Stock material or miscellaneous articles – Hollow or container type article – Shrinkable or shrunk
Reexamination Certificate
1999-03-15
2001-05-22
Cain, Edward J. (Department: 1714)
Stock material or miscellaneous articles
Hollow or container type article
Shrinkable or shrunk
C428S035100, C428S035700, C428S036300, C428S036900, C428S297400, C428S913000
Reexamination Certificate
active
06235357
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to a reinforced structural composite consisting of fibers in a polymer matrix; and, in particular, to a responsive, externally-activated two phase material consisting of pre-stressed continuous fibers, restrained and controlled by a discontinuous fiber reinforced polymer matrix, wherein both matrix and matrix reinforcing relax at and above a specified temperature.
For the purpose of the current invention the term “fiber” is defined to mean a slender and greatly elongated shape from natural and synthetic material which has tensile strength and comprises fiber, thread, fiber bundles, tow, and filament bundles.
b) Description of the Prior Art
Since the advent of high-strength fibers and their incorporation into polymer composites, the focus within the prior art has been on the structural ability of composites to resist external forces. A multitude of fibers, fiber arrangements, and polymer matrix compositions has been utilized for structural composites. Structural composites are inert materials resisting loads. The present invention concerns a polymer composite that generates force as well as resists force.
In the polymer composite prior art Bettinger, U.S. Pat. No. 5,552,197, discloses dynamic polymer composites which generate delayed dimensional change and force due to pre-stressed fibers constrained and controlled within and by a responsive polymer matrix whereby the response is self-activated time-dependent. Bettinger is limited by the strength of a non-reinforced matrix and the transverse strength of a matrix reinforced by longitudinal fibers. Bettinger is a cylindrical mechanism not a material. The compressive force of Bettinger is limited.
SUMMARY OF THE INVENTION
This two-phase composite comprises high-modulus continuous pre-stressed fibers selected to maintain tension over a temperature range both below and above an activation temperature. The continuous fibers are within a polymer matrix reinforced with short, discontinuous fibers. The reinforced matrix is selected to compressively restrain the pre-stressed fibers below an activation temperature. Above this activation temperature the selected polymer matrix ceases restraint and deforms to provide an external force release and dimensional change. The reinforced polymer matrix is the responsive component and acts to restrain, balance, and control stress that was induced in the fibers during the process for preparing the composite material. Once this polymer matrix is prepared the discontinuous short length fibers impart desirable structural characteristics: high creep resistance, high strength, and high impact resistance.
1. Objects of the Invention
A general object of this invention is to provide a dynamic polymer composite material that is highly resistant to creep particularly during storage and shipping prior to activation.
Another general object of this invention is to provide a responsive composite material that possesses high strength in service.
Another general object of this invention is to provide a responsive composite material that is impact resistant in service.
Another general object of this invention is to develop a structural, dynamic, polymer composite material to be utilized for connecting composite structures.
Another general object of this invention is to provide a material that may be incorporated into actuators for deployment, retraction, contraction, and expansion mechanisms replacing complex and expensive electromechanical actuators.
2. Features of the Invention
In keeping with these objects and others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in the discontinuous fiber reinforced and responsive polymer matrix which affords the composite with the attributes of high creep resistance, high structural strength, and high impact resistance.
Another feature of this invention is that the key to the design versatility of this new structural composite is the selection of the discontinuous fibers that provide compressive reinforcement within the polymer matrix and yet yield with the polymer matrix. The polymer matrix controls the release of the continuous fiber tension. The composite response is on-demand externally-activated based on exposure to independent stimuli such as heat, light, or chemicals.
Another feature of this invention is the ease of activation without the need for solvents or tools beyond a heat source.
In order to overcome the previously mentioned deficiencies and problems in the prior art, this invention discloses a two phase dynamic polymer composite comprising high-modulus, continuous, pre-stressed fibers within a polymer matrix possessing a Tg below that of the continuous fibers, and compressively reinforced by discontinuous short fibers with a Tg below that of the polymer matrix, such that when the composite temperature is greater than the Tg of the matrix, this compressive reinforcement ceases. Simultaneous to this cessation the tension fibers force the deformation of the polymer matrix when activated by heating above the Tg of the polymer matrix. By careful selection of the discontinuous fibers to be entrained within the polymer matrix the structural attributes of creep resistance, structural strength, and impact resistance can be controlled.
A two phase polymer composite comprises:
a) high-modulus, continuous, pre-stressed fibers selected
to maintain tension below and above an activation temperature, within
b) a polymer matrix selected
to compressively restrain said pre-stressed fibers below, and
to cease said restraint and deform above said activation temperature to provide an external force release and dimensional change, reinforced by
c) discontinuous and short fibers selected
to maintain a high modulus below, and
to relinquish modulus above said activation temperature.
It will be recognized by one of ordinary skill in the art that the continuous fibers used in the polymer matrix may be knit, braided, sewn and woven. Discontinuous fibers are generally featured in sheet molding and injection molding processes. It is understood by one of ordinary skill in the art that certain embodiments of the present invention may be incorporated into devices for connectors, structural assembly, and mechanism actuation. These and other modifications and applications of the present invention will become apparent to those skilled in the art in light of the following description of embodiments in this invention. Drawing Description:
REFERENCES:
patent: 5188260 (1993-02-01), Bettinger
patent: 5552197 (1996-09-01), Bettinger
patent: 5752926 (1998-05-01), Larson et al.
Bettinger David S.
Stoll Frederick
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