Grid structure with sinuous interstices

• US 5,356,692 A
• Filed: 07/27/1992
• Issued: 10/18/1994
• Est. Priority Date: 07/27/1992
• Status: Expired due to Fees

• Current Assignee: Lockheed Missiles and Space Co Inc (Martin Marietta Corporation)
• Original Assignee: Lockheed Missiles and Space Co Inc (Martin Marietta Corporation)
• Inventors: Perez, John M.
• Primary Examiner(s): Nelson, Peter A.
• Application Number:
  US07/922,613
• Time in Patent Office: 813 Days
• Field of Search: 428/116, 428/83, 428/53, 428/113, 118/33, 139/11, 139/380, 139/429, 427/171, 427/172, 427/177, 427/178
• US Class Current: 428/116
• CPC Class Codes: B29C 33/30 Mounting, exchanging or centering moulds, mould parts or cores; B29C33/485 takes precedence
• CPC Class Codes: B29C 33/485 cores or mandrels collapsible mandrels for shaping tube ends B29C57/02; collapsible mandrels for winding and joining B29C53/824
• CPC Class Codes: B29C 70/16 using fibres of substantial or continuous length non-woven fabrics per se D04H3/00
• CPC Class Codes: B29C 70/205 the structure being shaped to form a three-dimensional configuration
• CPC Class Codes: B29C 70/446 Moulding structures having an axis of symmetry or at least one channel, e.g. tubular structures, frames
• CPC Class Codes: B29D 28/005 Reticulated structure comprising reinforcements of substantial or continuous length
• CPC Class Codes: B29K 2063/00 Use of EP, i.e. epoxy resins or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2307/00 Use of elements other than metals as reinforcement
• CPC Class Codes: B64G 99/00 Subject matter not provided for in other groups of this subclass
• CPC Class Codes: E01D 15/14 Floating bridges, e.g. pontoon bridges landing bridges E01D15/24; floating bodies or pontoons B63B
• CPC Class Codes: E01D 2101/40 Plastics
• CPC Class Codes: E04C 2/427 Expanded metal or other monolithic gratings
• CPC Class Codes: Y10T 428/24149 Honeycomb-like

Abstract

A grid structure with sinuous interstices comprises intersecting grid sections having undulate surfaces. The intersecting grid sections of the grid structure are made of a composite material consisting of fibers (e.g., graphite fibers) embedded in a matrix (e.g., epoxy resin).

Claims

1. A method of fabricating a grid structure having sinuous interstices defined by intersecting grid sections, said intersecting grid sections having specified undulate surfaces, said method comprising:

a) arranging filamentary material according to a predetermined pattern to form generally planar intersecting grid sections;

b) inserting cocoons made of filamentary material into corresponding interstices defined by said generally planar intersecting grid sections, the filamentary material of said cocoons in said interstices extending transversely with respect to the filamentary material that is arranged to form said generally planar intersecting grid sections;

c) inserting expandable mandrels into corresponding cocoons, said mandrels having undulate surfaces conforming generally to the undulate surfaces specified for the intersecting grid sections of the grid structure that is to be fabricated;

d) expanding said mandrels within said corresponding cocoons so as to compress the filamentary material of said cocoons together with the filamentary material arranged to form said generally planar intersecting grid sections, said mandrels when expanded thereby converting said compressed filamentary material into intersecting grid sections with undulate surfaces, the undulate surfaces of said intersecting grid sections conforming generally to the undulate surfaces specified for the intersecting grid sections of the grid structure that is to be fabricated;

e) causing said compressed filamentary material that has been converted into said intersecting grid sections with undulate surfaces to be impregnated substantially uniformly with a matrix material;

f) causing said matrix material that has impregnated said compressed filamentary material to cure, thereby forming said grid structure having sinuous interstices; and

g) removing said mandrels from said sinuous interstices after said matrix material has cured.

2. The method of claim 1 wherein the arranging of filamentary material according to a predetermined pattern to form generally planar intersecting grid sections comprises winding a filament made of a fibrous material on a loom according to said predetermined pattern.

3. The method of claim 1 wherein each of said cocoons comprises a sheet consisting of filamentary fibers;

and wherein the inserting of said cocoons into corresponding interstices defined by said generally planar intersecting grid sections is accomplished by spreading said sheets of filamentary fibers within said corresponding interstices so that each sheet is in contact with surface portions of the generally planar intersecting grid sections that define the corresponding interstice.

4. The method of claim 1 wherein each of said expandable mandrels comprises:

a) a plurality of die-plate components held together by spring means to form an elongate hollow structure, said die-plate components having undulate surface portions forming outer surfaces of said hollow structure; and

b) an expander bolt extending longitudinally into said hollow structure;

and wherein the inserting of said expandable mandrels into corresponding cocoons in said interstices formed by said generally planar intersecting grid sections is performed while said mandrels are in a relaxed configuration in which said hollow structures have transverse dimensions that are smaller than corresponding transverse dimensions of said interstices.

5. The method of claim 4 wherein the expanding of each of said mandrels within said corresponding cocoons is accomplished by moving the expander bolt within said hollow structure of each of said mandrels so as to force said die-plate components laterally outward, the undulate surfaces of said die-plate components thereby causing the corresponding cocoon in the corresponding interstice to come into contact with said surface portions of the generally planar intersecting grid sections that define said corresponding interstice.

6. A grid structure comprising a plurality of grid sections that intersect each other to define interstices, said intersecting grid sections having undulate surfaces.

7. The grid structure of claim 6 wherein said intersecting grid sections interpenetrate each other in a manner that maintains substantially uniform weight distribution throughout said grid structure.

8. The grid structure of claim 6 wherein said grid sections are formed from a composite material consisting of fibers embedded in a matrix.

9. The grid structure of claim 8 wherein said fibers consist essentially of graphite fibers.

10. The grid structure of claim 9 wherein said matrix consists essentially of epoxy resin.

11. The grid structure of claim 6 wherein said intersecting grid sections intersect each other at angles that determine a specified configuration for said grid structure.

12. The grid structure of claim 11 wherein said intersecting grid sections intersect each other at right angles.

13. A grid structure having sinuous interstices defined by intersecting grid sections, said intersecting grid sections having specified undulate surfaces, said grid structure being fabricated by a process comprising:

a) arranging filamentary material according to a predetermined pattern to form generally planar intersecting grid sections;

b) inserting cocoons made of filamentary material into corresponding interstices defined by said generally planar intersecting grid sections, the filamentary material of said cocoons in said interstices extending transversely with respect to the filamentary material that is arranged to form said generally planar intersecting grid sections;

c) inserting expandable mandrels into corresponding cocoons, said mandrels having undulate surfaces conforming generally to the undulate surfaces specified for the intersecting grid sections of the grid structure that is to be fabricated;

d) expanding said mandrels within said corresponding cocoons so as to compress the filamentary material of said cocoons together with the filamentary material arranged to form said generally planar intersecting grid sections, said mandrels when expanded thereby converting said compressed filamentary material into intersecting grid sections with undulate surfaces, the undulate surfaces of said intersecting grid sections conforming generally to the undulate surfaces specified for the intersecting grid sections of the grid structure that is to be fabricated;

e) causing said compressed filamentary material that has been converted into said intersecting grid sections with undulate surfaces to be impregnated substantially uniformly with a matrix material;

f) causing said matrix material that has impregnated said compressed filamentary material to cure, thereby forming said grid structure having sinuous interstices; and

g) removing said mandrels from said sinuous interstices after said matrix material has cured.

14. The grid structure of claim 13 wherein the arranging of filamentary material according to a predetermined pattern to form generally planar intersecting grid sections comprises winding a filament made of a fibrous material on a loom according to said predetermined pattern.

15. The grid structure of claim 13 wherein each of said cocoons comprises a sheet consisting of filamentary fibers;

and wherein the inserting of said cocoons into corresponding interstices defined by said generally planar intersecting grid sections is accomplished by spreading said sheets of filamentary fibers within said corresponding interstices so that each sheet is in contact with surface portions of the generally planar intersecting grid sections that define the corresponding interstice.

16. The grid structure of claim 13 wherein each of said expandable mandrels comprises:

a) a plurality of die-plate components held together by spring means to form an elongate hollow structure, said die-plate components having undulate surface portions forming outer surfaces of said hollow structure; and

b) an expander bolt extending longitudinally into said elongate hollow structure;

and wherein the inserting of said expandable mandrels into corresponding cocoons in said interstices formed by said generally planar intersecting grid sections is performed while said mandrels are in a relaxed configuration in which said hollow structures have transverse dimensions that are smaller than corresponding transverse dimensions of said interstices.

17. The grid structure of claim 16 wherein the expanding of each of said mandrels within said corresponding cocoons is accomplished by moving the expander bolt within said hollow structure of each of said mandrels so as to force said die-plate components laterally outward, the undulate surfaces of said die-plate components thereby causing the corresponding cocoon in the corresponding interstice to come into contact with said surface portions of the generally planar intersecting grid sections that define said corresponding interstice.

18. An apparatus for fabricating a grid structure that has sinuous interstices defined by intersecting grid sections, said intersecting grid sections having undulate surfaces, said apparatus comprising:

a) a loom comprising;

(i) a base member; and

(ii) a plurality of posts mounted on said base member, said posts being fixedly positioned with respect to each other so that filamentary material wound around said posts according to a predetermined pattern forms generally planar intersecting grid sections that define interstices into which hollow cocoons made of filamentary material can be inserted;

b) a plurality of comb plates, each of said comb plates having tooth portions with gaps between adjacent tooth portions, said comb plates being dimensioned for placement with respect to said posts so that portions of the filamentary material wound around said posts extend through said gaps between adjacent tooth portions of said comb plates;

c) a plurality of expandable mandrels insertable into the hollow cocoons in corresponding interstices defined by said generally planar intersecting grid sections, said mandrels when expanded causing the filamentary material wound around said posts and the filamentary material of said hollow cocoons to be compressed together so as to form intersecting grid sections having undulate surfaces;

d) a top plate securable to said comb plates so as to bear against said mandrels, said top plate having a closable aperture through which a matrix material can be introduced to impregnate the compressed filamentary material forming the intersecting grid sections having undulate surfaces;

e) means for applying force to said top plate so as to cause said mandrels to expand, thereby compressing the filamentary material wound around said posts and the filamentary material of said hollow cocoons so as to form the intersecting grid sections having undulate surfaces; and

f) means for applying force to said comb plates so as to compress the filamentary material wound around said posts and the filamentary material of said hollow cocoons.

19. The apparatus of claim 18 wherein said base member is configured so as to define a central aperture;

and wherein said posts are mounted on said base member adjacent said central aperture so that the generally planar intersecting grid sections formed from the filamentary material wound around said posts are formed within a volume over the central aperture of said base member.

20. The apparatus of claim 19 further comprising a floor plate, said floor plate being dimensioned so that a peripheral portion of said floor plate can be supported on a portion of said base member circumjacent the central aperture, said floor plate thereby forming a bottom for the volume over the central aperture of said base member;

said comb plates being securable to said floor plate, said comb plates being positionable between said posts and the central aperture so that said comb plates form sides for the volume over the central aperture of said base member;

said top plate forming a top for the volume over the central aperture of said base member;

said top plate together with said comb plates and said floor plate forming a box enclosing the volume over the central aperture of said base member, said box containing the compressed filamentary material forming the intersecting grid sections having undulate surfaces.

21. The apparatus of claim 18 wherein each of said expandable mandrels comprises:

(a) a plurality of die-plate components held together by spring means to form an elongate hollow structure, said die-plate components having undulate surface portions forming outer surfaces of said hollow structure; and

(b) an expander bolt extending longitudinally into said hollow structure, said expander bolt being movable so as to cause said die-plate components to move laterally outward, thereby causing the outer surfaces of said hollow structure to press the corresponding cocoon in the corresponding interstice into contact with surface portions of the generally planar intersecting grid sections that define the corresponding interstice, said die-plate components thereby compressing the filamentary material wound around said posts and the filamentary material of said cocoons together so as to convert the filamentary material into the intersecting grid sections having undulate surfaces.

22. The apparatus of claim 18 wherein said means for applying force to said top plate comprises hydraulic means.

23. The apparatus of claim 18 wherein said means for applying force to said comb plates comprises:

a) sliding members positioned on said base member;

b) pressure pads secured to said sliding members so as to bear against said comb plates; and

c) means for moving said sliding members along said base member so that said pressure pads exert forces on said comb plates.

24. The apparatus of claim 20 wherein the central aperture of said base member is of generally square configuration, and wherein said floor plate is likewise of square configuration dimensioned to be received within the central aperture of said base member.

25. The apparatus of claim 24 further comprising tubular columns secured to corner portions of said floor plate, said comb plates being s secured to said tubular columns to form sides for the volume over the central aperture of said base member.

26. The apparatus of claim 18 wherein said die-plate components forming each elongate hollow structure comprise four corner components and four wedge components, said four corner components being positioned with respect to each other to function as corners of said hollow structure, each of said wedge components being positioned between a corresponding pair of said corner components;

and wherein said expander bolt is movable so as to cause said wedge components to move laterally outward until an undulate surface portion of each wedge component is flush with undulate surface portions of adjacent corner components.

27. The apparatus of claim 18 in combination with means for curing the matrix material impregnating the compressed filamentary material forming the intersecting grid sections with undulate surfaces, said intersecting grid sections with undulate surfaces thereby becoming said grid structure having sinuous interstices.

28. The apparatus of claim 20 in combination with means for removing said box containing the compressed filamentary material forming the intersecting grid sections having undulate surfaces from said loom.

29. The apparatus of claim 28 in combination with means for curing the matrix material impregnating the compressed filamentary material forming the intersecting grid sections with undulate surfaces within said box, said intersecting grid sections with undulate surfaces thereby becoming said grid structure having sinuous interstices.

30. A system for fabricating a grid structure having sinuous interstices defined by intersecting grid sections, said intersecting grid sections having undulate surfaces, said apparatus comprising:

a) a loom comprising;

(i) a base member defining a central aperture; and

(ii) a plurality of posts fixedly positioned with respect to each other adjacent the central aperture of said base member so that filamentary material wound around said posts according to a predetermined pattern forms generally planar intersecting grid sections within a volume over the central aperture of said base member, said generally planar intersecting grid sections defining interstices in which hollow cocoons of generally cylindrical configuration made of filamentary material can be inserted;

b) a floor plate dimensioned so that a peripheral portion of said floor plate can be supported on a portion of said base member circumjacent the central aperture of said base member, said floor plate thereby forming a bottom for the volume over the central aperture of said base member;

c) a plurality of comb plates securable to said floor plate, each of said comb plates having tooth portions with gaps between adjacent tooth portions, said comb plates being dimensioned for placement between said posts and the central aperture of said base member so that said comb plates form sides for the volume over the central aperture of said base member, portions of said generally planar intersecting grid sections extending from the volume over the central aperture of said base member through said gaps between adjacent tooth portions of said comb plates so as to wind around said posts;

d) a plurality of expandable mandrels insertable into the hollow cocoons in corresponding interstices defined by said generally planar intersecting grid sections within the volume over the central aperture of said base member, each mandrel comprising;

(i) a plurality of die-plate components held together by spring means to form an elongate hollow structure, said die-plate components having undulate surface portions forming outer surfaces of said hollow structure of the mandrel; and

(ii) an expander bolt extending longitudinally into said hollow structure of the mandrel, said expander bolt being movable so as to cause said die-plate components to move laterally outward, thereby causing the outer surfaces of said hollow structure of the mandrel to press the corresponding cocoon in the corresponding interstice into contact with surface portions of the generally planar intersecting grid sections that define the corresponding interstice, said die-plate components thereby compressing the filamentary material of said cocoons together with the filamentary material arranged to form said generally planar intersecting grid sections so as to convert the compressed filamentary material to intersecting grid sections with undulate surfaces;

e) a top plate securable to said comb plates, said top plate forming a top for the volume over the central aperture of said base member, said top plate together with said comb plates and said floor plate forming a box enclosing the volume over the central aperture of said base member, said box containing the compressed filamentary material forming the intersecting grid sections with undulate surfaces, said top plate having a closable aperture through which a matrix material can be introduced into the volume over the central aperture of said base member so as to impregnate the compressed filamentary material forming the intersecting grid sections with undulate surfaces;

f) means for applying force to said top plate so as to cause said top plate to move the expander bolts within said hollow structures of said mandrels, thereby causing said die-plate components of said mandrels to move laterally outward so as to compress the filamentary material of said cocoons together with the filamentary material arranged to form said generally planar intersecting grid sections;

g) means for applying force to said comb plates so as to compress the filamentary material of said cocoons together with the filamentary material arranged to form said generally planar intersecting grid sections;

h) means by which said box containing the compressed filamentary material forming the intersecting grid sections with undulate surfaces can be removed from said loom; and

i) means for curing the matrix material impregnating the intersecting grid sections with undulate surfaces within said box, said intersecting grid sections with undulate surfaces thereby becoming said grid structure having sinuous interstices.

31. The apparatus of claim 30 wherein said posts are fixedly positioned with respect to each other adjacent the central aperture of said base member so that the filamentary material wound around said posts forms generally planar intersecting grid sections of generally square transverse cross-sectional configuration.

32. The apparatus of claim 30 wherein said posts are secured to a frame member positioned beneath said base member, said posts extending through post holes in said base member adjacent the central aperture of said base member.

33. The apparatus of claim 30 wherein said floor plate has a plurality of openings that are dimensioned and positioned with respect to each other to receive bottoms portions of corresponding mandrels inserted into the hollow cocoons in corresponding interstices defined by said generally planar intersecting grid sections within the volume over the central aperture of said base member.

34. The apparatus of claim 30 wherein said means for applying force to said comb plates comprises:

a) sliding members positioned on said base member;

b) pressure pads secured to said sliding members so as to bear against said comb plates; and

c) means for sliding said sliding members along said base member so that said pressure pads exert forces on said comb plates.

35. The apparatus of claim 30 wherein the central aperture of said base member is of generally square configuration, and wherein said floor plate is likewise of square configuration dimensioned to be received within the central aperture of said base member.

36. The apparatus of claim 35 further comprising tubular columns secured to corner portions of said floor plate, said comb plates being secured to said tubular columns to form sides for the volume over the central aperture of said base member.

37. The apparatus of claim 30 wherein said die-plate components forming each elongate hollow structure comprise four corner components and four wedge components, said four corner components being positioned with respect to each other to function as corners of said hollow structure, each of said wedge components being positioned between a corresponding pair of said corner components;

and wherein said expander bolt is movable so as to cause said wedge components to move laterally outward so that an undulate surface portion of each wedge component is flush with undulate surface portions of adjacent corner components.

38. A method of forming a pattern for use in fabricating die-plate components having undulate surfaces, said method comprising:

a) placing a plurality of substantially identical wafers on a base member to form a stack of said wafers, a proximal end of a stem member of specified transverse cross section being secured to said base member, each of said wafers having a central aperture that is larger than the specified transverse cross section of said stem member, said wafers being positioned one on top of another on said base member so that said stem member passes through the central aperture of each of said wafers;

b) transversely displacing said stacked wafers by different amounts with respect to said stem member so that surface portions of said stack assume undulate configurations corresponding to the undulate surfaces specified for the die-plate components to be fabricated; and

c) securing a fastening means to a distal end of said stem member so as to secure said wafers rigidly with respect to each other in said stack so that said surface portions of said stack retain said undulate configurations corresponding to the undulate surfaces specified for the die-plate components to be fabricated.

39. A pattern for use in fabricating die-plate components having specified undulate surfaces, said pattern comprising:

a ) a base member;

b) an elongate stem member of specified transverse cross section, a proximal end of said stem member being secured to said base member;

c) a plurality of wafers that are substantially identical to each other, each of said wafers having a central aperture that is larger than the specified transverse cross section of said stem member, said wafers being positioned one on top of another on said base member so that said stem member passes through the central aperture of each of said wafers, said wafers thereby forming a stack, said wafers being transversely displaced by different amounts with respect to said stem member so that surface portions of said stack assume undulate configurations corresponding to the undulate surfaces specified for the die-plate components to be fabricated; and

d) fastening means secured to a distal end of said stem member so as to secure said wafers rigidly with respect to each other in said stack so that said surface portions of said stack retain said undulate configurations corresponding to the undulate surfaces specified for the die-plate components to be fabricated.

40. A spreading tool for insertion into a cocoon positioned in an interstice defined by generally planar intersecting grid sections, said spreading tool being laterally expandable to press portions of said cocoon into contact with corresponding portions of said intersecting grid sections defining corner portions of said interstice, said spreading tool comprising:

a) four corner components and four wedge components held together by spring means to form an elongate hollow structure, said four corner components being positioned with respect to each other to function as corners of said hollow structure, each of said wedge components being positioned between a corresponding pair of said corner components; and

b) an expander bolt extending longitudinally into said hollow structure, said expander bolt being movable so as to cause said four corner components to move laterally outward, thereby pressing said portions of said cocoon into contact with said corresponding portions of said intersecting grid sections.

41. An assemblage of interlocking grid structures, each of said grid structures comprising a plurality of grid sections that intersect each other to define sinuous interstices, said intersecting grid sections having undulate surfaces.

42. The assemblage of interlocking grid structures of claim 41 wherein the intersecting grid sections of each grid structure interpenetrate each other in a manner that maintains substantially uniform weight distribution throughout the grid structure.

43. The assemblage of interlocking grid structures of claim 41 wherein the intersecting grid sections of each of said grid structures are formed from a composite material consisting of fibers embedded in a matrix.

44. The assemblage of interlocking grid structures of claim 43 wherein said fibers consist essentially of graphite fibers.

45. The assemblage of interlocking grid structures of claim 44 wherein said matrix consists essentially of epoxy resin.

46. The assemblage of interlocking grid structures of claim 41 wherein the intersecting grid sections of each of said grid structures intersect each other at angles that determine a specified configuration for said grid structure.

47. The assemblage of interlocking grid structures of claim 46 wherein said intersecting grid sections intersect each other at right angles.

48. The assemblage of interlocking grid structures of claim 41 further comprising buoyant material contained within at least some of said sinuous interstices, and a substantially water-tight covering over said grid structures, said assemblage thereby being usable as a pontoon bridge.

49. The assemblage of interlocking grid structures of claim 41 wherein said grid structures are arranged with respect to each other in a configuration appropriate for deployment in extraterrestrial space.