SPECIFICATION BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The present invention relates to the field of bridges and more particularly, to a method and apparatus for providing a fiberglass bridge system and includes a method of molded core lay-up.

DESCRIPTION OF THE PRIOR ART

For many decades steel and concrete have been used to construct bridges. However, the infrastructure around the world and, in particular, the United States, is in serious disrepair. Within the United States more than 180,000 traditional steel and/or concrete secondary road bridges must be immediately repaired or replaced at an estimated cost of $4.5 Billion. In addition to the cost, road use is lost for a period of months while traditional bridges are removed and replaced.

Steel and concrete bridges are subject to deterioration due to environmental conditions. Deterioration of these traditional bridges begins immediately. This type of bridge is supposed to have a life span of twenty-five years. The actual life span is twelve to twenty years depending on existing conditions. Further, during the life of the bridge much repair must be done. Repainting of the bridge is generally required within three years of installation. Concrete work to repair deterioration is generally required within seven years.

A need exists for a bridge that is made of non-biodegradable material that is stronger, lighter, more flexible, less expensive and impervious to environmental deterioration. To replace an _d

install a traditional concrete and steel bridge is built on location and the road is closed during the construction period. Therefore, there is a need for a bridge system that can be easily fabricated and installed in a manner that does not prevent use of a road for a period of months.

The previous efforts in this area have not successfully developed such a bridge. These previous efforts include:

Melcher, U.S. Patent No. 3,328,818, discloses a reinforced walk ramp constructed from a sheet of relatively thin plywood reinforced along its bottom surface by longitudinal beams constructed to resist co pressive and tensil forces. The walk ramp is of a unitary construction by which fibrous glass reinforced resin beams are integrally bonded to a sheet of suitable surfacing material along the length thereof. The sheet includes a resin coating on its upper surface having an imbedded friction material for traction and wear resistance. The sides include a core of plywood or other material covered by a glass fiber reinforcing mat and resin.

Prusinski, et al, U.S. Patent No. 3,494,086, discloses a panel construction and method of making a panel for a building wall comprising at least two matrix layers of a filled resinous material. A foraminous sheet is provided at the interface of the layers. A mass of rigid foamed material is encased by the layers. At least one translucent block having a thickness less than the panel thickness is completely surrounded by the matrix layers. The foamed material acts as an inexpensive fill, as insulation and as a panel lightener.

Zwilcrmever, U.S. Patent No. 4,453,357, discloses a wall structure comprising a core of rigid plastic foam coated on one side with a layer of non-expanded plastic. The structure has an elongated shape with opposite side surfaces having respective groove-and-tongue-like surfaces for engagement with adjoining members. A reinforced plastic mat which sets in a continuous layer may be applied to the other side of the core after attachment of

the cores.

Green, U.S. Patent No. 4,029,172, discloses a fiberglass ladder comprising a pair of rails and a plurality of rungs each having a continuous layer of fiberglass extending along its length. The ladder is constructed in a mold by laying the fiberglass filaments in the bottom of the channels of the mold on top of woven fiberglass and a resin layer. The channels are then filled with a rigid plastic foam, and a ladder is allowed to cure. The outer surface of the ladder is a layer of resin, normally called gelcoat for protecting the inner layers from sunlight and damaging chemicals. The second layer is of fiberglass mat having short randomly oriented pieces of fiberglass. The third layer is of woven fiberglass having continuous fiberglass filaments grouped into a cross-hatched weave. A continuous layer of filaments extends parallel to the length of each rail and along each rung.

Tourneau, U.S. Patent No. 2,367,291, discloses a portable and sectional bridge. The spans have a supporting leg connected to the spans by hinges. The legs are positioned by adjustable knee braces. The knee braces are detachable to permit the leg unit to fold against the bottom of the spans so that spans can be stacked one on top of the other for transportation. Spans comprise side beams of box beam construction which, in cross-section, are of trapezoidal form. Box beam joists extend transversely in longitudinally spaced relation and at their ends enter side girders. A transverse reinforcing plate is secured between each joist and top plate. Middle plate flooring sits on and is welded to the joists and extends from end to end in the space between inner girder plates to which it is also welded.

Green, U.S. Patent No. 4,079,476, discloses a fiberglass footbridge having a horizontal floor and a pair of hand rails mounted above the floor and connected to the floor by a solid web of fiberglass. Continuous fiberglass filaments are located at the sides of the floor and at the hand rail to increase resistance to bending. U-shaped supporting members may be mounted around the floor and the web to provide rigidity. A torque box may be mounted

below the floor between supporting members to increase resistance to rotation. The interior side of the webs have an outer surface comprising a layer of resin call gelcoat. The second layer is of fiberglass mat where the fiberglass pieces are short and randomly oriented. The third layer is of woven fiberglass having continuous fiberglass filaments grouped into a cross-hatch weave. The next layer is a continuous layer of unidirectional individual fiberglass filaments extending parallel to the length or longitudinal to the axis of each hand rail. Continuous filament layers are also formed in the floor.

Schafer, U.S. Patent No. 3,591,437, discloses a method of making a plastic building wall fin unit comprising the steps of applying reinforcing fibers to surfaces of a pattern, applying a liquid thermosetting resinous composition to the reinforcing fibers, partially curing the thermosetting resinous composition, applying a lath material to the partially cured thermosetting resinous composition and curing the composition within the pattern.

Meriweather, U.S. Patent No. 4,945,595, discloses a modular ramp assembly constructed of elongated channel-shaped fiberglass modules defining a planar walking surface across the backs of the channel webs. The modules are comprises of fiberglass. Lateral stiffeners are provided extending across the interior of the channel-shape modules between the side flanges for adding strength to the structure. The modules are formed of elongated rectangular elements having a channel-shaped cross-section defined by a horizontal web and a pair of vertical side flanges.

None of these previous efforts, taken either alone or in combination teach or suggest the structure of the present invention, nor do they teach or suggest the benefits and advantages of the present invention.

OBJECTS AND SUMMARY OF THE INVENTION

The practice of the present invention achieves several objectives and advantages. The life span of the described bridge is many times greater than traditional bridges. Polymer materials, used to construct the bridges of this invention, are ideal for bridges. On-going maintenance to the invention is negligible, if any. Polymer materials maintain their strength during incredible flexing. Bridges constructed from this material are subsequently much safer in seismic areas.

Yet another advantage of the invention is that it is manufactured in sections and moved to the site for installation. The sections are transported to the site and then connected. Maximizing bridge completion in the factory minimizes tasks on site. Further, the sections are made so that they are of a size which are easily transportable. In many cases, such as with small county road bridges, the sections may be trucked without any special permits. The structural integrity of a section allows it to be used as its own trailer with only a dolly axle set-up on one end and a hitch configuration on the other.

Yet another advantage of the invention is the great reduction in roadway downtime. Installation of a bridge of the invention should be accomplished in one eight hour day. This provides a great savings to the community by eliminating costly "jump" bridges and the cost of labor. The effects on the environment are also minimized.

The invention also provides the advantage of allowing construction so that the bridge may be placed at any degree of skew. The section of the bridge are easily adjusted to accommodate a stream running at an angle or a river.

It is another advantage of the present invention to provide a bridge that may be employed on a temporary or permanent basis.

It is an additional advantage of the present invention to provide a bridge that can be easily fabricated and installed.

It is even a further object of the invention to provide a bridge that may be manufactured in sections of various lengths to

form bridges of various sizes.

It is still a further object of the present invention to provide a bridge of a non-biodegradable material that is relatively strong, lightweight, flexible and inexpensive.

The invention is a bridge including a plurality of box beams made of fiber and resin formed over a preform. The box beams are connected by fiber and resin and have structural load bearing capacity. The connected box beams form a section and several sections may be connected to form the desired bridge.

In present procedures for wet fiberglass lay-up applications, when a core is incorporated into the lay-up, the core is built into place by piecemeal positioning of discrete core components into the lay-up. The core components are typically made up from sheet stock. Molded core for fiberglass laying has not been generally used in fiberglass lay-ups because styrofoam and polyethylene foams are not compatible with the general purpose resins used to wet the fiberglass mat.

It has been discovered that moldable expandable polyethylene- polystyrene copolymer resins when expanded can be made compatible with polyester and vinyl ester resins i.e., the resins typically used to impregnate and "wet" fiberglass mat for wet lay-ups. This compatibility is achieved by bonding a layer of dry fiberglass mat to the foamed core with a suitable adhesive. The resultant core readily bonds with the fiberglass in a wet lay-up. Since polyethylene-polystyrene copolymer foams are of high strength and relatively low cost, an attractive alternative to prior art core/fiberglass application is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanying drawings in which:

FIG. 1 is a perspective view of an embodiment of the invention;

FIG 2 is a perspective view of a cart rail and impregnating machine used to make the invention;

FIG. 3 is a perspective view of an embodiment of the invention showing a footing and abutment arrangement;

FIG. 4 is a cross-sectional view of the bridge of FIG. 3;

FIG. 5 is a perspective view of a section of the bridge of FIG. 1 showing the construction of an embodiment;

FIG. 6 is a perspective view of a guard rail of the invention;

FIG. 7 is a partial end view of FIG. 1 showing the connection of the bridge sections;

FIG. 8 is a perspective view of an embodiment of the invention showing the sealing of the sections;

FIG. 9 is a perspective view of an embodiment of the invention showing an alternative means for connecting sections of the invention; and

FIG. 10 is a perspective view of a preform of the invention.

FIG. 11 shows an application of the invention in the construction of a small boat.

FIG. 12 shows hull cross-section of the FIG. 11 hull with mold-glass-dry mat-core-dry mat application in that order.

FIG. 13 is the same as FIG. 12 but with Sandwich-Core completed with addition of last layer of glass inside mold (on top of core) .

FIG. 14 shows a typical surfboard construction application utilizing the invention.

FIG. 15 illustrates cost reduction in the core material by using less expensive inner core (such as styrofoam) surrounded by a resin compatible core according to the invention.

FIG. 16 shows a block of styrofoam with all surfaces covered

with bonded polyethylene-polystyrene copolymer sheets.

FIG. 17 and 18 show a block of styrofoam with polyethylene- polystyrene copolymer boards expanded around it and a manufacturing technique.

FIG. 19 shows a way to make hollow segments by dissolving our central styrofoam using a solvent.

FIG. 20 shows a box-beam section out of ARCEL.

DETAILED DESCRIPTION OF THE INVENTION

While this invention may be embodied in many different forms, there are described in detail herein specific preferred embodiments of the invention. This description is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated.

Referring now to FIG. 1, a preferred embodiment of a bridge 10 is shown. The bridge 10 includes a center section 12 and two side sections 14 and 16. In a preferred embodiment, the bridge includes sections which are ten feet by sixty feet. When the sections 12, 14, and 16 are connected a bridge having a span of thirty feet and a pier of sixty feet is constructed. The preferred embodiments is typical of bridges used on secondary roads to overpass roads, streams, rivers, ditches and the like. Bridges of various other dimensions are within the scope of this invention.

In the preferred embodiment, the three sections 12, 14, and 16 are of a size that allows them to be road transportable. As described above, the sections may be ten feet by sixty feet. A truck may be attached to each section by conventional means and it becomes its own trailer. This feature allows for cost and time savings to the user. The size of the sections 12, 14, and 16 also allow for easier manufacturing. Of course, one skilled in the art will recognize that various numbers and sizes of sections may be utilized for various desired applications. Also, this invention allows sections to be connected end to end so that a longer bridge may be constructed. For example, two sixty feet long sections may be connected to obtain a bridge that is one hundred twenty feet in length.

Referring now to FIG. 5, a cut away of a side section 14 is shown. It should be understood that FIG. 5 illustrates section 14 in an inverted position from its use position. As will be described in more detail below, the sections are constructed in this inverted position. As is shown in FIG. 4, each section 12, 14 and 16 is constructed of the same materials and generally in the same manner. However, only one section will be described in

detail. Note that the layers of fiberglass between preforms are described below and shown in FIG. 4 by a line only.

The section 14 includes a layer of wear surface 20. In the preferred embodiment the wear surface 20 is AMOPAVE and is manufactured ^* by AMOCO Oil Corp. of Chicago, Illinois. The wear surface 20 could be a polymer concrete. The wear surface 20 is connected to a layer of fiberglass 22. The weight of this layer of fiberglass 22 is 48/25 ounce fabric/matt per layer and the orientation is unidirectional in the preferred embodiment. However, it should be understood that any suitable weight and orientation may be utilized for a desired application.

The weight and orientation of glass used throughout the invention depends on the width of the bridge to be built, the length, and the strength that is needed for supporting objects which move across it. The fiberglass is impregnated with a plastic resin to provide a fiber reinforced polymer composite as is known in the fiberglass art. The resin is a vinylester resin where a nominal 60% fiber to 40% resin ratio is utilized in the preferred embodiment, for example. Other resins such as ISO/Ortho Polyester may be used and other ratios of fiber to resin are used as appropriate for desired applications.

This layer is fiberglass 22 is connected to a layer of balsa core or extruded thermoplastic compression core 24. The core 24 is placed on the wet glass layer 22 and is vacuum bagged in place. The balsa core 24 is end grain and may be BALTEK core, manufactured by Baltek Corp. of Northvale, New Jersey, for example. This core 24 may also be comprised of a layer of plastic, foam, metal or other desirable core materials. This layer 24 is of varying thickness depending on the specifications of the bridge to be made. For example, bridges of final length of thirty to one hundred twenty feet may use a layer of core 24 having a thickness of three to six inches.

The core layer 24 is connected to a second layer of fiberglass 26 by vinylester resin impregnated in the glass. The second layer of glass 26 is multi-axial glass fabric in the preferred embodiment

and is impregnated with a vinylester resin at a 60/40 ratio, for example.

The second layer of glass 26 is connected to a center preform 28. In the preferred embodiment, a center lane of glass 30 is used to seat the preform 28. The center lane is XM in orientation and is only as wide as the preform 28. The preform 28 may also be coated with resin on the surface that meets the second layer of glass 26 and may then be placed on the layer 26. The preform 28 is made of foam and provides a mold for the layers of glass and resin needed to construct the bridge section. In the preferred embodiment, the preforms are constructed of Arcel 310 foam manufactured by ARCO Chemical. Other materials may be used for the preforms including wood, extruding thermoplastic core or fiberglass. Alternatively, the preforms could be hollow and/or formed of a thermoplastic material. It should be recognized that any number of materials may be utilized for the preforms. As shown in the figures, the preform is elongated and is square in cross- section in the middle. The ends of the form are curved to provide a lip which may be attached to footings for the bridge at installation.

The preforms 28 may be formed integrally as one piece as described above or they may be constructed as shown in FIG. 10. This alternative of preform 28 includes a base 29 and legs 31. This three piece design, i.e. bridge and two legs, allows for easy handling in the manufacturing process. This design also allows for connection of legs 31 to base 29 before construction of the bridge 10 begins or the base 29 and legs 31 may be connected during the construction process. The base 29 of each preform could be placed on the bridge deck and bonded with the layers of fiberglass. The legs 31 may then be added and glassed to ease the fabrication process.

Referring again to FIG. 5, a third layer of glass 32 is connected to preform 28 and is lapped onto layer 26. This layer 32 is 45-45 orientation glass. More than one layer of glass may be used to lap center beam 28. The layers of wetted glass 26, 30 and

32 bond together. In this manner, a "hollow" box beam is formed where the preform acts as a mold for the layers. Several box beams 36, 44, etc. for example are formed by layers of glass and resin by this same means to construct sections 12, 14 and 16. As stated above, in the preferred embodiment, the preforms 28 are made of ARCEL foam. The ARCEL provides additional strength to the box beam. However, it should be noted that the bridge 10 may be manufactured such that the preform does not provide any strength but merely acts as a mold for the layers of glass and resin to form the beam. Again, the preforms may be hollow.

As is seen in FIG. 5, this third layer 32 is of a size and length such that it provides a base for additional preforms on either side of the center preform 28. Preforms 34 and 36 are connected to layer 32 such that the preforms abut preform 28.

Layers of glass 38 and 40 are connected to preforms 34 and 36 and layer of glass 26 of the invention. These layers 38 and 40 are also 45-45 in the preferred embodiment. Preforms 42 and 44 are connected to layers 38 and 40. These preforms 42 and 44 are connected to layers 38 and 40. These preforms 42 and 44 are lapped with layers of glass 46 and 48. A final layer of glass 50 (seen in FIG. 4) is connected to the section 14. This layer 50 provides strength to the section 14. It should be noted that each of the layers of glass and resin described above may include multiple layers of glass of the type described. Several sheets of glass may make up one layer described. The number of layers within a layer will differ depending on the application and design of the bridge.

In this way, each bridge section is made of adjoining box beams of fiberglass. Importantly, the bridge could have a compressional center member, thus functioning like a truss bridge, so that greater span lengths can be obtained with a straight beam bridge. The compressed center member would be positioned transverse to the other longitudinal beams. Unidirectional fibers extending to the transverse member and up the transverse member to produce a truss.

Referring now to FIG. 6, a cut away of a section 14 is shown

illustrating the guard rail 52 of the invention. The guard rail 52 connected to section 16 is constructed in the same manner. The guard rail or side rail 52 includes guard rail spacers 54 and guard rail members 56 which make up the guard rail preform 53. The guard rail preform 53 is made in sections of spacers 54 and members 56 for ease of construction. The members 56 and guard rail spacers 54 may be used for any size bridge as spacers and members are added or removed depending on the length of the bridge 10. The spacers 54 are made of ARCEL foam in the preferred embodiment. The members may be constructed of wood, extruded thermoplastic core, fiberglass, metal or any suitable material. The guard rail spacers 54 and members 56 are connected by means of a glass bonding layer (not shown). The guard rail 52 is connected to preform 44. The members 56 are received by preform 44 and are held in slots 58. The guard rail is glassed to the preform 44. The slots 58 may be molded into the preform 44 or cut in as desired. Alternatively, the guard rail could be a Jersey style guard rail of a thermoplastic.

The bridge 10 is manufactured in a manner which produces multiple box beams of fiber reinforced polymer. The box beams are connected into sections and form a strong, durable bridge when the sections are joined together. As discussed above, in the preferred embodiment the bridge is comprised of three sections. The sections are manufactured by the same process except that any center section or sections such as 12 do not include a guard rail.

An impregnator machine 60 is used to manufacture the bridge 10. The impregnator 60, shown in FIG. 2, includes one or more rollers 64 which hold the materials to be impregnated. The impregnator 60 also includes means 66 for impregnating the glass with resin so that wetted glass may be applied for manufacture. Impregnators are known to those skilled in the art. In the preferred embodiment, the impregnator 60 is a Venus Four roll fully articulated sixty inch impregnator. As seen in FIG. 2, the impregnator 60 includes a gantry system 62 to suspend the material over a work surface. The impregnator moves on wheels 63 by means

of the gantry system 62 to allow for positioning.

The manufacturing of a bridge 10 also requires use of an apparatus to support the sections 12, 14, 16 during their construction for application of wetting glass and other components. A mold cart 70 is used in the preferred embodiment. The mold cart 70 includes deck 72 connected to a frame 74 and is supported by wheels 76. A track or rail 78 is used in conjunction with the mold cart 70 such that the wheels 76 ride on the rail. In this manner, the mold cart 70 may move relative to the impregnator 60. Also, the impregnator 60 may move relative to the mold cart 70. However, it is preferable in the manufacturing process for the impregnator 60 to remain stationary and to move the cart 70. The mold cart 70 is made of steel in the preferred embodiment and is ten feet wide and sixty feet long. It should be understood that any suitable material should be used and the dimensions of the cart may be varied based on the dimensions of the bridge to be manufactured.

In manufacture of a section, the mold cart 70 is prepared to accept the first layer of material. The mold cart 70 includes a release surface of polyethylene or polypropylene so that the bridge 10 will not adhere to the cart during the manufacturing process and an easy release is achieved upon completion of the bridge 10. As discussed above, each section 12, 14, 16 is built in an inverted position from the use position. After the mold cart 70 is prepared, the layer of wear surface link or AMOPAVE 20 is applied to the cart. Referring now to FIG. 4 and 5, the next layer of material is then applied to the mold cart. The AMOPAVE surface is covered with a heavyweight multi-axial glass stitch bonded fabric and a vinyl ester resin 22 at a nominal 60/40 resin ratio. In the preferred embodiment, two passes are made so that two layers of the impregnated glass are rolled out onto the cart 70. These layers of fiberglass 22 are 0-90 in orientation and a weight range of 48 ounce to 120 ounce may be used on a bridge with a pier of sixty feet and a span of thirty feet. This fiberglass 22 is then rolled out to remove any air bubbles so that a strong bond may form between the several layers of materials used in each section.

Rolling out the fiberglass is a process that is well known in the art and will not be described further.

Next, the layer of core 24 is inserted into the wet glass 22 and vacuum bagged in place. The vacuum bagging process is well known to those skilled in the art and will not be described further. The residual vacuum film (not shown) from the vacuum bagging process is then stripped from the core layer 24.

The second layer of glass 26 is then applied with the impregnator 70 to the exposed surface of the core 24. The glass 26 is multi-axial with an orientation of 0-90 and the vinyl ester resin is used in a 60/40 ratio. After the layer has been applied, it is rolled out to remove air bubbles.

A center lane of impregnated fiberglass 30 is laid on second layer 26 to seat the first beam preform 28. This layer of glass is XM in orientation and is impregnated with resin at a 60/40 ratio. The first of five beam preforms 28 is lowered onto the center layer of glass 30 on the mold cart 70. In the preferred embodiment, the center preform 28 is lowered onto the layer 30 which is applied in a centered position on the mold cart 70. The preform 28 is then coated with a layer of wet resin (not shown) to provide a suitable surface for bonding. The preform 28 is pre-coated or wet so that a good bond between the preform and the impregnated fiberglass is insured. All surfaces that are not "wet" are pre-coated before fiberglass is applied.

The third layer of glass 32 is applied to preform 28 and a desired portion of second layer 26. This layer of glass 32 is multi-axial and has an orientation of 45-45. The glass 32 covers the visible portions of preform 28 as well as the portions of layer 26 that form a base for preforms 34 and 36. The glass 32 covers the second layer 26. It should be understood that this layer o _f glass may cover more or less of layer 26 depending on the desired bridge.

In turn, each of the adjacent preforms 34 and 36 are lowered onto the layer 32. The preforms 34 and 36 abut preform 28. A next layer of glass 38 is applied to preform 34. The layer 38 covers

preform 34 and the second layer of glass 26 which is exposed adjacent to preform 34 to provide a base for the next preform. The glass 38 is impregnated with vinyl ester resin and is multi-axial with an orientation of 45-45. The layer of glass 38 may overlap onto layer 32 as shown in FIG. 5 or may meet the edge of preform 28. Another layer of glass 40 is applied to preform 36 in the same manner. The glass 40 is of the same type as that applied to preform 34 and covers the second layer 26 exposed adjacent to preform 36 to provide a base for the next preform.

Preform 42 is placed on the mold cart 70 on layer 38 and adjacent to preform 34. Another lay of glass 46 is applied to preform 42. The glass 46 is of the same type as that of layer 40. The preform 42 is molded with a groove 80. As shown in FIG. 4, the center section 12 includes tongues 82 and 84 and sections 14 and 16 include grooves 80. As will be described below, the tongue 82, 84 and groove 80 are utilized to connect section 12, 14, and 16. In manufacture, the glass used to cover these preforms is applied with a mold (not shown) . The glass layer 46 is applied to preform 42 with a mold.

Preform 44 is placed on the mold cart 70 on layer 40 and adjacent to preform 36. Another layer of glass 48 is applied to preform 44. The glass 48 is of the same type as that of layer 40.

The guard rail 52 may now be attached to the preform 44. The guard rail 52 is prepared separately from the sections 12, 14, and 16. The guard rail is prepared so that when it is attached to a section of the bridge the surfaces of both are wet to ensure a good bond. A guard rail mold (not shown) is used to obtain the desired shape of rail. Different rails may be used for different applications to provide appropriate decorative shapes to the rails. The desired mold is waxed and a layer of gelcoat is then applied. A colored neo-pental glycol gelcoat is used, although it should be understood that any appropriate coating may be used for the intended purpose. The mold is then glassed with a guard mold layer 88 of multi-axial stitch bonded glass fabric and vinylester resin. The impregnated glass is rolled out to remove air bubbles. A guard

rail layer of balsa core 90 is set into the wet glass 88 and is vacuum bagged into place. The guard rail balsa core is an end grain baltex core. The vacuum layer is stripped away and a glass guard rail layer of glass 92 is applied to the outer guard rail core 90. A glass of the same type as layer 88 is utilized. This layer is rolled out to removed air bubbles. The guard rail preform 53 is now bonded into the wet glass guard rail layer 92. In this manner, guard rail 52 is formed.

The guard rail 52 is connected to the preform 44 and the exposed layer of glass 22. The guard rail 52 is tipped up into place and clamped to the section. The wet layers of impregnated glass 48 and 22 bond the rail 52 to the section 14.

A last layer of glass 94 is then applied to the section. The surface of the section and the guard rail are covered in their entirety by the final layer 94. This layer 94 is unidirectional glass and like the other layers may include several layers of impregnated fabric. This layer 94 provides strength and rigidity to the bridge by further bonding the box beams formed by the other layers of impregnated glass. In this manner, the bridge tension member is formed.

All the layers of fiber glass and resin are applied within a sufficient time period so that co-curing of all the layers of resin and glass is achieved. This co-curing provides a strong bond to form the beams and bonds the beams together. Thus, a bridge having the desired load bearing capacity is formed.

Each finished section is covered with a coating of neo-pental glycol gel coat. This provides a seal for the sections. It should be understood that other appropriate coating may be used.

The sections are now ready to be transported and assembled. Referring now to FIG. 3, a bridge 10 is shown in dirt abutments 100. At the bridge site, footings 101 are poured below frost level and allowed to cure. After the footings cure, the center section 12 is placed in its proper position. The sections 14 and 16 are then placed on the appropriate footings but with a two to three foot gap between the sections 12, 14, and 16. Wet out glass fabric

102 is then draped on the tongues 82 and 84 of section 12, shown in FIG. 7. Sections 14 and 16 are then forced toward the tongues 82 and 84 to close the gap between the sections. The tongues 82 and 84 and grooves 80 are properly mated and the wet out glass 102 provide a bond for the sections.

As is seen in FIG. 7 and 8, the seams between the sections are taped with a tape 104 to eliminate air leaks. A vacuum fitting 106 is connected to each seam and an air compressor (not shown) is used to provide a vacuum source to vacuum bond all the sections 12, 14 and 16 together. After final curing, the bridge 10 may be wear surface paved and final stone fill and site work may be completed.

Referring now to FIG. 9, a bridge 10 is shown. The bridge 10 is comprised of three sections 12, 14, and 16 but has not been permanently sealed together as described above. The bridge sections are connected by means of a connector 110 and fasteners 112. It may be desirable to temporarily connect the sections of the bridge to provide a temporary bypass during construction. Therefore, means are provided to connect the sections and allow for disconnect when appropriate. It should be understood that any appropriate means for temporary connection may be utilized in the invention.

The core fiberglass structures of this invention are readily adaptable not only to all fiber reinforced plastic (FRP) applications such as boat hulls, surf boards, architectural panels and the like but to unusual applications such as support beams for truck trailers and bridges. Further, this invention may be used in connection with other thermoplastic matrixes, i.e. fiberglass can be attached by this invention to thermoplastic matrixes.

The most preferred expandable, moldable polyethylene- polystyrene copolymer boards for use in this invention are the ARCEL resins available from ARCO Chemical Company, a Division of Atlantic Richfield Company with offices at 3801 West Chester Pike, Newtown Square, Pennsylvania 19073. These moldable foams are closed cell expandable resin boards which can be molded in low pressure steam chest equipment. These resins can be molded in a

wide range of densities to produce intricate shapes and high strength and toughness. Molding can be accomplished using conventional equipment already used to produce expandable polystyrene resins and the expanded articles can be subjected to conventional techniques such as die-cutting, routing, saw cutting and hot wire cutting, as necessary.

In accordance with this invention, once a core has been expanded to a predetermined configuration, for example the core 210 shown in FIG. 11, such as might be used in the construction of a boat hull or other application, it is then covered (at least those surfaces which are to contact wet fiberglass) with a dry layer of fiberglass mat. The mat is bonded to the foam by means of an adhesive. A preferred adhesive is of the type described as single component, 100% solids liquid polyurethane adhesive which cross¬ links to form a thermoset polymer after application. Such an adhesive is available as Swift 22005 from Swift Adhesives, Division of Reichold Chemicals, Inc., Downers Grove, Illinois. A roller coater grade is available as Swifts 22006. Other adhesives, such as hot melt polyurethane are also suitable. 3M Jet-Melt™ adhesives are an example of this type.

After the core is completed by bonding the dry fiberglass mat 211 to those surfaces of the expanded copolymer to be constructed as shown in FIG. 12, it may be incorporated into a wet lay-up for example as shown in FIG. 13. In this lay-up, a female mold 212 has been used for the initial lay-up of wet fiberglass mat 214. Following the lay-up in mold, core 210 may be dropped into mold 212 over the wet fiberglass lay-up 214. Bonding between the wet fiberglass 214 in the mold 212 and the dry fiberglass 211 on core 210 then occurs.

If a typical sandwich construction is desired i.e., FRP/Core/FRP, then another wet lay-up of fiberglass 215 is placed over the core as shown in FIG. 13. It can be seen that the invention makes the use of a "net shaped" core which may be molded to a desired shape. In the boat, the entire core does not have to be covered with the dry mat. It is most important that the outside

area, which is subject to stresses, is covered to a strong bond between the core and the wet lay-up fiberglass. It may, however, be desirable to bond dry fiberglass mat to all surfaces on which there is to be west lay-up.

In the embodiment of the invention as shown in FIGS. 11-13, the core is premade in a mold of its own to a shape which fits a female mold used for the wet lay-up. After the core is place in the female mold, wet fiberglass may then be placed over the core.

Another embodiment is shown in FIG. 14, in which two female molds 220 and 222 having the shape of a surf board for example are used for wet lay-up. A net shape core 224 of foam coated with dry mat as before is placed in mold 219. Both mold halves contain wet fiberglass lay-up 226, 228. Mold 220 is closed down on top of mold 222 in the manner in which a suitcase is closed. This is shown in FIG. 15. Molds 220 and 222 are shown closed with the fiberglass lay-up 226 and 228 in each and the dry mat coated foam core 224 in the center. This is of course schematic.

It is also possible to make hybrid cores according to this invention. For example, to lower cost, a core may be formed which consists of polyester-polystyrene copolymer on its wet lay-up contact surfaces (usually the entire outer surface) and the interior of the core may be formed of a less costly material such as styrofoam.

Such an arrangement is shown in FIG. 16 in which a block of styrofoam 230 is covered with sheets of polyester-polystyrene copolymer foam 232 by adhesive bonding.

Another arrangement is shown in FIGS. 17 and 18 in which a block of styrofoam 236 is suspended in a mold and the polyester- polystyrene copolymer boards are expanded 238 around it. The resultant structure is shown in FIG. 17. For example, core 236 might be suspended on a wire 235 as shown in FIG. 18 such that foam

238 may be formed around the core in mold 237.

If for some reason such as in aircraft construction of the like, it is desired to provide hollow foamed cores, a molded core

239 according to the invention with a styrofoam center 240 may be

hollowed out by dissolving the styrofoam away with a suitable solvent such as paint thinner as schematically indicated in FIG. 19. Such solvent is poured in via entrance hole 250 and is drained out exit hole 251.

To make strong support beams of varying lengths, an elongated foam beam covered with a dry layer of mats is prepared much as described above. Wet fiberglass is then overlaid on all four sides of the beam. Such a beam is shown in FIG. 20 in which the core 240 is covered with dry material 241 and then with a lay-up of wet fiberglass 242 to form the long beam 244.

In the various descriptions above, no reference has been made to a gelcoat outer layer, the use of which is known in the art. It is to be understood that gelcoat may be incorporated into the various embodiments.

The above examples and disclosure are intended to be illustrative and not exhaustive. These examples and description will suggest many variation and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the attached claims.

Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims attached hereto.