High strength, light weight shoring panel and method of preparing same

A structural composite panel which is adapted to be used as a shoring panel in a generally vertical plane so as to protect against the collapse of excavated walls and which comprises:

• (a) a first substantially flat facing layer for providing an interface between an excavation wall and an underground worker;
• (b) a second facing layer spaced from said first facing layer and extending substantially parallel thereto;
• (c) four end sections integrally formed along the entire perimeter of the panel and connecting said first and second facing layers along the entire periphery thereof;
• and
• (d) core means disposed between said first and second facing layers, said core means having generally flat first and second surfaces lying substantially parallel to said first and second facing layers and having substantially flat end sections disposed generally perpendicular to said first and second facing layers, said core means being comprised of cellular material having a high strength to weight ratio and having a length and width substantially greater than the thickness thereof;
• wherein said first and second facing layers comprise at least four layers of fiber reinforced hardenable resin material, wherein a first of said layers of fiber reinforced hardenable resin material is disposed adjacent to said first surface and is comprised of fiber matting, wherein a second of said layers of fiber reinforced hardenable resin material is disposed adjacent to said core means and is comprised of fiber matting, and wherein the remainder of said at least four layers of fiber reinforced hardenable resin material are adjacent to each other, are disposed between said first and second layers of fiber reinforced hardenable resin material and are comprised of fiber roving;
• wherein said hardenable resin material is selected from the group consisting of epoxy, phenolic, vinylester, polyester, polyamide, polyamide, polyurethane and polysulphone resin material;
• wherein said fiber matting and said fiber roving fiber reinforcing material are disposed in said resin material such that the fibers thereof lie in a generally planar array which is substantially parallel to said first and second facing layers;
• wherein said panel weighs less than about 6 pounds per square foot;
• and wherein said panel, when supported over its entire height, on each vertical extending end, by no more than 5 inches, is able to withstand an extended load in Type C soils (OSHA, CFR 1926) of at least 592 pounds per square foot with a minimum safety factor of 3:1.