Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Patent
1993-10-08
1995-11-07
Withers, James D.
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
114 90, 114 91, 114 93, 114103, 343872, 428 361, 428 363, 428113, 428257, 428258, 428259, 428284, 428294, 428302, 428408, 428902, B32B 506, B29D 2200, B63B 1500
Patent
active
RE0350818
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a composite structural member having a high bending strength. More particularly, the invention is directed to a composite structural member having a unique ply geometry and construction which contributes to a high bending strength.
A number of composite materials are well known in the art and have been used for applications requiring lightweight and high strength. Such materials are constructed of one or more plies, or layers, at least some which have a fiber component embedded in a polymer matrix. The geometry of the fiber component within each layer contributes to the strength and other properties of the ultimate structure.
Many composite materials are susceptible to structural failure when subjected to excessive bending, compressive or torsional strains. It would be advantageous to provide a lightweight structure able to withstand greater forces.
Accordingly, an object of the present invention is to provide a composite structure having a ply geometry which contributes to improved strength, particularly bending strength. Another object is to provide a lightweight elongate composite structural member having high strength. It is also an object to provide a convenient and efficient method of manufacturing such composite structural members. Other objects of the invention will be apparent to those of ordinary skill in the art upon reading the following disclosure.
SUMMARY OF THE INVENTION
The present invention relates to a composite structural member having improved strength. The composite member is generally elongate and may have various cross-sectional tubular, i.e. hollow, profiles such as circular, rectangular, square and the like. The composite is constructed of a number of plies, each of which has a fiber component disposed within a polymer matrix. The ply geometry of a composite structure that has at least three plies is such that inner and outer plies have continuous, circumferential fibers which are oriented at an angle of between .+-.30.degree. to .+-.90.degree. relative to the longitudinal axis of the composite structural member. There is at least one of each such inner and outer circumferential plies. The circumferential fibers provide crush strength, and reinforce axially-extending fibers against buckling failure. The resistance to crush strength is in part a function of the cosine.sup.2 or sine.sup.2 of the foregoing angle between the circumferential fiber orientation and the longitudinal axis of the member.
The composite structure also has at least one intermediate ply having first axially extending fibers in circumferentially spaced sets with circumferential gaps between each set of the first fibers. A set of second axially extending fibers is disposed between each set of first axially extending fibers. These second axial fibers are interwoven with helically oriented braiding fibers, which are disposed at an angle of between .+-.5.degree. and .+-.60.degree. relative to the longitudinal axis of the composite member. Both the first and second axial fibers are oriented substantially parallel, i.e. at an angle of approximately 0.degree. to the longitudinal axis of the member. Preferably, each set of first and second axial fibers comprises two adjacent fibers. The first and second sets of axial fibers cooperate to render the wall thickness throughout the composite substantially uniform.
The circumferential fibers and the braiding fibers may be a variety of fiber materials, including aramid, carbon, graphite and glass, with a modulus greater than ten million psi. The axial fibers may be of fiber materials such as carbon, graphite, ceramic, boron and glass, and with a modulus of at least twelve million psi to withstand bending stresses. The matrix component of the composite, i.e. that portion of the structure excluding the fibers, typically has as its major component a polymer resin and/or ceramic able to penetrate and bond well to the fiber component and able to form secure bonds between the plies. The matrix material, which is selected to be
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International Search Report for Application PCT/US90/03439.
Fiberspar, Inc.
Withers James D.
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