Patent Application
20050118369
The present invention relates to structural sandwich plate members, which plate members comprise outer plates bonded together by a core layer of plastics or polymer material which transfers shear forces therebetween, and to structures formed by connecting together structural sandwich plate members.
Structural sandwich plate members, known commercially as SPS™, are described in U.S. Pat. No. 5,778,813, British Patent Application GB-A-2 337 022 and International Application No. GB00/04198 which documents are incorporated herein by reference. Such structural sandwich plate members comprise outer metal plates bonded together by a plastics or polymer core with sufficient strength to transfer shear forces therebetween. The plastics or polymer core may be solid and continuous, occupying the entire volume between the outer metal plates, or may be interrupted by, e.g. foam, forms which leave continuous plastics or polymer connections between the outer metal plates. A principal use of these structural sandwich plate members is to replace stiffened steel structures, e.g. in maritime, offshore and civil engineering applications. In such applications, the structural sandwich plate members enable the elimination of some or all stiffening elements providing a simpler structure that is easier to construct and maintain. In particular, the amount of welding necessary is generally substantially reduced as compared to a conventional stiffened steel structure.
A further advantage of such structural sandwich plate members is that they can be prefabricated, either as individual plate members or as more complex modules to be assembled into the eventual structure. Pre-fabricated modules can be made under factory conditions to greater accuracy than traditional structures, can be assembled on site and further ease construction.
Although such structural sandwich plate members have considerable technical and economic advantages over traditional stiffened steel structures, their weight is comparable to, or moderately less than that of traditional stiffened steel structures and a considerable amount of steel or metal is still present, which can be undesirable in some applications.
It is an aim of the present invention to provide alternative forms of structural sandwich plate members, preferably with lower weight than those made with all metal face plates and having other improved properties.
According to the present invention, there is provided a structural sandwich plate member, comprising first and second face plates and a plastics or polymer core bonding said face plates together with sufficient strength to transfer shear forces therebetween, at least one of said face plates being formed of a non-metal reinforced composite or reinforced polymer material.
A structural sandwich member with one non-metal face plate can provide improved chemical resistance and is advantageous for use in forming storage tanks, with the non-metal face plate on the inside. If both face plates are made of non-metal material, a metal free structure, having reduced electromagnetic signature can be made.
The non-metal face plates are preferably made of a fiber-reinforced polymer material such as carbon-fiber reinforced polymer material. The strengths and like properties of such composite materials are often specified as a ratio whereby the value of the property in other units is divided by the density of the material. In the invention, the strength ratio of the face plates (tensile strength/density) is preferably in the range of from 0.03 to 0.5, most preferably 0.1 to 0.25 (MPa/kgm−3). Similarly, the stiffness ratio (modulus of elasticity/density) is preferably in the range of 0.5 to 50, most preferably 2 to 26 (MPa/kgm−3).
The structural sandwich plate members according to the invention are particularly advantageous for use in applications where extremely low weight is required or steel and other metals are undesirable. For example, the structural sandwich plate members according to the invention may be used in mine sweepers and other specialist military vessels for which a low electromagnetic signature or a reduction in ship/structure borne noise is desirable. Civil engineering applications for the invention include bridge deck panels and chemical tanks. For bridge deck panels, the weight savings can provide a substantial reduction in the cost of the superstructure supporting the deck and the non-metal face plates provide a structure that is resistant to corrosive road salts. For chemical storage tanks, one or both face plates can be made of a material chosen to resist chemical attack from the stored chemical.
The present invention also provides structures comprising at least one structural sandwich plate member as described above.
Further, the present invention provides a method of manufacturing a component of a structure comprising the steps of:
Yet further, the present invention provides a method of reinforcing an existing metal structure comprising the steps of:
This method can be used for the repair or rehabilitation of an existing metal, e.g steel, structure that has deteriorated due to age, corrosion or wear. The reinforcing layer reinstates the structural capacity of the existing structure and inhibits further deterioration. The light weight reinforcing layer may be shaped or formed off-site or in-side to fit the shape of the existing structure, including any reinforcing elements. The reinforcing layer may be made of, or include, a layer of ceramic material to provide enhanced fire resistance. The method of the present invention can be applied simply in confined or dangerous areas, e.g. the interior of storage tanks, using prefabricated sections to avoid hot work on site.
The present invention will be further described below with reference to the following description of exemplary embodiments and the accompanying drawings, in which:
In the drawings, like parts are indicated by like references.
The structural sandwich plate member 1 comprises outer face plates 11 and 13 which are bonded together by core 12. The face plates 11, 13 are made of a carbon-fiber reinforced plastics material whilst the core 12 is made of a plastics or polymer material such as polyurethane. The core 12 is preferably compact, i.e. not foamed, though a certain amount of cavitation may be permitted in some applications. The core 12 is integrally bonded to the face plates 11, 13 providing continuous support and sufficient shear and bond strength to transmit the expected shear loads between them. The thicknesses of the sandwich elements 11, 12, 13 are selected to provide the flexural and in-plane strength and stiffness of the sandwich plate for the particular static and dynamic requirements The strength and stiffness ratios for the non-metal reinforced composite plates are expressed as the ratio of the tensile strength divided by the mass density; and the ratio of the modulus of elasticity divided by the mass density and are in the range of 0.03 to 0.95, preferably 0.1 to 0.25 (MPa/kgm−3); and 0.5 to 50, preferably 2 to 26 (MPa/kgm−3) respectively, for use in maritime, offshore and civil engineering structures. It will be appreciated that the dimensions of the member will vary according to application but for practical maritime and civil engineering applications the face plates may have thicknesses T1, T3 in the range of from 1 to 30 mm and the core a thickness T2 in the range of from 10 mm to 150 mm. The thicknesses of the two face plates may be different and may vary across their area. Similarly, the thickness of the core may vary across the area of the plate member. Although the plate member 1 is shown in
In a second embodiment of the invention, a structural sandwich plate member 1a shown in cross section in
To increase the strength of the element, transverse shear plates 17 extending between the face plates 11, 13 may also be provided. Such shear plates are preferably perforated to improve bonding between the core 12 and the shear plates 17. The shear plates 17 assist in transfer of shear forces between face plates 11, 13.
To manufacture the structural sandwich plate member according to the invention, the face plates 11, 13 are placed in a spaced apart relationship, either in a mold or with edge members (not shown) spanning between them, to form a closed cavity. The cavity is then injected with material to form the core 12. Of course, internal elements such as those shown in
As shown in
As seen in
The members 30 are prefabricated off-site in long lengths, then cut as necessary and shipped to the construction site. On-site they are assembled into the desired structure, which may involve further trimming, and once in place, plastics or polymer is injected to form the core 12. In this way, dimensional accuracy can be assured by off-site manufacture and handling is facilitated on-site because the members are very light and easy to cut before the core 12 is injected. When the core is injected, the members achieve full structural strength.
In
According to the invention, a reinforcing layer 24, 25 is positioned in a spaced apart relationship to the plate to be repaired, in this case bottom plate 21. Spaces, such as elastomer stubs, may be used to ensure the desired spacing. The reinforcing layer is made of a reinforced composite or reinforced polymer material as in the previous embodiments. It may be provided in prefabricated sections of standard forms, or continual sections for a specific job, which are fitted around the reinforcing elements 22, 23, 28. In the present example, the bulb flats 22, 23, are enclosed by the reinforcing layer but the girders 28 project through, Sections 24, 25 of the reinforcing layer make rolled lap joints to the girder 28. Where necessary, the sections can be cut to size with a jig-saw and can be joined by suitable adhesive or by bolting 26 to a bulb flat.
Once the reinforcing layer 24, 25 has been completed, plastics or polymer material is injected into the casing between reinforcing layer 24, 25 and plate 21 and cured to form core layer 27. The core layer 27 bonds the reinforcing layer and plate 21 together with sufficient strength to transfer shear forces expected in use and thus forms a composite structural whole.
With this invention, no significant heat is generated during the repair process so that only the compartment being worked in, and not neighbouring compartments, needs to be flushed of flammable vapours.
The method can also be applied to pipelines using molded or pultruded overlay sections with snap interlocking longitudinal seams and prefabricated ring perimeter sections.
Whilst embodiments of the present invention and possible uses for them have been described, it will be appreciated that the connecting member of the present invention may be constructed differently than as described and may be used in other ways, as will occur to the skilled reader. The present invention is not to be limited save within the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0201903.2 | Jan 2002 | GB | national |
This is a U.S. national phase application under 35 U.S.C. §371 of International Patent Application No. PCT/GB03/00225 filed Jan. 17, 2003, and claims the benefit of Great Britian Patent No. 0201903.2 filed Jan. 28, 2002 which is incorporated by reference herein. The International Application was published in English on Aug. 7, 2003 as WO 03/064154 A1 under PCT article 21(2).
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB03/00225 | 1/17/2003 | WO |
