Stock material or miscellaneous articles – Pile or nap type surface or component – With coating – impregnation – or bond
Patent
1995-06-02
1998-02-24
Lee, Helen
Stock material or miscellaneous articles
Pile or nap type surface or component
With coating, impregnation, or bond
428114, 4282924, 4282937, B32B 508, B32B 516
Patent
active
057210365
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention pertains to reinforcement of structural wood, such as beams, columns and trusses. More particularly, the present invention pertains to the use of unidirectional fibers as a reinforcement in structural wood members to improve the tensile or compressive loading of the wood member.
BACKGROUND ART
To remain competitive, wood product engineers have had to adopt innovative designs in combination with alternate materials to enhance the structural limits and cost effectiveness of engineered wood products. Examples of engineered wood products include glued laminated wood beams, laminated wood columns, wood I-beams, and wood trusses. The prior art is replete with examples of these engineered wood products.
O'Brien, U.S. Pat. No. 5,026,593 discloses the use of a thin flat aluminum strip to reinforce a laminated beam. O'Brien teaches that the aluminum strip must be continuous across the width and length of the beam and that the reinforcing strip may be adhesively fixed to the lowermost lamina to improve tensile strength, or to the uppermost lamina to improve strength in compression of the beam. Thus, while O'Brien teaches the engineering principal of locating a reinforcement strip in a wood laminated beam to improve the tensile strength (or strength in compression) of the beam and thus to improve the overall load carrying capacity of the beam, O'Brien only teaches the use of an aluminum reinforcing strip. And although O'Brien states that the reinforcing strip may be any "high tensile strength" material, O'Brien does not teach nor suggest means for optimizing the reinforcing strip nor of solving problems associated with the use Of reinforcing strips other than aluminum.
At the 1988 International Conference on Timber Engineering a paper was presented entitled "Reinforced Glued-Laminated Wood Beams" by Mr. Dan A. Tingley (hereinafter "Tingley Paper") that disclosed the use of reinforced plastics (RP) in glue laminated wood beams (glulams). The Tingley paper disclosed test results of glulams having "KEVLAR" reinforced plastic panel(s) located at high stress areas. The results indicated a 19% improvement in ultimate load-to-failure of beams with "KEVLAR" reinforcement as opposed to nonreinforced beams. Although not disclosing why longitudinal alignment was desirable or how it was achieved, the paper states that the manufacturers were able to achieve one hundred percent longitudinal alignment of fibers. The paper also disclosed that the reinforcing panel was sanded on two sides and further stated that the sanded surfaces of the "KEVLAR" reinforced panel was found to be important. However, the paper does not disclose why the sanding was important nor a suggestion that the sanding process exposed or abraded the "KEVLAR." fibers. The Tingley paper also teaches that there are economic advantages to shortening the length of the RP relative to the length of the glulam beam without significant reduction of reinforcement benefit in beam strength. The Tingley paper does not disclose any process for fabricating RP reinforcement panels, nor benefits associated with curing the panels while the fibers are in tension to reduce initial strain. Nor does the paper disclose the benefits of exposing some of the outermost fibers in order to "hair up" the RP to produce a surface that facilitates the use of commercial grade adhesives such as resorcinol. On the contrary, the paper teaches away from resorcinol adhesives by teaching the use of epoxies to adhere the RP to the surrounding wood laminas even though the less expensive commercial adhesive, resorcinol, was used between the other layers of wood laminae.
Another area of related art is the fabrication process of pultrusion. Pultrusion is defined as a continuous manufacturing process for producing lengths of fiber reinforced plastic parts. Pultrusion involves pulling flexible reinforcing fibers through a liquid resin bath and then through a heated die where the RP is shaped and the resin is cured. Pultrusion is known for its ability to fabricate a continuous
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