Nanotube fiber reinforced composite materials and method of producing fiber reinforced composites

• US 20030236588A1
• Filed: 03/14/2003
• Published: 12/25/2003
• Est. Priority Date: 03/14/2002
• Status: Active Grant

• Current Assignee: Auburn University
• Original Assignee: Auburn University
• Inventors: Li, Zhimin M., Chen, Shizhu, Jang, Bor Z., Mahfuz, Hassan, Liu, Jun H., Adnan, Ashfaq
• Granted Patent: US 6,934,600 B2
• Time in Patent Office: Days
• US Class Current: 700/119
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing
• CPC Class Codes: B33Y 30/00 Apparatus for additive manufacturing; Details thereof or accessories therefor
• CPC Class Codes: B33Y 40/00 Auxiliary operations or equipment, e.g. for material handling
• CPC Class Codes: B33Y 50/02 for controlling or regulating additive manufacturing processes
• CPC Class Codes: B33Y 70/10 Composites of different types of material, e.g. mixtures of ceramics and polymers or mixtures of metals and biomaterials
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C04B 2235/5248 Carbon, e.g. graphite
• CPC Class Codes: C04B 2235/5284 Hollow fibers, e.g. nanotubes
• CPC Class Codes: C04B 2235/6026 Computer aided shaping, e.g. rapid prototyping
• CPC Class Codes: C04B 35/62873 Carbon
• CPC Class Codes: C04B 35/62889 with a discontinuous coating layer
• CPC Class Codes: Y10S 977/753 with polymeric or organic binder

Abstract

A composite composition and a method of making such a composite that is composed of a matrix material and dispersed 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 controller 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.

Claims

1. A method of making a composite material comprising:

providing a mixture of nanotubes and a matrix material in a fluent state;

extruding said mixture to form a filament wherein said nanotubes are aligned along a filament axis;

aligning a plurality of segments of said filament in a first direction to form a nanotube-matrix filament perform; and

consolidating said preform.

2. The method of claim 1 wherein the matrix material of said mixture is in a molten state.

3. The method of claim 1 wherein said mixture contains a liquid solvent.

4. The method of claim 1 wherein said filament is extruded through an orifice having a diameter between about 0.1 μ

m to about 50 μ

m.

5. The method of claim 1 further comprising aligning segments of said filament in a second direction to form the nanotube-matrix filament perform.

6. The method of claim 5 further comprising aligning segments of said filament in a third direction to form the nanotube-matrix filament perform.

7. The method of claim 1 wherein said aligning step comprises weaving, braiding, knitting, winding, or combinations thereof.

8. The method of claim 1 wherein said consolidating step comprises heating, pressurizing, and solidifying said matrix material.

9. A composite material comprising a matrix material and 0.5% to 50% by volume of nanotubes, wherein said nanotubes are aligned substantially parallel to each other along a first specified direction.

10. The composite material of claim 9, wherein at least 50% of said nanotubes have their elongate axis inclined at an angle of 15 degrees or less with respect to said first specified direction.

11. The composite material of claim 9, comprising at least two layers, a first layer containing nanotubes aligned predominantly along the first specified direction and a second layer containing nanotubes aligned predominantly along a second specified direction.

12. The composite material of claim 9, wherein said matrix material is selected from organic, polymeric, metallic, ceramic, glass, carbonaceous materials and combinations thereof.

13. A method of forming a composite material comprising:

providing a mixture of nanotubes and a matrix material in a fluent state;

extruding the mixture through an orifice to form a continuous filament;

segmenting said filament to form filament segments;

aligning a first plurality of the filament segments in a first direction to form a first perform layer;

aligning a second plurality of the filament segments in a second direction generally perpendicular to the first direction to form a second perform layer; and

consolidating the first and second perform layers.

14. A method for making a continuous fiber-reinforced composite material-based three-dimensional object, comprising:

combining a reinforcement fiber tow with a solidifying matrix material to form a preimpregnated tow or towpreg;

providing a dispensing head capable of dispensing said towpreg onto a surface area of a base member positioned a distance from said dispensing head;

said dispensing head and said base member being driven by motion means electronically connected to a motion controller regulated by a computer; and

operating and moving said dispensing head relative to said base member to dispense-multiple layers of towpreg;

said steps of operating and moving comprising the following sub-steps;

creating a geometry file of said object on a computer with said geometry comprising a plurality of layers and each said layer being composed of a plurality of thin segments which can be connected to form exterior and interior contours for delineating respectively the exterior and interior boundaries of a cross-sectional shape of said layer;

converting said geometry to form deposition paths along which said dispensing head is driven to trace out individual layers by following a selected algorithm so that the number of path interruptions at which said towpreg must be cut off from said dispensing head is minimized;

converting said deposition paths into programmed signals in a predetermined sequence; and

in response to said programmed signals received from said computer, operating and moving said dispensing head to deposit multiple layers of towpreg, one upon another, in said sequence to form said 3-D object.

15. The method of fabricating a 3-D fiber composite object of claim 14, further comprising:

establishing an X-Y-Z Cartesian coordinate system defined by three mutually perpendicular X, Y -and Z-axes with each said layer lying approximately parallel to an X- Y plane;

for each said layer, defining positive solid areas with each said solid area being an area enclosed by an external contour of said layer excluding those areas enclosed by corresponding internal contours if any; and

for each said layer, generating said deposition paths in such a fashion that the towpreg dispensed from said dispensing head approximately covers at least one of said positive solid areas entirely.

16. The method for fabricating a 3-D fiber composite object of claim 14, wherein said algorithm comprises:

establishing an X-Y-Z Cartesian coordinate system defined by three mutually perpendicular X-, Y -and Z-axes with each said layer lying parallel to an X-Y plane;

for each said layer, defining positive solid areas with each said solid area being an area enclosed by an external contour of said layer excluding those areas enclosed by any corresponding internal contours; and

for each said layer, generating said deposition paths such that the towpreg dispensed from said dispensing head covers one of said positive solid areas only partially.

17. The method of claim 15, wherein the generation of said deposition paths comprises following a raster segment method comprising:

drawing a set of parallel straight lines on said cross-sectional shape of a layer along a selected direction on an X- Y plane;

each said straight line intersecting one of said contours at two points;

connecting said points of intersection to form a set of successive line segments or raster segments, each having a start point and an end point forming a vector in such a fashion that the end point of a vector is at a predetermined short distance from the start point of a neighboring vector; and

defining said deposition paths by allowing said dispensing head to trace out said raster segments consecutively.

18. The method of claim 16, wherein the generation of said deposition paths comprises following a raster segment method comprising:

drawing a set of parallel straight lines on said cross-sectional shape of a layer along a selected direction on an X- Y plane;

each said straight line intersecting one of said contours at two points;

connecting said points of intersection to form a set of successive line segments or raster segments, each having a start point and an end point forming a vector in such a fashion that the end point of a vector is at a predetermined distance from the start point of a neighboring vector; and

defining said deposition paths by allowing said dispensing head to trace out said raster segments consecutively.

19. The method of claim 14, wherein said parallel lines are substantially equally spaced and the spacing between two neighboring lines is approximately equal to the width of said towpreg.

20. The method of claim 14, wherein said algorithm comprises cutting off said towpreg at a point of interruption.

21. The method of claim 20, wherein said towpreg cutting is executed by using a tool selected from a laser beam, a sharp blade, a pair of scissors, a milling machine, a heated wire and an electrical discharging wire.

22. The method of claim 15, wherein the initial position of said dispensing head is at the origin of said Cartesian coordinate system and said algorithm includes additional steps of locating extremity points of said contours having a minimum or maximum X- or Y-coordinate value and permitting said dispensing head to start the deposition of said towpreg at a selected extremity point.

23. The method of claim 16, wherein the initial position of said dispensing head is at the origin of said Cartesian coordinate system and said algorithm includes additional steps of locating extremity points of said contours having a minimum or maximum X- or Y-coordinate value and permitting said dispensing head to start the deposition of said towpreg at a selected extremity point.

24. The method of claim 15, wherein the generation of said deposition paths comprises following a raster segment method comprising:

drawing a set of parallel straight lines on said cross-sectional shape of a layer along a selected direction on an X-Y plane;

each said straight line intersecting one of said contours at two points;

connecting said points of intersection to form a set of successive line segments or raster segments, each having a start point and an end point forming a vector in such a fashion that the end point of a vector is at a predetermined distance from the start point of a neighboring vector; and

defining said deposition paths by allowing said dispensing head to trace out said raster segments according to the following sequence of sub-steps;

selecting a first raster segment in a first positive solid area with the start point of said segment being an extremity point having a minimum or maximum X-or Y coordinate value;

directing said dispensing head to begin the deposition of said towpreg from said first extremity point to the end point of said first raster segment;

if the start point of a next neighboring raster segment lies on the same contour as the end point of said first raster segment, moving said dispensing head to the start point of this neighboring raster segment and trace out said neighboring segment;

otherwise, cutting off said towpreg at the end point of said first segment and move said head to the start point of another raster segment having a minimum or maximum X-or Y-coordinate value, re-starting the towpreg deposition to trace out said another segment;

repeating the previous step until said first solid area is traced out;

moving said dispensing head to another solid area and subsequent solid areas and repeating the preceding sub-steps until all solid areas are traced out.

25. The method of claim 14, wherein said algorithm comprises forming a deposition path by a contour offset method comprising:

defining positive solid areas for each said layer with each said solid area being an area enclosed by an external contour of said layer excluding those areas enclosed by corresponding internal contours if any;

positioning said dispensing head to a first start point of first exterior contour of a solid area and operating said head to deposit said towpreg along said first exterior contour from said first start point to a first end point;

moving said head inward by a off-set distance to a second start point and operating said head to deposit said towpreg along a second curve substantially parallel to said first exterior contour from said second start point to a second end point;

moving said head further inward by a off-set distance to another start point and operating said head to deposit said towpreg along another curve substantially parallel to said second curve from said another start point to another end point; and

repeating the preceding step until said head reaches a desired point inside said solid area.

26. The method of claim 14, wherein said algorithm comprises forming a deposition path by a contour offset method comprising:

defining positive solid areas for each said layer with each said solid area being an area enclosed by an external contour of said layer excluding those areas enclosed by corresponding internal contours if any;

positioning said dispensing head to a first start point of an interior contour for a solid area and operating said head to deposit said towpreg along said first interior contour from said first start point to a first end point;

moving said head outward by a off-set distance to a second start point and operating said head to deposit said towpreg along a second curve substantially parallel to said first interior contour from said second start point to a second end point;

moving said head further outward by a off-set distance to another start point and operating said head to deposit said towpreg along another curve substantially parallel to said second curve from said another start point to another end point; and

repeating the preceding step until said head reaches a desired point on the exterior contour of said solid area.

27. The method of claim 14, wherein said algorithm comprises forming a deposition path in a spiral fashion.

28. The method of claim 14, wherein said algorithm comprises forming a deposition path by a sub-area method comprising:

establishing an X- Y -Z Cartesian coordinate system defined by three mutually perpendicular X-, Y- and Z-axes with each said layer lying approximately parallel to an X- Y plane;

for each said layer, defining positive solid areas with each said solid area being an area enclosed by an exterior contour of said layer excluding those areas enclosed by corresponding interior contours if any;

locating convex portions of an exterior contour and/or concave portions of an interior contour with each said portion having at least two extremum points and/or one point of inflection;

drawing a line tangent to one said portion at a first of said extremum points with said tangent being extended to intersect said portion at a first point of intersection, said first extremum point and said first point of intersection forming a first boundary line;

drawing a second boundary line from a second of said extremum points to intersect said first boundary line at a second point of intersection;

said first and second extremum points being such that if one is a maximum the other is a minimum and said second point of intersection intersecting no other point on said contour portion;

the curve segment of said contour portion bounded by said first extremum point and said first point of intersection along with said first and second boundary lines defining two sub-areas; and

obtaining a deposition path in such a fashion that said dispensing head being directed to trace out one of said sub-area first and then trace out the other said sub-area.

29. The method of claim 14, wherein said programmed signals comprising signals in terms of standard NC G-codes and/or M codes commonly used in computerized numerical control machining industry.

30. The method of claim 14, wherein said algorithm comprises a strategy that, if two or more said positive solid areas corresponding to two or more components of said object exist and the space between neighboring components is sufficiently large to accommodate said dispensing head, said dispensing head and said motion means may be operated to build one said component to a desired thickness first before moving to build a second component.

31. The method of claim 14, further comprising:

evaluating said geometry data files representing said object to locate any un-supported feature of said object;

defining a support structure for an un-supported feature and creating a plurality of thin segments defining said support structure;

generating program signals corresponding to each of said segments for said support structure in a predetermined sequence; and

operating a material-depositing tool to form said support structure layer by layer.

32. The method of claim 14, wherein said towpreg can be oriented along a different direction in different regions of a layer or in different layers.

33. The method of claim 14, further comprising additional steps of dispensing said towpreg along a Z-axis direction at predetermined locations.

34. The method of claim 14, wherein said towpreg can be of different types and can be dispensed along a different direction in different regions of a layer or in different layers.

35. The method method of claim 14, wherein the moving step comprises:

moving said dispensing head and said base member relative to one another in a direction parallel to an X-Y plane, defined by two mutually perpendicular X-and Y coordinate axes, to form a first layer of said towpreg on said base member;

moving said head and said base member away from one another in a third or Z-axis direction perpendicular to said X-Y plane by a predetermined layer thickness; and

after the portion of said first layer adjacent to said head has substantially solidified, dispensing a second layer of said towpreg materials onto said first layer while simultaneously moving said base member and said head relative to one another in a direction parallel to said plane, whereby said second layer solidifies and adheres to said first layer.

36. The method of claim 35, further comprising forming multiple layers of said towpreg on top of one another by repeated dispensing and depositing of said towpreg from said head as said base member and said head are moved relative to one another in a direction parallel to said plane, with said head and said base member being moved away from one another in said third direction by a predetermined layer thickness after each preceding layer has been formed and with the depositing of each successive layer being controlled to take place after said deposited materials in the preceding layer immediately adjacent said head have substantially solidified.

37. The method of claim 14, wherein each of said thin segments is coded with a material composition and said towpreg-dispensing head is provided with at least another material dispensing tool for depositing another towpreg material or another solidifying material.

38. The method of claim 37, wherein said moving step includes the step of moving said head and said base member relative to one another in a direction parallel to said plane according to a first predetermined pattern to form an outer boundary from at least one of said towpreg materials on said base member, said outer boundary defining an exterior surface of said object.

39. The method of claim 38, wherein said outer boundary defines an interior space in said object, and said moving step further includes the step of moving said dispensing head and/or said at least material dispensing tool relative to said base member in one direction parallel to said plane according to at least one other predetermined pattern to fill said interior space with said towpreg or said another solidifying material.

40. The method of claim 39, wherein said interior space is deposited with a spatially controlled material composition comprising two or more distinct types of materials.

41. The method of claim 40, wherein said distinct types of materials are deposited at discrete locations in three-dimensional part space to form a spatially controlled material composition part.

42. The method of claim 14, further comprising

using dimension sensor means to periodically measure dimensions of the object being built;

using a computer to determine the thickness and outline of individual layers of said towpreg deposited in accordance with a computer aided design representation of said object;

said computer being operated to calculate a first set of logical layers with specific thickness and outline for each layer and then periodically recalculate another set of logical layers after comparing the dimension data acquired by said sensor means with said computer aided design representation in an adaptive manner.