(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2003/0236588A1
`Jang et al.
`(43) Pub. Date:
`Dec. 25, 2003
`
`US 2003O236588A1
`
`(54)
`
`NANOTUBE FIBER REINFORCED
`COMPOSITE MATERIALS AND METHOD
`OF PRODUCING FIBER REINFORCED
`COMPOSITES
`(76) Inventors: Bor Z. Jang, Fargo, ND (US); Jun H.
`Liu, North Huntingdon, PA (US);
`Shizhu Chen, Chang-Sha (CN);
`Zhimin M. Li, Auburn (AL); Hassan
`Mahfuz, Auburn, AL (US); Ashfaq
`Adnan, Tuskegee, AL (US)
`Correspondence Address:
`GARDNER GROFF, P.C.
`PAPER MILL VILLAGE, BUILDING 23
`600 VILLAGE TRACE
`SUTE 300
`MARIETTA, GA 30067 (US)
`Appl. No.:
`10/389.261
`
`Filed:
`
`Mar. 14, 2003
`Related U.S. Application Data
`(60) Provisional application No. 60/364,344, filed on Mar.
`14, 2002. Provisional application No. 60/366,097,
`filed on Mar. 20, 2002.
`
`(21)
`(22)
`
`Publication Classification
`
`(51) Int. Cl." ..................................................... G06F 19/00
`(52) U.S. Cl. ......................................... 700/119, 264/176.1
`
`(57)
`
`ABSTRACT
`
`A composite composition and a method of making Such a
`composite that is composed of a matrix material and dis
`persed reinforcement nanotubes that are Substantially
`aligned along at least one specified direction or axis. Also a
`method for making a continuous fiber-reinforced composite
`object by combining a reinforcement fiber tow with a
`Solidifying matrix material to form a pre-impregnated tow or
`towpreg, providing a dispensing head capable of dispensing
`the towpreg onto a base member positioned a distance from
`this head with the head and base member being driven by
`motion devices electronically connected to a motion con
`troller regulated by a computer, and operating and moving
`the head relative to the base member to dispense multiple
`layers of towpreg in accordance with a CAD-generated
`deposition path along which the dispensing head can be
`allowed to trace out individual layers by following a Selected
`algorithm So that the number of path interruptions at which
`the towpreg must be tentatively cut off from the dispensing
`head is minimized.
`
`fabrication of nano
`phased fibers containing oriented nanotubes
`anotubes :
`matrix powder
`
`K.
`
`drive
`
`
`
`
`
`nanotube-containing
`filament or
`nano-phased fiber
`fabrication of a Preform from nano-phased fibers
`
`micron-sized
`orifics
`
`fibers with nanotubes
`of ented along X-direction
`
`* Y .
`
`
`
`fibers with nanotubes
`oriented along Y-direction
`Preform
`fiber with nanotubes oriented
`along fiber axis direction
`
`fabrication of a composite by Consolidating a preform
`?melting the matrix in the
`solidifying the matrix
`nano-phased fiber Ya
`21 nanotubes in
`Neil
`Composite with preferred Y-direction
`pressing all layers together
`anott be orientations
`
`anotubes in X-direction
`
`

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`Patent Application Publication
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`Dec. 25, 2003 Sheet 1 of 17
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`* ``N ·
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`Patent Application Publication Dec. 25, 2003 Sheet 2 of 17
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`US 2003/0236588
`A1
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`Internal Contour
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`Extermal Contour
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`Positive Solid Area
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`F6.2
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`Patent Application Publication Dec. 25, 2003. Sheet 3 of 17
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`Patent Application Publication Dec. 25, 2003. Sheet 4 of 17
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`Publication
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`Patent Application Publication Dec. 25, 2003 Sheet 6 of 17
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`US 2003/0236588
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`Motion
`Controller
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`Patent Application Publication Dec. 25, 2003 Sheet 7 of 17
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`31 O
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`312
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`(A)
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`Patent Application Publicatio
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`Dec. 25, 2003 Sheet 8 of 17
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`F14 7(a)
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`Patent Application Publication Dec. 25, 2003 Sheet 9 of 17
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`Patent Application Publication Dec. 25, 2003 Sheet 10 of 17 US 2003/0236588 A1
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`320
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`(A)
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`Patent Application Publication Dec. 25, 2003. Shee
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`4. 6 (e)
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`Patent Application Publication Dec. 25, 2003 Sheet 12 of 17 US 2003/0236588A1
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`(O)
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`Patent Application Publication Dec. 25, 2003 Sheet 13 of 17
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`360
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`Patent Application Publication Dec. 25, 2003 Sheet 14 of 17
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`f76. 1 (B)
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`Patent Application Publication Dec. 25, 2003. Sheet 15 of 17
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`(BY
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`F16. 10
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`Patent Application Publication Dec. 25, 2003. Sheet 16 of 17
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`A)
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`Patent Application Publication Dec. 25, 2003 Sheet 17 of 17
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`US 2003/0236588A1
`
`data
`Statistical.
`Other rep
`Algebraic
`data
`resentation
`computation
`Preprocess entire:
`Intersect 3-D data with set of mathematical
`Surfaces to calculate set of logical layers
`(with specific thicknesses, outlines and
`material compositions).
`
`Calculate
`logical
`layers
`
`digitizing
`
`Interactive
`processing
`
`Use data from
`(first or) next
`logical layer
`
`
`
`Intersect3-D data with a new
`mathematical surface to calculate
`(first or) next logical layer (with
`specific thickness, outlin &
`material composition).
`
`Generate material deposition paths and hardware control
`command signals according to an ALGORITHM
`Dispense towpreg of correct
`compositions at desired rates
`to predetermined points
`
`Dispense neat matrix
`material at desired flow
`rates .
`
`
`
`Forn
`physical Cut of tOWDreg from dispensing head at points of interruption
`layers
`
`Deposit towpreg of selected compositions to form a layer
`
`(Optional) Deposit a layer of low-melting or weaker
`material (e.g., wax) for the Support structure
`
`Yes
`
`No
`
`(Optional:) Measure current
`-
`r ional:) F
`dimensions to determine
`Final S. tion
`urther unify
`location of next logical layer
`in
`eposited materials
`unification
`N (Optional) Remove support structure
`
`
`
`End
`F16. 2.
`
`

`

`US 2003/0236588A1
`
`Dec. 25, 2003
`
`NANOTUBE FBER REINFORCED COMPOSITE
`MATERALS AND METHOD OF PRODUCING
`FIBER REINFORCED COMPOSITES
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`0001) This application claims the benefit of U.S. Provi
`sional Patent Application Serial No. 60/364,344, filed Mar.
`14, 2002, and U.S. Provisional Patent Application Ser. No.
`60/366,097, filed Mar. 20, 2002, which applications are
`incorporated herein by reference in their entireties for all
`purposes.
`
`STATEMENT REGARDING
`FEDERALLY SPONSORED RESEARCH OR
`DEVELOPMENT
`0002 The development of the present invention received
`financial support from the NSF Partnership for Innovations
`Program and the U.S. NASA Johnson Space Center. The
`U.S. government has certain rights on this invention.
`
`FIELD OF THE INVENTION
`0003. The present invention relates generally to the field
`of materials Science, and more particularly to nanotube
`reinforced composite materials and methods for the produc
`tion of three-dimensional objects composed of continuous
`fiber reinforced composite materials. In particular examples
`of the invention, the nanotubes or nanometer-sized fibrils of
`the material exhibit a controlled degree of preferred orien
`tation. The invention also provides a method of producing
`Such compositions. In other embodiments, the invention is
`related to an improved layer manufacturing or Solid freeform
`fabrication method for producing advanced fiber composite
`objects layer by layer.
`
`BACKGROUND OF THE INVENTION
`0004 Carbon nanotubes are nanometer-scale sized tube
`shaped molecules having the Structure of a graphite mol
`ecule rolled into a rube. A nanotube can be Single-walled or
`multi-walled, dependent upon conditions of preparation.
`Carbon nanotubes typically are electrically conductive and
`mechanically Strong and Stiff along their length. Nanotubes
`typically also have a relatively high aspect ratio (length/
`diameter ratio). Due to these properties, the use of nanotubes
`as reinforcements in composite materials for both Structural
`and functional applications would be advantageous.
`0005. It is well-known in the field of composites that the
`reinforcement fiber orientation plays an important role in
`governing the mechanical and other physical properties of a
`composite material or object. However, it has been found
`that carbon nanotubes typically tend to form a tangled meSS
`resembling a hairball, which is difficult to work with. This
`and other difficulties have limited efforts toward realizing a
`composite material or object containing well-dispersed
`nanotubes with preferred orientations. It is to the provision
`of methods for producing composite materials or objects
`containing well-dispersed nanotubes with preferred orienta
`tions, and to composite materials or objects containing
`well-dispersed nanotube reinforcement with preferred ori
`entations, that certain aspects of the invention are primarily
`directed.
`
`0006 Additionally, several new manufacturing pro
`cesses, commonly referred to as Solid freeform fabrication
`(SFF) or layer manufacturing (LM), have recently emerged
`to build parts point-by-point and layer-by-layer. These pro
`ceSSes were developed for making models, material-proceSS
`ing toolings (e.g., molds and dies), and prototype parts. They
`are capable of producing 3-D Solid objects directly from a
`computer-created model without part-specific tooling or
`human intervention. A SFF process also has potential as a
`cost-effective production proceSS if the number of parts
`needed at a given time is relatively small. Use of SFF may
`reduce tool-making time and cost, and provide the oppor
`tunity to modify tool design without incurring high costs and
`lengthy time delayS. ASFF process can be used to fabricate
`certain types of parts with a complex geometry which
`otherwise could not be made by traditional fabrication
`techniques Such as machining, extrusion and injection mold
`Ing.
`0007 Examples of SFF techniques are stereo lithography
`(SLa), Selective laser Sintering (SLS), 3-D printing, inkjet
`printing, laminated object manufacturing (LOM), fused
`deposition modeling (FDM), etc. SFF technology may be
`divided into three general levels of Sophistication: The first
`is the ability to generate models or prototypes that clearly
`show the part design concept in three dimensions. All or
`most SFF techniques developed So far are capable of cre
`ating Such models. The Second level is the ability to produce
`parts that have acceptable dimensions and tolerances, and
`Sufficient Strength for preliminary evaluation in a simulated
`Service environment. Although Some progress has been
`made in attempting to achieve this ability, parts produced
`without fiber reinforcement, or with only short fibers, typi
`cally lack adequate Structural integrity for many applica
`tions.
`0008. The third level is the ability to produce parts having
`high Structural integrity and good dimensional tolerances,
`Such that they can be placed in real operating Systems. To
`date, little progreSS has been made toward fabricating SFF
`parts with this high level of Structural integrity. Some
`preliminary attempts have been made to use Stereo lithog
`raphy-based techniques to fabricate both short and continu
`ous fiber reinforced, UV-curable resin composites. In most
`cases, only composites with excessively low volume frac
`tions of fibers are obtained using known fabrication methods
`and, hence, the resulting composites have exhibited low
`Strength and Stiffness, insufficient for many applications.
`Furthermore, Such Stereo lithography-based techniques typi
`cally allow use of only a laser-curable or UV-curable resin
`as the matrix material for a composite.
`0009 Fiber reinforced composites are known to have
`great Stiffness, Strength, damage tolerance, fatigue resis
`tance, and corrosion resistance. However, currently avail
`able SFF technologies, in their present forms, typically do
`not lend themselves to the production of continuous fiber
`composite parts. The present invention, however, recognizes
`that Selected SFF approaches (Such as fused deposition
`modeling) can be modified and integrated with textile struc
`ture forming operations (such as Selected fiber-laying steps
`in braiding, weaving and knitting) to produce parts on an
`essentially layer-by-layer basis. The parts produced by Such
`a combination of SFF and textile operations, being of
`continuous fiber reinforced composite, are of Superior Struc
`tural integrity. The new processes of the present invention
`
`

`

`US 2003/0236588A1
`
`Dec. 25, 2003
`
`thus represent a major Step forward toward achieving the
`highest level of Sophistication in SFF.
`0.010 The SFF techniques that potentially can be used to
`fabricate short fiber or particulate reinforced composite parts
`include fused deposition modeling(FDM), laminated object
`manufacturing (LOM) or related lamination-based process,
`and powder-dispensing techniques. AS presently understood,
`the FDM process (e.g., U.S. Pat. No. 5,121,329; 1992 to S.
`S. Crump, incorporated herein by reference) operates by
`employing a heated nozzle to melt and extrude out a material
`Such as nylon, ABS plastic (acrylonitrile butadiene-styrene)
`and wax in the form of a rod or filament The filament or rod
`is introduced into a channel of a nozzle inside which the
`rod/filament is driven by a motor and associated rollers to
`move like a piston. The front end, near a nozzle tip, of this
`piston is heated to become melted; the rear end or Solid
`portion of this piston pushes the melted portion forward to
`exit through the nozzle tip. The nozzle is translated under the
`control of a computer System in accordance with previously
`sliced CAD data to trace out a 3-D object point by point and
`layer by layer. In principle, the filament may be composed
`of a fiber or particulate reinforcement dispersed in a matrix
`(e.g., a thermoplastic Such as nylon). In this case, the
`resulting object would be a short fiber composite or particu
`late composite. The FDM method has been hitherto limited
`to low melting materials. Such as thermoplastics and wax and
`has not been practiced for preparation of metallic parts,
`possibly due to the difficulty in incorporating a high tem
`perature nozzle in the FDM system.
`0011 Modified laminated object manufacturing (LOM)
`has been used to prepare polymer matrix and ceramic matrix
`composites (D. Klosterman, et al, in Proceedings of The 7"
`International Conference on Rapid Prototyping, Mar, 31,
`1997-Apr. 3, 1997, San Francisco, Calif., U.S.A., ed. By R.
`P. Chartoff, et al., pp.43-50 and pp.283-292, incorporated
`herein by reference). AS presently understood, the process
`involves, for instance, feeding, laminating and cutting thin
`sheets of prepregs (preimpregnated fiber preform) in a
`layer-by-layer fashion according to computer-Sliced layer
`data representing croSS Sectional layers of a 3-D object. The
`process cycle typically consists of laminating a Single sheet
`of prepreg to an existing Stack, laser cutting the perimeter of
`the part croSS Section, and laser-dicing or “cubing the waste
`material. After all layerS have been completed, the part block
`is removed from the platform, and the exceSS material is
`removed to reveal the 3-D object This process results in
`large quantities of expensive prepreg materials being
`wasted.
`0012. In U.S. Pat. No. 5,514,232, issued May 7, 1996,
`incorporated herein by reference, Burns discloses a method
`and apparatus for automatic fabrication of a 3-D object from
`individual layers of fabrication material having a predeter
`mined configuration. AS presently understood, each layer of
`fabrication material is first deposited on a carrier Substrate in
`a deposition Station. The fabrication material along with the
`Substrate are then transferred to a Stacker Station. At this
`Stacker Station the individual layers are Stacked together,
`with Successive layers being affixed to each other and the
`Substrate being removed after affixation. One advantage of
`this method is that the deposition Station may permit depo
`Sition of layers with variable colors or material composi
`tions. In real practice, however, transferring a delicate, not
`fully consolidated layer from one Station to another would
`
`typically tend to shift the layer position and distort the layer
`shape. The removal of individual layers from their substrate
`also tends to inflict changes in layer shape and position with
`respect to a previous layer, typically leading to inaccuracy in
`the resulting part.
`0013. In U.S. Pat. No. 5,301.863 issued on Apr. 12, 1994,
`incorporated herein by reference, Prinz and Weiss disclose a
`Shape Deposition Manufacturing (SDM) system. As pres
`ently understood, the System contains a material deposition
`Station and a plurality of processing Stations (for mask
`making, heat treating, packaging, complementary material
`deposition, shot peening, cleaning, Shaping, Sand-blasting,
`and inspection). Each processing Station performs a separate
`function Such that when the functions are performed in
`Series, a layer of an object is produced and is prepared for
`the deposition of the next layer. This System requires an
`article transfer apparatus, a robot arm, to repetitively move
`the object Supporting platform and any layers formed
`thereon out of the deposition Station into one or more of the
`processing Stations before returning to the deposition Station
`for building the next layer. These additional operations in the
`processing Stations tend to shift the relative position of the
`object with respect to the object platform. Further, the
`transfer apparatus may not precisely bring the object to its
`exact previous position. Hence, the Subsequent layer may be
`deposited on an incorrect Spot, thereby compromising part
`accuracy. The more processing Stations that the growing
`object has to go through, the higher the chances are for the
`part accuracy to be lost. Such a complex and complicated
`process typically makes the over-all fabrication equipment
`bulky, heavy, expensive, and difficult to maintain. The
`equipment typically also requires attended operation, adding
`to eXpense.
`0014.
`In the composite manufacturing industry, numer
`ous conventional methods are being practiced to produce
`continuous fiber reinforced composites. All of these methods
`are believed to have disadvantages or shortcomings. For
`example, the hand lay-up process is labor-intensive and the
`quality of the resulting composite part depends highly upon
`the skills of an operator. The combined process of prepreg
`preparation, cutting, lay-up, Vacuum bagging, and autoclave
`or press curing is notoriously tedious, lengthy, and energy
`intensive. In resin transfer molding (RTM), a dry reinforce
`ment material, originally in the forms of roving, mat, fabric,
`or a combination, is cut and shaped into a preform The
`preform is then pre-rigidized by using a Small amount of
`fast-curing resin to hold its shape during the Subsequent
`operations. The preform is then placed in a mold, the mold
`is closed and resin is then injected into it. Resin must flow
`through the Small channels inside a normally tightly-con
`figured preform, expelling the air in the mold cavity, impreg
`nating the preform and wetting out the fibers. The RTM
`process Suffers from Several drawbackS. First, it typically
`requires execution of two separate processes: preform prepa
`ration and resin impregnation. Complete impregnation of a
`dense or large-sized preform by a Viscous resin can be very
`difficult. Second, it typically requires utilization of a mold,
`which is normally quite costly. Third, RTM typically is not
`Suitable for fabricating complex-shaped parts (e.g., part with
`a hollow cavity).
`0015 Processes such as filament winding and pultrusion
`can be highly automated. However, filament winding gen
`erally is essentially limited to fabrication of convex-shaped
`
`

`

`US 2003/0236588A1
`
`Dec. 25, 2003
`
`hollow Structures Such as pressure vessels. Pultrusion can
`produce a variety of reinforced Solid, tubular, or Structural
`profiles. Unfortunately, these Structures are essentially lim
`ited to be of a constant cross-section. Both filament winding
`and protrusion typically are not well-Suited to production of
`complex-shaped parts. Although fiber placement and robotic
`tape-laying techniques can overcome Some of the shortcom
`ings of filament winding, they typically require the utiliza
`tion of expensive, large and heavy equipment. The fiber
`placing or tape laying head is typically of a complex
`configuration and, hence, is easily Subject to malfunction.
`These two techniques typically require highly specialized
`control software that is not usable with any other material
`processing machine. An Overview of various composite
`processing techniques is available in B. Z. Jang, "Advanced
`Polymer Composites: Principles and Applications,” ASM
`International, Materials Park, Ohio, December 1994, incor
`porated herein by reference.
`0016. In summary, currently available SFF technologies,
`generally Speaking, do not lend themselves to the production
`of continuous fiber composite parts. In general, current
`composite processing techniques are not capable of produc
`ing parts of a complex geometry, or producing parts of a
`Specified geometry directly from a computer-aided design.
`Accordingly, it has been found desirable to develop a
`proceSS and apparatus that can be used to fabricate continu
`ous fiber reinforced composite parts of high Structural integ
`rity and complex geometry. It is further desirable that the
`proceSS also has the capability of producing a three-dimen
`Sional object automatically in response to the computer
`aided design of the object. These objectives can be achieved
`to Some extent by the composite layer manufacturing (CLM)
`method of U.S. Pat. No. 5,936,861, Aug. 10, 1999 to Jang,
`et al., incorporated herein by reference. The CLM method
`involves mixing a fiber tow with a Solidifying matrix mate
`rial to form a pre-impregnated tow or “towpreg” and depos
`iting the towpreg point by point and layer by layer on an
`object-Supporting base member.
`0.017. The present invention provides significant
`improvements in many aspects over the method disclosed in
`U.S. Pat. No. 5,936,861. For example, in one aspect, the
`present invention provides an effective method of generating
`the tool path (deposition path) along which a pre-impreg
`nated tow is dispensed and deposited. The method mini
`mizes the requirements for halting the deposition operation
`to cut off the towpreg tentatively from a dispensing nozzle
`and then to re-start the deposition operation at a different
`location.
`
`SUMMARY OF THE INVENTION
`Briefly described, example embodiments of the
`0.018
`present invention provide improved methods of making a
`composite composition or object that includes a matrix
`material and dispersed nanotubes as a reinforcement phase.
`The nanotubes preferably are Substantially aligned along at
`least one Specified axis or direction. The method preferably
`includes: (a) providing a mixture of nanotubes and a matrix
`material in a fluent State, (b) extruding the mixture through
`a Small orifice under a high shear force to form a long or
`continuous-length filament, (c) aligning a Selected number
`of the filament Segments along at least one preferred direc
`tion to form a nanotube-matrix preform, wherein the fila
`ment Segments are Substantially parallel to each other and to
`
`the at least one preferred direction, and (d) consolidating the
`preform to produce the composite composition.
`0019. In this method, the matrix material of the mixture
`can be maintained in either a molten State or Solution State
`(containing a liquid Solvent) So that the mixture is Suffi
`ciently fluent to be extruded out through a Small orifice
`having a diameter preferably in the range of 0.1 um to 50
`tim. Such a high-Shear extrusion results in the formation of
`a continuous filament with nanotubes preferentially aligned
`along the filament axis. A textile operation Such as weaving,
`braiding, knitting, winding, and combinations thereof is then
`executed to align Segments of the resulting filament along at
`least a preferred direction (say, the X-direction of an X-Y-Z
`Cartesian coordinate System) or two preferred directions
`(say, X- and Y-directions) to form a filament preform. The
`preform is then heated to melt out the matrix material with
`the resulting preform preSSurized or compressed into a
`desired shape, which is then followed by cooling to solidify
`the matrix material. This Step is similar to the consolidation
`Step of a traditional textile Structural composite.
`0020. The composite composition is composed of a
`matrix material and preferably 0.5% to 50% by volume of
`nanotubes with the nanotubes having their length or elongate
`axis being Substantially parallel to each other along at least
`one specified direction or axis. Preferably, at least 50% out
`of the nanotubes have their elongate axis being inclined at an
`angle of 15 degrees or less with respect to the at least one
`Specified direction or axis. In one preferred embodiment, the
`Structure of the composite is composed of at least two layers
`with the first layer containing nanotubes aligned predomi
`nantly along a first specified direction or axis (e.g., X-di
`rection) and Second layer containing nanotubes aligned
`predominantly along a Second specified direction or axis
`(e.g., Y-direction). In a three-directional composite, the
`nanotubes have their elongate axis being along at least three
`Specified directions or axes. The matrix material may be, for
`example, Selected from the group consisting of organic,
`polymeric, metallic, ceramic, glass, carbonaceous materials
`and/or combinations thereof.
`0021. In other embodiments, the present invention pro
`vides a method for building a complex-geometry composite
`object essentially point-by-point and layer-by-layer. The
`process preferably includes: (1) combining a reinforcement
`fiber tow with a solidifying matrix material to form a
`pre-impregnated tow (hereinafter referred to as towpreg),
`and (2) dispensing the towpreg at a controlled rate from a
`dispensing head (nozzle) onto a base member or a preceding
`layer already deposited on this base member in a predeter
`mined Sequence to form a multiple-layer object. This
`Sequence is preferably determined by first creating a geom
`etry (drawing) to represent the shape and dimension of a
`desired three-dimensional (3-D) object. The geometry data
`file, comprising essentially a collection of point coordinates
`and vectors, is then Sliced into a number of logical layers
`with each layer having a predetermined thickneSS and croSS
`Section. These layer data are then Sorted out and organized
`into a proper Sequence to define the deposition paths of the
`dispensing head. These deposition path data are Subse
`quently converted to become programmed Signals by a
`computer-aided design computer and Supporting Software
`programs. These programmed Signals define the dispensing
`and deposition paths of the towpreg in an essentially point
`by-point and layer-by-layer fashion. The dispensing of the
`
`

`

`US 2003/0236588A1
`
`Dec. 25, 2003
`
`towpreg and the Solidification of the matrix are permitted to
`occur in Such a manner that the newly deposited towpreg
`Segment is bonded to a previously deposited Segment and
`the new layer is bonded to a previous layer to form a
`multiple-layer object.
`0022. Other embodiments of the present invention pro
`vide new and useful ways of Sorting and organizing layer
`data for a more efficient deposition of a towpreg. These
`Sorting and organizing algorithms are advantageous due to
`the fact that the towpreg is a continuous Strand of fibers and
`a Solidifying matrix material. After a Solid area on a layer
`cross-section is formed, the dispensing head (nozzle) typi
`cally must traverse from this finished area to a new area to
`re-initiate the dispensing and deposition procedure. Before
`Such a traversal from one area to another occurs, the towpreg
`at the last finishing point typically must be cut off So that the
`towpreg will not continue to be pulled out of the dispensing
`nozzle; otherwise, this could result in erroneous or redun
`dant deposition of towpreg along the traversal line. The
`towpreg will come out of the nozzle again when it is ready
`to start building a different area. Such points of Scission or
`interruption preferably must be kept to a minimum in order
`to achieve a more efficient and accurate deposition opera
`tion.
`0023 Drive means such as electric motors are preferably
`provided to Selectively move the base member and dispens
`ing head relative to each other in a predetermined pattern
`along the “X” and “Y” axes of an X-Y-Z Cartesian coordi
`nate System as the towpreg material is being dispensed to
`form each Successive layer. In this coordinate System, the X
`Y plane is defined by a first (X-) direction and a second (Y-)
`direction that are mutually perpendicular. Individual layers
`of the 3-D object being built lie substantially parallel to the
`X-Y plane. The thickness direction of these layers is
`perpendicular to the X-Y plane and is parallel to the
`Z-direction. AS desired, movements along a specific angle
`with “X” or “Y” axis may be executed during the formation
`of each layer. Also as desired, relative vertical movements
`along the “Z” axis may be carried out during the formation
`of each layer, as well as at the completion of each layer to
`achieve a desired layer shape (Surface profile) and thickness.
`0024. Such mechanical movements are preferably
`achieved through programmed Signals inputted to the drive
`motorS for the base member and the dispensing head from a
`computer or controller-Supported by a computer-aided
`design/computer-aided manufacturing System. Such a CAD/
`CAM System preferably contains Software to design and
`create the object to be formed. Specifically, the software is
`preferably utilized to convert the 3-D shape of an intended
`object into multiple layer data. However, Software to convert
`the multiple layer data to programmed Signals through a
`controller to the drive motors for dispensing the towpreg at
`a controlled rate along a predetermined deposition path is
`not known to commercially available at present. Thus, the
`present invention provides methods for generating efficient
`deposition paths of a dispensing nozzle in a predetermined
`Sequence. In order to facilitate a clear description of the
`present invention, relevant terms are described as follows:
`0025) 3-D Solid Model: A solid model is a geometric
`representation (drawing) of a 3-D object. The model
`preferably contains information about the shape and
`dimensions of the object. A 3-D solid model may be
`
`created by using a computer-aided design (CAD)
`approach, reverse engineering, topological informa
`tion and/or mathematical equations, etc.
`0026.
`Slicing: A 3-D solid model can be sliced into
`a plurality of constituent layers with each layer
`having its own cross-sectional shape (profile and
`dimensions) and a layer thickness. The cross-sec
`tional shape can be defined by a set of points, line
`Segments, curves and/or other geometry entities in
`the X-Y plane. The data Specifying Such a layer
`contains a predetermined number of (x,y) coordi
`nates at a given Z value. In many cases, the layer data
`also contains additional information Such as vectors
`that define the orientation of a geometry entity (e.g.,
`the normal to a triangle, direction of a line Segment
`and nature of a contour). The fact that each layer has
`a finite thickness value often leads to the opinion that
`Such a layer represents a 2.5 dimensional entity.
`0027 Contour: Contours represent the boundaries of
`various Solid areas and empty areas (holes) within a
`layer. They may be classified as internal (interior)
`and external (exterior) contours (see FIG. 2). For a
`correct interpretation of the geometry data, each
`Contour must be closed and must not interSect itself
`or another contour.
`0028 Raster segments: In each layer, one may draw
`a set of parallel Straight lines along a Selected direc
`tion (e.g., along the X-axis direction as indicated in
`FIG. 7B). Each of these parallel lines normally
`interSect with a contour at two points, except at the
`contour extremities. These points of interSection may
`be connected to form a set of Successive line Seg
`ments, each having a start point and an end point
`(e.g., FIG. 7C). The purpose of defining these raster
`Segments is to determine the deposition paths of a
`material dispensing nozzle for physically forming
`individual layers of a 3-D object.
`0029 Path interruption: Path interruption is a loca
`tion