Carbon fiber re-enforced composite sheet piling segments

Abstract

A carbon fiber re-enforced composite segment of sheet piling has been developed. The segment of sheet piling includes a base material and carbon fibers that re-enforce the base material. Other fiber materials could be used in place of carbon. These materials include: aramid, kevlar, metal cords, and basalt. Additionally, a mixture of any of these types of materials could be used as a fiber re-enforcement for the sheet piling segment.

Description

BACKGROUND OF INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates generally to the composition of building materials. More specifically, the invention relates to fiber re-enforced sheet piling segments.

[0004] 2. Background Art

[0005] Sheet piling is a construction material that is commonly used to build walls for the purpose retaining soil or water such as retaining sea-walls. The sheet piling is typically manufactured in individual segments that are attached to other segments to form a continuous wall. Since the segments are usually driven into the ground for stability, the segments may be several meters tall.

[0006] Sheet piling was once commonly made with steel or other metals. However, such piling may now be made with fiber re-enforced polymers (FRP). FRPs are formed out of a cured resin that has been re-enforced with fibers made of materials such as glass. The resin typically may be polyester or vinylester. While not as strong as steel, these materials offer better performance due to resistance to corrosion and other effects of chemical environments. Steel is an example of an “isotropic” material in that loads are distributed equally through out the material. In contrast, FRPs are generally considered “anisotropic” in that loads are not distributed equally in the material. For example, a composite material such as fiberglass is stronger along the orientation of the glass fibers than in other areas of the material.

[0007] While the FRP materials are resistant to corrosion, they will absorb water when exposed to that environment for long periods of time. This is a particular problem when sheet piling made from FRPs is used to build a seawall. If the sheet piling is exposed long enough and absorbs enough water, the structure may become weakened to the point of failure. Additionally, when FRP sheet piling is used to build a seawall, it also is exposed to active pressure from soil on one side of the wall while being exposed to a passive pressure from the water on the other side. Over time, the panels of material can weaken and the panels may deform or fail catastrophically under this type of pressure alone or combined with any weakening of the material from water absorption.

[0008] The potential for such failures are particularly acute at the joints that join the panels together and at any corner or edge of a panel. According to modeling, maximum tension occurs at the corner angles of the panels. Typical solutions involved re-enforcing points of potential failure on a panel of sheet piling with a concave shaped re-enforcement. However, these re-enforcements have proven insufficient to provide the additional strength to a panel made of anisotropic materials (such as FRPs).

SUMMARY OF INVENTION

[0009] In some aspects, the invention relates to a segment of sheet piling, comprising: a base material; and carbon fibers that re-enforce the base material. In other aspects, the invention relates to a segment of sheet piling, comprising: a base material; and aramid fibers that re-enforce the base material. In other aspects, the invention relates to a segment of sheet piling, comprising: a base material; and kevlar fibers that re-enforce the base material. In other aspects, the invention relates to a segment of sheet piling, comprising: a base material; and basalt fibers that re-enforce the base material.

[0010] In other aspects, the invention relates to a segment of sheet piling, comprising: a base material; and a mixture of fibers that re-enforce the base material, where the mixture of fibers comprises at least two types of materials; and where the materials of the mixture of fibers are selected from the group consisting of: carbon, aramid, kevlar, basalt, or glass

[0011] In other aspects, the invention relates to a segment of sheet piling, comprising: a base material; and means for re-enforcing the base material with a fiber material.

[0012] Other aspects and advantages of the invention will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

[0013] It should be noted that identical features in different drawings are shown with the same reference numeral.

[0014] FIG. 1 shows an overhead view of two joined sheet piling segments in accordance with one embodiment of the present invention.

[0015] FIG. 2 shows an overhead view of a re-enforced corner of a sheet piling segment in accordance with one embodiment of the present invention.

[0016] FIG. 3 shows and overhead view of a joint of two joined sheet piling segments in accordance with one embodiment of the present invention.

[0017] FIGS. 4 a and 4b show views of re-enforcing wire in accordance with some embodiments of the present invention.

[0018] FIGS. 5 a and 5b show views of woven patterns of re-enforcing material in accordance with some embodiments of the present invention.

DETAILED DESCRIPTION

[0019] FIG. 1 shows an overhead view of two joined sheet piling segments 10a and 10b in accordance with one embodiment of the present invention. The two sheet piling segments or “sheets” shown are typically used in construction of seawalls in either freshwater or saltwater environments. In the present embodiment, each sheet 10a and 10b is made of three distinct panels 12 that are roughly configured in a “Z” shaped arrangement. Each panel fits with adjacent panels to form a corner 14 of the segment. The panels 12 form an angle of approximately 120° at each corner 14. In alternative embodiments, the number of panels in a segment of sheet piling may vary along with their relative angles to each other.

[0020] The two segments 10a and 10b are connected at a joint. One panel 10a has a male joint attachment 16, while the other panel 10b has a female joint attachment 18. These two attachments 16 and 18 fit together to form the joint that interlocks the segments 10a and 10b. Multiple segments are fitted together to form a length of wall. In this embodiment, each segment has a male joint attachment 16 and a female joint attachment 18 on alternative ends of the segment. In alternative embodiments, segments may have two male attachments or two female attachments.

[0021] If the segments are used to construct a seawall, forces are exerted on the panels 12 and the joint on one side by soil and on the other side by water. In the present embodiment, the segments 10a and 10b are re-enforced along the panels 20 and the corners 22 in order to prevent the segments from bulging at these points and potentially failing catastrophically. The panel re-enforcement 20 has a circular cross-section and is centered on the panel 12. An overhead view of the corner re-enforcement 22 is shown in FIG. 2 in accordance with one embodiment of the present invention. The re-enforcement 22 is centered on the corner 14 of the two panels 12 of the sheet piling segment. Re-enforcing this area of the corner 14 helps prevent the panels 12 from bulging outward and compromising the integrity of the corner 14. The re-enforcement 22 has a convex cross-sectional shape that maximizes the re-enforcement strength for the corner while optimizing the use of materials to manufacture the sheet. A re-enforcement with a convex cross-sectional shape is particularly suited for used with anisotropic materials such as FRPs. A convex re-enforcement helps prevent rupturing of a matrix of fibers in the material.

[0022] In order to prevent separation of the sheet piling segments 10a and 10b at the joint, the male joint attachment 16 is re-enforced between the attachment 16 and its panel 12. An overhead view of the male joint attachment re-enforcement 24 is shown in FIG. 3 in accordance with one embodiment of the present invention. The re-enforcement 24 is centered between the panel 12 and the male attachment 16. Re-enforcing this area of the attachment 16 helps prevent twisting and buckling of the male attachment 16 that would result in its separation from the female attachment 18. The re-enforcement 24 has a triangular cross-sectional area that maximizes the re-enforcement strength of the attachment 16 while optimizing the use of materials. A triangular shaped re-enforcement 24 is used due to the 90° angle between the panel 12 and the bottom of the male attachment 16.

[0023] In some embodiments, the dimensions of the sheet may be 18 inches long (i.e., the linear length from the male attachment to the female attachment of a segment) and 8 inches wide (i.e., the linear distance between the two end panels of the segment). The segment may have a height of several feet or longer. The thickness of a panel of the segment may be 0.25 inches. In alternative embodiments, these dimensions may vary accordingly.

[0024] The segment of sheet piling may be made of polyurethane material. Polyurethane is a material with hydrophobic properties of low water absorption, even when the outer skin has been breached (e.g., by drill holes). The material is also highly impact resistant and stable under prolonged exposure to ultra-violet (UV) radiation and saltwater. In typical applications, polyurethane may be “heat cured”. Curing is a chemical process where a liquid material (e.g., a resin) crosslinks to form a solid. The curing process may be initiated or accelerated by the application of heat. It is commonly done during the molding process and may take a few seconds to a few hours for completion depending on the materials involved.

[0025] Polyurethane elastomers are one member of a large family of elastic polymers called rubber. Polyurethane may be a liquid that can be molded into any shape or size. It is formed by reacting a polyol (an alcohol with more than two reactive hydroxyl groups per molecule) with a diisocyanate or a polymeric isocyanate in the presence of suitable catalysts and additives. The chemical formula for polyurethane is: C3H8N2O. A wide variety of diisocyanates and polyols can be used to produce polyurethane in alternative embodiments. It should be understood that the term “polyurethane” includes a wide variety of thermoplastic polyurethane elastomers that are manufactured differently and may have different performance characteristics.

[0026] In an alternative embodiment, polyurethane may be used as a base component of a multi-component mixture. Such a multi-component material includes: a hardening catalyst such as isocyanate and a resin such as polyurethane. The advantage of a multi-component mixture is that it does not require heat during the curing process. In alternative embodiments, alternative materials could be used that are suitable as a hardening catalyst and a resin. For example, a castor oil-based catalyst may be used to help the chemical reaction that hardens the materials. Additionally, a castor oil-based catalyst greatly reduces the tendency of the segment to absorb water.

[0027] In an alternative embodiment, a polyurethane based material (either alone as a single component material of polyurethane or in a multi-component material) is used with re-enforcing fibers to form the sheet piling segments. The segments are manufactured by a process called “pultrusion”. With the pultrusion process, the fibers are pulled through a wet bath of polyurethane resin. The fibers are wetted with polyurethane by the bath. The wet fibers are then cast into a matrix to increase the structural strength of the segment. The matrix may be a woven pattern whose design may vary to increase the strength of the finished product. The material is then pulled through a die where the segment of sheet piling is formed. The segment is then heat cured to solidify the polyurethane and complete the manufacture of the segment. The fibers used in the process may be made of glass, carbon, or other suitable material that provides strength to the material.

[0028] In alternative embodiments, the segments may be manufactured by a process called “extrusion”. With the extrusion process the matrix or “mat” of woven fibers is positioned in a mold and the vinyl material is extruded or pushed through a cross-head die to form the composite material. The cross-head die is typically located at a 90° angle from the threads so that the extruded vinyl is injected across the fibers.

[0029] In an alternative embodiment, sheet piling segments may be made of standard FRP materials with a water-resistant gel coating applied to the surface of the piling. The gel-coating will prevent absorption of water by the underlying FRP material and consequently prevent weakening of the integrity of the sheet piling segment. An example of a suitable material for use as a gel coating is a “neopental isothalic acid resin” system. This material protects FRPs from water absorption while it also resists barnacles and other parasites. In other embodiments, other suitable water-resistant materials could be applied to the surface of the FRP to prevent water absorption.

[0030] Sheet piling segments, as shown in FIGS. 1-3, may be re-enforced with the addition of carbon fibers to their material composition. The carbon fibers have the advantages of adding strength and stiffness to the segment while still being lightweight (i.e., a high strength to weight ration). Other advantages include good chemical corrosion resistance and low moisture absorption. The fibers may be used as fiber re-enforcement in both polyurethane based sheet piles and FRP sheet piles (with or without the water-resistant gel coating). The fibers may be formed into a woven pattern or “mat” that is layered or stacked in the die to form the sheet piling segment. This allows the woven patterns of fiber to be concentrated in areas of a sheet pile that need re-enforcement such as corners 22 (shown in FIG. 2) and in the joint connection of a male joint attachment 16 and a female joint attachment 18 (shown in FIG. 3). In some embodiments, supplement fiber re-enforcement can be added only at the joint or only at the corner of the sheet pile segment. In other embodiments, fiber re-enforcement can be added for the entire sheet pile segment with additional supplemental fibers added at the joint or the corner as desired for increased strength. The fiber re-enforcement can be added in place of or in addition to the convex and triangular shaped re-enforcements discuss previously.

[0031] The carbon fibers are typically produced by the pyrolysis of organic precursor fibers, such as rayon polyacrylonitrile (PAN) and pitch in an inert environment. The term carbon may also be used to include graphite materials. The fiber content of the sheet pile material may range from anywhere from 1 to 70 percent by volume. The greater the percent of fiber, the greater the strength level for a specific weight. In alternative embodiments, other suitable fiber materials may be used instead of carbon. Examples of such suitable fiber materials include: aramid fibers, kevlar fibers, and basalt fibers. Additionally, these fiber materials may be used as alone or in combination with other types of fibers including glass fibers that are known in the prior art.

[0032] In other embodiments, cords made of metal wire may be used as re-enforcements in place of or in addition to fiber materials. The wires may be made of steel, aluminum, brass, copper, or other suitable metals. Also, combinations of metals or alloys may be used depending on such factors as strength, weight, cost, adhesive properties, etc. The re-enforcing cords may be formed with of a series of twisted wire wires to provide additional strength. Examples of twisted wires are shown in FIGS. 4a and 4b. As shown in FIG. 4b an additional wire 32 may wrapped around a plurality of twisted wires that form a central bundle 30 of the re-enforcing cord. In the examples shown in FIGS. 4a and 4b, the wires have a diameter of 0.20-0.22 mm and a cord diameter of 0.35 inches.

[0033] The re-enforcing wires may be woven together in a pattern as shown in FIGS. 5a and 5b. FIG. 5a shows a low density (4 cords/inch) open weave pattern. A low density pattern (4 cords/inch) or a medium density pattern (12 cords/inch) are typically used with resins or other materials that have a high viscosity so as to have better penetration of the mat. FIG. 5b shows a high density (22 cords/inch) weave pattern that is with very low viscosity materials. The weave patterns or “mats” as shown in FIGS. 5a and 5b are typically made in rolls. Portions of the roll may be cut and fitted into a mold for sheet piling as a re-enforcement for a joint, a corner, or for the entire sheet panel. Supplemental segments of the mat may be layered on the joint or corner to provide additional re-enforcement as described previously.

[0034] While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed here. Accordingly, the scope of the invention should be limited only by the attached claims.

Claims

1. A segment of sheet piling, comprising: a base material; and carbon fibers that re-enforce the base material.

2. The segment of sheet piling in claim 1, where the base material is polyurethane.

3. The segment of sheet piling in claim 1, where the base material is a polymer material.

4. The segment of sheet piling in claim 1, where the carbon fibers comprise 1-70 percent of the volume of the segment of sheet piling.

5. A segment of sheet piling, comprising: a base material; and aramid fibers that re-enforce the base material.

6. The segment of sheet piling in claim 1, where the base material is polyurethane.

7. The segment of sheet piling in claim 1, where the base material is a polymer material.

8. The segment of sheet piling in claim 1, where the aramid fibers comprise 1-70 percent of the volume of the segment of sheet piling.

9. A segment of sheet piling, comprising: a base material; and kevlar fibers that re-enforce the base material.

10. The segment of sheet piling in claim 1, where the base material is polyurethane.

11. The segment of sheet piling in claim 1, where the base material is a polymer material.

12. The segment of sheet piling in claim 1, where the kevlar fibers comprise 1-70 percent of the volume of the segment of sheet piling.

13. A segment of sheet piling, comprising: a base material; and basalt fibers that re-enforce the base material.

14. The segment of sheet piling in claim 1, where the base material is polyurethane.

15. The segment of sheet piling in claim 1, where the base material is a polymer material.

16. The segment of sheet piling in claim 1, where the basalt fibers comprise 1-70 percent of the volume of the segment of sheet piling.

17. A segment of sheet piling, comprising: a base material; and a mixture of fibers that re-enforce the base material, where the mixture of fibers comprises at least two types of materials; and where the materials of the mixture of fibers are selected from the group consisting of: carbon, aramid, kevlar, basalt, metal cords, or glass.

18. A segment of sheet piling, comprising: a base material; and means for re-enforcing the base material with a fiber material.

19. A segment of sheet piling, comprising: a base material; and metal cords that re-enforce the base material.

20. The segment of sheet piling in claim 19, where the base material is polyurethane.

21. The segment of sheet piling in claim 19, where the base material is a polymer material.

22. The segment of sheet piling in claim 19, where the metal cords comprise a plurality of twisted wires.

23. The segment of sheet piling of claim 19, where the metal cords are woven into a mat.

24. A segment of sheet piling, comprising: a base material; and means for re-enforcing the base material with metal cords.