Stock material or miscellaneous articles – Structurally defined web or sheet – Including fastener for attaching to external surface
Reexamination Certificate
1998-10-20
2001-09-18
Copenheaver, Blaine (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including fastener for attaching to external surface
C428S119000, C428S317900, C428S319900, C442S373000
Reexamination Certificate
active
06291049
ABSTRACT:
FIELD OF INVENTION
This invention relates to a truss reinforced foam core and to such a foam core which can be incorporated as a part of a sandwich structure, the manufacture of which does not require the use of an autoclave
BACKGROUND OF INVENTION
In U.S. Pat. Nos. 5,624,622 and 5,741,574 incorporated herein by this reference, there are disclosed truss reinforced foam core sandwich structures wherein a plurality of pins are disposed in a foam core and the extending ends of the pins are then driven into composite face sheets on each side of the foam core. See also U.S. Pat. No. 5,736,222 also incorporated herein by this reference.
One potential drawback with these structures is that an autoclave must generally be used to obtain the pressure required to drive the pin ends into the face sheets.
An autoclave adds significantly to the cost of manufacturing such sandwich structures and for large structures the use of an auto-lave may be impractical.
SUMMARY OF INVENTION: I
It is therefore an object of this invention to provide a truss reinforced foam core sandwich structure and method of making such a sandwich structure that does not require the use of an autoclave.
It is a further object of this invention to provide such a sandwich structure and method which is extremely versatile.
It is a further object of this invention to provide such a sandwich structure which is significantly less expensive to manufacture than prior art sandwich structures.
It is a further object of this invention to provide such a sandwich structure and method which prevents delamination of the face sheet; from the core material.
It is a further object of this invention to provide such a sandwich structure and method which results in a sandwich structure having improved shear strength, compressive strength, and fatigue strength.
It is a further object of this invention to provide an improved truss reinforced foam core body which may be used in the manufacture of sandwich structures.
This invention results from the realization that many of the beneficial characteristics of a truss reinforced foam core sandwich structures can be obtained by bending the ends of pins extending from the core over the surfaces of the core and then assembling the face sheets on the core and over the bent over pin ends thus eliminating the expense and impracticability of using an autoclave to drive the pin ends through the face sheets of the sandwich structure.
The pins secure the face sheets to the foam core since the pins extend from one face sheet to the other and their bent over ends become part of the face sheets. In addition, the pins reinforce the foam core and greatly improve the shear, compressive, and fatigue strengths of the sandwich structure.
This invention features a sandwich structure comprising a core having opposing top and bottom surfaces; a plurality of discrete pins disposed through the core and extending beyond the top and bottom surfaces of the core; a face sheet on the top core surface; and a face sheet on the bottom core surface, the ends of each pin bent over and lying between the respective core surfaces and the face sheets.
The core is typically made of foam. Each pin may include strands of fiber and the strands of fiber are separated from each other at the extending bent over ends of each pin. The pins may also be wires.
Each face sheet preferably includes an array of fibers in a resin matrix. The array of fibers may form a fabric. Alternatively, each face sheet is made of metal.
The pins are typically disposed at an angle in the core forming a truss structure therein. Each pin may be angled differently from each adjacent pin. The bent over ends of the pins may form a repeating pattern of sets of pin ends along the top and bottom surface of the core. Each pin in a set of pin ends in the top surface extends to a different set of pin ends in the bottom surface. And, each pin end in a set of pin ends is bent in a different direction.
This invention also features an improved core without any face sheets to be incorporated into a sandwich structure with face sheets. The improved core comprises a core body; a top and bottom surface; and a plurality of discrete pins inserted through the core, the ends of each pin extending from the top and bottom surfaces of the core and bent over and lying along the respective top and bottom surfaces of the core. The core body is typically foam but may be any cellular material. Each pin may include strands of fiber and the strands of fiber are separated from each other and splayed out at the bent over ends of each pin. The pins are preferably disposed at an angle in the core forming a truss structure therein and each pin is angled differently from each adjacent pin. The bent over ends of the pins preferably form a repeating pattern of sets of pin ends along the top and bottom surface of the core and each pin in a set of pin ends in the top surface of the core extends to a different set of pin end in the bottom surface of the core. Also, each pin end in a set of pin ends is bent in a different direction.
In another embodiment, the sandwich structure of this invention includes a core having top and bottom surfaces; a top face sheet material layer on the top core surface; a bottom face sheet material layer on the bottom core surface; and a plurality of pins disposed both through the core and the face sheet material layers and extending beyond the face sheet material layers. The extending ends of each pin are bent over and lie along the exterior of the respective face sheet material layers.
The face sheet material could be a dry fabric (e.g. fiberglass before it is impregnated with resin) or a prepreg material. The pins are usually discrete and do not join with adjacent pins.
This invention also features a method of manufacturing a sandwich structure, the method comprising disposing a plurality of pins through a core such that the ends of the pins extend from the core; bending the extending ends of the pins over to lie on the core; and assembling face sheets on the core and over the bent over pins.
The pins may include strands of fiber coated with a resin and the step of bending includes subjecting the pins to heat and pressure by placing the core/pin combination in a hot press. The step of assembling the face sheets includes laying a prepreg layer on the core over the bent pin ends and curing the prepreg layer. Alternatively, the step of assembling the face sheets includes laying a dry fabric layer on the core over the bent pin ends, impregnating the dry fabric layer with resin, and curing the resin.
Disposing the pins includes inserting the pins at an angle in the core forming a truss structure therein. Inserting the pins may include orienting each pin at an angle different than the angle of each adjacent pin. Disposing the pins also typically includes forming a repeating pattern of pin end sets, each pin, in each set of pin ends on one surface of the core extending to a different set of pin ends on the other surface of the core. The pin ends of each set of pin ends are bent in a different direction. This invention also features the product made by this method.
The method of manufacturing an improved core for a sandwich structure in accordance with this invention includes inserting a plurality of pins through a core such that the ends of the pins extend from the top and bottom surfaces of the core; and bending the extending pin ends over to lie along top and bottom surfaces of the core.
The step of inserting the pins includes disposing the pins at an angle in the core forming a truss structure therein. The angle of each pin is preferably different from the angle from each adjacent pin. The method may include forming a repeating pattern of sets of pin ends, each pin end in each set of pin ends on one surface of the core extending to a different set of pin ends on the other surface of the core. The pin ends of each set of pin ends are preferably bent in a different direction. This invention also features the product made by this method.
In another embodiment, a plurality of pins a
Blaney Eric
Kunkel Edward
Magee Constance
Rich David
Aztex, Inc.
Copenheaver Blaine
Iandiorio & Teska
Paulraj Christopher
LandOfFree
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