thinner than 1 mm or thicker than 12 mm as may be desired. In one embodiment, the outer layers are about 1-3 mm thick.
It will be appreciated that the outer layers 51, 52 may be made thicker by layering several layers of reinforcement material on top of one another. The thickness of the reinforcement material also may be varied to obtain thicker outer layers 51, 52 with a single layer of reinforcement material. Further, different reinforcement materials may be thicker than others and may be selected based upon the desired thickness of the outer layers.
The outer layers 51, 52 are adhered to the core 53 with the matrix materials, such as a resin mixture. Once cured, the outer layers 51, 52 of the sandwich panel 50 are firmly adhered to both sides of the panel core 53, forming a rigid building element. It will be appreciated that the resin mixture also may include additional agents, such as, for example, flame retardants, mold releases, curing agents, hardeners, etc. Coatings may be applied to the outer layers 51, 52, such as, for example, finish coats, paint, ultra-violet (UV) protectants, water protectants, etc.
The core 53 may provide good thermal insulation properties and structural properties. The outer layers 51, 52 may add to those properties of the core and also may protect the core 53 from damage. The outer layers 51, 52 also provide rigidity and support to the sandwich panel.
The sandwich panels may be any shape. In one embodiment, the sandwich panels are rectangular in shape and may be several meters, or more, in height and width. The sandwich panels also may be other shapes and sizes. The combination of the core 53 and outer layers 51, 52 create sandwich panels with high ultimate flexural, tensile, shear, and compressive strength, which is the maximum stress the panels can withstand before failure. The compressive strength of the panels is such that the panels may be used as both load bearing and non-load bearing walls. In one embodiment, the panels have a load capacity of at least 50 tons per square meter in the vertical direction (indicated by arrows V in FIG. 2) and 2 tons per square meter in the horizontal direction (indicated by arrows H in FIG. 2). The sandwich panels may have other strength characteristics as will be appreciated in the art.
Internal stiffeners may be integrated into the panel core 53 to increase the overall stiffness of the sandwich panel 50. In one embodiment, the stiffeners are made from materials having the same thermal expansion properties as the materials used to construct the panel, such that the stiffeners expand and contract with the rest of the panel when the panel is heated or cooled.
The stiffeners may be made from the same material used to construct the outer layers of the panel. The stiffeners may be made from composite materials and may be placed perpendicular to the top and bottom of the panels and spaced, for example, at distances of 15 cm (centimeters), 25 cm, 50 cm, or 100 cm. Alternatively, the stiffeners may be placed at different angles, such as a 45-degree angle with respect to the top and bottom of the panel, or at another angle, as may be desired.
The structural bonding tape used to join the two adjacent composite panels includes a fiber reinforcement fabric and an adhesive resin composition impregnated in the fiber reinforcement fabric. The adhesive resin is cured by exposing the tape to a light source on one side of the tape. The light source may be an ultraviolet lamp or may be sunlight.
In FIG. 3, an exemplary bonding tape useful for joining composite panels is shown. The exemplary bonding tape 60 includes an adhesive layer 61 containing a fiber reinforcement fabric 62, and an opaque overlay film 63 on an outer surface 64 of the adhesive layer 61.
The fiber reinforcement fabric is sufficiently porous and light permeable to enable the adhesive to be fully cured by UV radiation. In addition, the fiber reinforcement fabric possesses an overall thickness and weight to provide strength to the structural bonding tape. The fiber reinforcement fabric may include a fiber-containing fabric such as fiberglass mesh, woven fabrics, non-woven fabrics, knitted fabrics and a unidirectional array of fibers. The fibers used to form the reinforcement fabric may be chosen from the following non-limiting examples: polymeric materials such as polyesters, polyolefins and aramids; organic materials such cotton, sisal, jute and hemp; inorganic materials such as glass, carbon and ceramic; and coated fibers having a core component and a coating thereon.
The adhesive resin used in the fiber reinforced tape may be a structural adhesive. This group of adhesives generally encompasses those materials with high cohesive strength used to bond adherends also with significant cohesive strength, such as wood, composites or metal. The typical bond strengths of structural adhesives may be in excess of 6.9 MPa (1000 psi) at room temperature. Structural adhesives are usually crosslinkable organic compounds, are usually polar and of high surface energy. In addition, structural adhesives are typically resistant to many types of environmental attack. Suitable structural adhesives include low flow adhesives that are UV (ultraviolet) curable. Examples of useful UV curable adhesive resins include (meth)acrylates, epoxy, polyurethanes, vinylesters, polyester, phenolic and silicone resins. The adhesive layer of the tape has sufficient cohesive integrity to provide ease of complete transfer to the adherend and the substantial inhibition of loss of the adhesive while in tapes or sheets through edge ooze.
(Meth)acrylate: The adhesive resin composition, in one embodiment, includes one or more thermoplastic (meth)acrylate resins. Monomers useful for making the (meth)acrylate resins include, but are not limited to: acrylic acid esters of an alkyl alcohol (desirably a non-tertiary alcohol), wherein the alcohol contains from 1 to about 14 (desirably from about 4 to about 14) carbon atoms and include, for example, methyl acrylate, ethyl acrylate, n-butyl acrylate, t-butyl acrylate, hexyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, isobornyl acrylate, phenoxyethyl acrylate, decyl acrylate, and dodecyl acrylate; methacrylic acid esters of an alkyl alcohol (desirably a non-tertiary alcohol), wherein the alcohol contains from about 1 to about 14 (desirably from about 4 to about 14) carbon atoms and include, for example, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate and t-butyl methacrylate; (meth)acrylic acid monoesters of polyhydroxy alkyl alcohols such as 1,2-ethanediol, 1,2-propanediol, 1,3-propane diol, any of the various butyl diols, any of the various hexanediols, glycerol, such that the resulting esters are referred to as hydroxyalkyl (meth)acrylates; multifunctional (meth)acrylate esters, such as 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, glycerol diacrylate, glycerol triacrylate, and neopentyl glycol diacrylate; macromeric (meth)acrylates, such as (meth)acrylate-terminated styrene oligomers and (meth)acrylate-terminated polyethers; and (meth)acrylic acids and their salts with alkali metals, including, for example, lithium, sodium, and potassium, and their salts with alkaline earth metals, including, for example, magnesium, calcium, strontium, and barium.
Bifunctional monomers may also be used to prepare the (meth)acrylates suitable for use in the present invention. Typically, the bifunctional monomers possess at least one free radical and one cationically reactive functionality per monomer. Examples of such monomers include, but are not limited to, glycidyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl methacrylate and hydroxybutyl acrylate.
Epoxy: In one embodiment, the adhesive resin composition includes at least one epoxy resin. Epoxy resins useful in the present invention may be any organic compound having at least one oxirane ring, that is polymerizable by a ring opening reaction. Such materials, broadly called epoxides, include both monomeric and polymeric epoxides and may be, for example, aliphatic, alicyclic, heterocyclic, cycloaliphatic, or aromatic and may further be combinations thereof. Epoxides may be liquid or solid or blends thereof, blends being especially useful in providing tacky adhesive films. These materials generally have, on the average, at least two oxirane rings per molecule and may also be referred to as “polyepoxides.” The polymeric epoxides include, but are not limited to, linear polymers having terminal epoxy groups (for example, a diglycidyl ether of a polyoxyalkylene glycol), polymers having skeletal oxirane units (for example, polybutadiene polyepoxide), and polymers having pendent epoxy groups (for example, a glycidyl methacrylate polymer or copolymer). The molecular weight of the epoxy resin may vary from about 74 to about 100,000 or more. Mixtures of various epoxy resins may also be used in the structural adhesive composition of the bonding tape.
Suitable epoxy resins for use in the present invention include, but are not limited to, epoxy resins that contain cyclohexene oxide groups such as the epoxycyclohexane carboxylates, typified by 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, 3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methycyclohexane carboxylate, and bis(3,4-epoxy-6-methylcyclohexyl methyl)adipate.
Other epoxy resins that are particularly suitable for use in the present invention, include glycidyl ether monomers and have a structure as shown below:
where R′ is aliphatic, such as an alkyl group, aromatic, such as an aryl group, or combinations thereof; and n is an integer from about 1 to about 6. Examples of epoxy resins having a structure as shown in the formula above include, but are not limited to, the glycidyl ethers of polyhydric phenols obtained by reacting a polyhydric phenol with an excess of chlorohydrin such as epichlorohydrin, for example, the diglycidyl ether of 2,2-bis-(4-hydroxyphenol)propane (Bisphenol A). Desired epoxy resins include diglycidyl ethers of bisphenol A and hydrogenated bisphenol A-epichlorohydrin based epoxy resins.
Polyurethane: The adhesive resin composition may include, in one embodiment, at least one polyurethane resin. In the general reaction for the formation of a urethane, an isocyanate containing compound combines with a hydroxyl containing compound to create a urethane or carbamate linkage. The isocyanate containing compound may include aromatic, aliphatic, alicyclic and aromaticaliphatic isocyanates, such as tolylenediisocyanate, diphenylmethanediisocyanate, 3,3′-dimethyldiphenylmethane-4,4′-diisocyanate, naphthylene-1,5-diisocyanate, phenylenediisocyanate, xylylenediisocyanate, 1,6-hexamethylenediisocyanate, 1,4-tetramethylenediisocyanate, isophorone diisocyanate, hydrogenated tolylenediisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylenediisocyanate, dimers, trimers or biuret compounds of these diisocyanates, or adducts of compounds having active hydrogens therein to the isocyanates. A variety of compounds having active hydrogens therein are usable for the production of the adducts, and the compounds include polyols such as ethylene glycol, propylene glycol, tetramethylene glycol, neopentyl glycol, butanediol, 1,6-hexanediol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, trimethylolpropane, glycerine, pentaerythritol, castor oil, bisphenol A-ethylene oxide adducts or bisphenol A-propylene oxide adducts; and polyester polyols.
The polyester polyols may be produced by the reaction of a polybasic carboxylic acid (anhydride) with a polyhydric alcohol. The polybasic carboxylic acids (anhydrides) usable include, for example, maleic acid (anhydride), succinic acid (anhydride), adipic acid, fumaric acid, phthalic acid (anhydride), terephthalic acid, isophthalic acid, methyltetrahydrophthalic acid (anhydride), tetrahydrophthalic acid (anhydride), sebacic acid, dodecanedioic acid, azelaic acid, glutaric acid, trimellitic acid (anhydride), hexahydrophthalic acid (anhydride) and dimer acids. The polyhydric alcohol usable includes, for example, aliphatic glycols such as ethyleneglycol, propyleneglycol, butyleneglycol, hexyleneglycol, decanediol or neopentyl glycol; aliphatic polyether glycols such as diethyleneglycol or dipropyleneglycol; and others such as glycerine, trimethylolpropane, 1,4-cyclohexanedimethanol, neopentyl glycol ester of hydroxypivalic acid, 1,4-cyclohexanediol or hydrogenated bisphenol A.
In one embodiment, the compound containing isocyanate functionalities may be a polyurethane prepolymer having the general formula:
R(OCONHXCO)_n
where n=2 to 4, R is selected from the group consisting of alkyl, alkenyl, aliphatic ether, aliphatic ester, aromatic ester, and mixed aliphatic ester and aromatic ester, and X is an aromatic diisocyanate or polyisocyanate based upon methylene dianiline diisocyanate, its isomers, homopolymers, oligomers and mixtures thereof. In one aspect of the invention, the polyurethane prepolymer may be prepared by reacting a hydroxy-terminated polyol with a mixture of diisocyanates and polyisocyanates, in the presence of an excess of the mixture of diisocyanates and polyisocyanates, until all of the hydroxyl groups on the hydroxy-terminated polyol have reacted.
In another aspect of the invention, the polyurethane prepolymer may be fully polymerized, having the general formula:
R(OCONHXNHCOOR¹)_n
where n=2 to 4, R is selected from the group consisting of alkyl, alkenyl, aliphatic ether, aliphatic ester, aromatic ester, and mixed aliphatic ester and aromatic ester, R¹is as defined for R, and X is a diisocyanate or polyisocyanate based upon methylene dianiline diisocyanate, its isomers, homopolymers, oligomers and mixtures thereof.
The hydroxyl containing compounds may contain from about 2 to about 5 hydroxy functional groups. The hydroxy functionality may be positioned anywhere on the hydroxy-containing compound. In one embodiment, the hydroxy-containing compound is hydroxy-terminated. Examples of hydroxy-terminated compounds include diols and triols containing from 2 to 10 carbon atoms, polyethers, polyesters, and polybutadiene polyols.
In addition to the UV curable resin, the adhesive composition includes one or more photoinitiators, which are exemplified by benzoin compounds such as benzoin, benzoin methylether, benzoin ethylether, benzoin isobutylether or benzoin octylether; and carbonyl compounds such as benzil, diacetyl, diethoxyacetophenone, 2-hydroxy-2-methylpropiophenone, 4′-isopropyl-2-hydroxy-2-methylpropiophenone, methylanthra-quinone, acetophenone, benzophenone, methyl benzoylformate, benzil methyl ketal or 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-(4-(methylthio)phenyl)-2-morpholino)propene-1, onium salts and cationic organometallic salts. Various other additives may be included in the adhesive composition, such as fillers, stabilizers, plasticizers, tackifiers, flow control agents, cure rate retarders, adhesion promoters, adjuvants, impact modifiers, fire retardants, expandable microspheres, thermally conductive particles, electrically conductive particles and the like.
The adhesive resin impregnated fiber reinforced fabric may be provided with an opaque, non-stick overlay film adhered to the fabric. The overlay film may include a silicone coated paper or polymeric film. Depending on the tack level of the specific adhesive, a polyethylene overlay film may be used.
The bonding tape may include a variety of layers and adhesive components as described above. In one embodiment, the bonding tape includes a single adhesive layer and an opaque overlay film on an outer surface of the adhesive layer.
In FIG. 4, an example of this bonding tape is shown. The bonding tape 70 includes an adhesive layer 71 containing fiber reinforcement fabric 72, and an opaque overlay film 73 on the outer surface 74 of the adhesive layer 71. When in roll form, exposed surface 76 of the adhesive layer 71 comes into contact with the outer surface 75 of the overlay film 73.
Referring to FIGS. 5A and 5B, the method of joining two adjacent composite panels with a bonding tape is illustrated. A first panel 81 is joined to a second panel 82 at seam 83. A length of bonding tape 60 is adhered to the outer surface 81 a of panel 81 and outer surface 82 a of panel 82 over the seam 83 so that the opaque overlay film 63 faces outward. The overlay film 63 is removed to expose the underlying adhesive resin 61 of the impregnated reinforcement fabric. The adhesive resin 61 of the exposed fabric is cured by application of a UV light source 85 to the adhesive surface 64. The UV light source 85 may be a UV lamp or may be sunlight. Once the adhesive layer is cured, a solid structural connection 65 between the first panel 81 and the second panel 82 is formed. A second length of bonding tape (not shown) may be applied to the opposite outer surface 81 b of the first panel 81 and the opposite outer surface 82 b of the second panel 82 over the seam 83 to form a second structural connection between the first panel 81 and the second panel 82.
FIG. 6 illustrates a seam between two joined composite panels. A first panel 81 is joined to a second panel 82 at seam 83. A length of cured bonding tape 84 is positioned over the seam 83 on the outer surface 81 a on first panel 81 and outer surface 82 a, and forms a structural bond between first panel 81 and second panel 82.
FIG. 7 illustrates a corner joint of two joined composite panels, the first planar panel 91 in a first plane x, and the second planar panel 92 in a second plane y that is perpendicular to the first plane. A length of cured bonding tape 94 is positioned over the corner joint seam 93 on the outer surface 91 a on first panel 91 and outer surface 92 a, and forms a structural bond between first panel 91 and second panel 92. Although the panels 91, 92 are shown joined at an angle of 90 degrees (90°), the angle may be a different angle, e.g., an obtuse angle or an acute angle. Also, although the tape 84 in FIG. 6 and the tape 94 in FIG. 7 are shown at one surface of the jointed panels at the respective joints 83, 93, it will be appreciated that the tape may be at the other surface or at both surfaces of the respective panels at the joint thereof.
The present invention is directed, in one embodiment, to a method of making structural connections between foam cored composite panels for fabrication of architectural structures, such as a house, warehouse, barn, shed or other architectural edifice. The method may involve the use of a resin-preimpregnated fiberglass fabric or other fibrous structural tape which is precut and dispensed in the form of a roll or packaged lengths of such tape. The resin used for impregnation in the tape does not cure unless exposed to sunlight or ultraviolet light source. The tape may be factory formed as a co-laminate with an opaque polyfilm barrier which is transported and later dispensed at the construction site with the impregnated fabric tape. When the opaque film is peeled off by workers at the jobsite, light is then allowed to cause the resin to cure and the two adjacent composite panels adhered by such tape will be permanently bonded together in a structural connection. Corner joints, panel seams, butt joints and roof seams can be adhesively bonded together by use of such tape to form a watertight, weatherproof solid structural connection which provides full structural continuity between connected panels for the life of the building.
The resin is thickened sufficiently so that it does not flow out of the fabric before use, but is sufficiently liquid to allow the adhesively bonded composite panels to be wetted to effect a chemical or adhesive bond between them, the tape and the connected composite panel.
Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings.

Claims

1. A joint connecting a first sandwich panel and a second sandwich panel, the joint comprising:

a first sandwich panel having a first outer layer and a second outer layer spaced from the first outer layer by a panel core, and an edge comprised of an edge portion of the panel core, an edge portion of the first outer layer and an edge portion of the second outer layer;

a second sandwich panel having a first outer layer and a second outer layer spaced from the first outer layer by a panel core, and an edge comprised of an edge portion of the panel core, an edge portion of the first outer layer and an edge portion of the second outer layer, wherein the edges of the sandwich panels are in contact with one another at an interface between the panels; and

a structural bond formed at the interface on the first outer surfaces of the panels, the structural bond comprising a layer of structural adhesive material and at least one reinforcement fabric of fibers at least partially embedded within the layer of adhesive material, wherein the structural adhesive layer is cured upon exposure to ultraviolet radiation.

2. The joint of claim 1 wherein the layer of adhesive material comprises at least one UV curable resin chosen from (meth)acrylates, epoxy, polyurethanes, vinyl esters, polyester, phenolic, silicone resins, and mixtures of two or more thereof.

3. The joint of claim 1 wherein the layer of adhesive material comprises at least one UV curable (meth)acrylate resin.

4. The joint of claim 1 wherein the reinforcement fabric of fibers is chosen from fiberglass mesh, woven fabrics, non-woven fabrics, knitted fabrics and a unidirectional array of fibers.

5. The joint of claim 1 wherein the fibers of the reinforcement fabric are chosen from polyester, polyolefin, aramid, cotton, sisal, jute, hemp, glass, carbon, ceramic, and coated fibers having a core component and a coating thereon.

6. The joint of claim 1 wherein the reinforcement fabric of fibers comprises a fiberglass mesh.

7. The joint of claim 1 further comprising a second structural bond formed at the interface on the second outer surfaces of the panels, the structural bond comprising a layer of structural adhesive material and at least one reinforcement fabric of fibers at least partially embedded within the layer of adhesive material, wherein the structural adhesive layer is cured upon exposure to ultraviolet radiation.

8. A method of joining sandwich panels comprising:

providing a first sandwich panel having a first outer layer and a second outer layer spaced from the first outer layer by a panel core, and an edge comprised of an edge portion of the panel core, an edge portion of the first outer layer and an edge portion of the second outer layer;

providing a second sandwich panel having a first outer layer and a second outer layer spaced from the first outer layer by a panel core, and an edge comprised of an edge portion of the panel core, an edge portion of the first outer layer and an edge portion of the second outer layer;

contacting the edges of the sandwich panels with one another at an interface between the panels;

applying a bonding tape to the interface on the first outer surfaces of the panels, the bonding tape having an inner surface and an outer surface and comprising a layer of ultraviolet curable structural adhesive material and at least one reinforcement fabric of fibers at least partially embedded within the layer of adhesive material; and

exposing the adhesive material to a source of ultraviolet radiation to form a structural bond between the first panel and the second panel at the interface.

9. The method of claim 8 wherein the layer of adhesive material comprises at least one UV curable resin chosen from (meth)acrylates, epoxy, polyurethanes, vinyl esters, polyester, phenolic, silicone resins, and mixtures of two or more thereof.

10. The method of claim 8 wherein the layer of adhesive material comprises at least on UV curable (meth)acrylate resin.

11. The method of claim 8 wherein the reinforcement fabric of fibers is chosen from fiberglass mesh, woven fabrics, non-woven fabrics, knitted fabrics and a unidirectional array of fibers.

12. The method of claim 8 wherein the fibers of the reinforcement fabric are chosen from polyester, polyolefin, aramid, cotton, sisal, jute, hemp, glass, carbon, ceramic, and coated fibers having a core component and a coating thereon.

13. The method of claim 8 wherein the reinforcement fabric of fibers comprises a fiberglass mesh.

14. The method of claim 8 wherein the source of ultraviolet radiation is sunlight.

15. The method of claim 8 wherein the bonding tape further comprises an opaque overlay film on the outer surface.

16. The method of claim 15 wherein the opaque overlay film is removed prior to exposure to ultraviolet radiation.

17. An architectural edifice comprising the joint of claim 1.

18. An architectural edifice made according to the method of claim 8.