Abstract
A method of manufacturing a core for a production process and to a core manufactured in accordance with the method are provided. The method includes providing a mold containing a soluble substance and one or more fibers and causing the soluble substance to solidify around the one or more fibers.
Claims
1. A method of manufacturing a core for a production process, comprising: providing a mold containing a soluble substance and one or more fibers; and causing the soluble substance to solidify around the one or more fibers.
2. The method of manufacturing the core of claim 1, wherein the soluble substance is a salt or another water-soluble substance and the one or more fibers are water insoluble; or wherein the soluble substance is soluble by a solvent selected from the group consisting of water, alcohols, petrol, aromatic compounds, acetone or aqueous acids/leaches or a mixture of these and the one or more fibers are insoluble in the solvent.
3. The method of manufacturing the core of claim 1, further comprising: using the core to produce an article; and dissolving the soluble substance in a solvent; wherein the article does not dissolve in the solvent.
4. The method of manufacturing the core of claim 1, wherein the production process is a molding process, an additive manufacturing process, 3D printing, automated fiber placement with in-situ consolidation, automated tape laying, dry or wet filament winding, braiding, or preforming of a composite part; and/or wherein the method further comprises producing an article by using the core in the production process, wherein the core is insoluble in a material of the article.
5. The method of manufacturing the core of claim 1, wherein the one or more fibers have a length of more than 1 mm, more than 2 mm, more than 3 mm, more than 4 mm, more than 5 mm, more than 6 mm, more than 7 mm, more than 8 mm, more than 9 mm, more than 10 mm, more than 20 mm, more than 30 mm, more than 40 mm, more than 50 mm, more than 60 mm, more than 70 mm, more than 80 mm, more than 90 mm, more than 100 mm, more than 200 mm, more than 300 mm or more than 1000 mm; and/or wherein the one or more fibers form a textile or roving.
6. The method of manufacturing the core of claim 1, further comprising: determining a targeted value of a physical property of at least a part of the core, wherein the physical property is selected from the group consisting of a thermal expansion coefficient of the part, a thermal conductivity of the part, a bending strength of the part, a crack sensitivity of the part, a resistance to thermo-shock of the part and a maximum strain the part is capable of withstanding; and selecting the soluble substance, a material of the one or more fibers, a length of the one or more fibers and a mass fraction of the material in accordance with the targeted value.
7. The method of manufacturing the core of claim 6, wherein a least one of, the material of the one or more fibers, the length of the one or more fibers and the mass fraction of the material differ between different parts of the core in accordance with differing targeted values of the physical properties of the parts.
8. The method of manufacturing the core of claim 1, wherein the mold contains solid particles of the soluble substance dispersed in a saturated solution comprising the substance and its solvent.
9. The method of manufacturing the core of claim 1, further comprising: withdrawing vapor from the mold through a gas-permeable and/or liquid-permeable porous structure; and/or exposing the saturated solution to a reduced-pressure atmosphere.
10. The method of manufacturing the core of claim 1, further comprising: heating the soluble substance; wherein the soluble substance is caused to solidify around the one or more fibers by cooling the soluble substance.
11. The method of manufacturing the core of claim 1, wherein the one or more fibers are selected from the group consisting of aramid fibers, carbon fibers, glass fibers, ceramic fibers, basalt fibers, natural fibers and metal fibers.
12. A core, comprising: a matrix formed by a soluble substance; and one or more fibers embedded in the matrix.
13. The core of claim 12, wherein the one or more fibers have a length of more than 1 mm, more than 2 mm, more than 3 mm, more than 4 mm, more than 5 mm, more than 6 mm, more than 7 mm, more than 8 mm, more than 9 mm, more than 10 mm, more than 20 mm, more than 30 mm, more than 40 mm, more than 50 mm, more than 60 mm, more than 70 mm, more than 80 mm, more than 90 mm, more than 100 mm, more than 200 mm, more than 300 mm or more than 1000 mm; and/or. wherein a fiber volume ratio is above 0.05, 0.1, 0.2, or 0.3.
14. The core of claim 12, wherein at least one of, a material of the one or more fibers and a length of the one or more fibers, differ between different parts of the core; and/or wherein the one or more fibers are unevenly distributed within the core.
15. The core of claim 14, further comprising: an attachment portion, wherein the one or more fibers are concentrated around the attachment portion.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0052] The foregoing aspects and many of the attendant advantages will become more readily appreciated as the same becomes better understood by reference to the following description of embodiments, when taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts throughout the various views, unless otherwise specified.
[0053] FIG. 1 schematically illustrates a fiber-reinforced core according to a first example.
[0054] FIG. 2 schematically illustrates a modification of the fiber-reinforced core of FIG. 1.
[0055] FIG. 3 schematically illustrates a fiber-reinforced core according to a second example.
[0056] FIG. 4 schematically illustrates a modification of the fiber-reinforced core of FIG. 3.
[0057] FIG. 5 schematically illustrates a fiber-reinforced core according to a third example.
[0058] FIG. 6 schematically illustrates a fiber-reinforced core according to a fourth example.
[0059] FIG. 7 and FIG. 8 schematically illustrate the usage of one of the fiber-reinforced cores of FIG. 1 to FIG. 6 in a process of manufacturing a molded article.
[0060] FIG. 9 schematically illustrates removing one of the fiber-reinforced cores of FIG. 1 to FIG. 6 from a molded article.
[0061] FIG. 10 schematically illustrates drying the dissolved soluble substance.
[0062] FIG. 11 schematically illustrates milling and sieving the dissolved soluble substance.
[0063] FIG. 12 schematically illustrates a system for manufacturing a fiber-reinforced core for molding according to a first example.
[0064] FIG. 13 schematically illustrates a system for manufacturing a fiber-reinforced core for molding according to a second example.
[0065] FIG. 14 schematically illustrates a system for manufacturing a fiber-reinforced core for molding according to a third example.
[0066] FIG. 15 schematically illustrates a system for manufacturing a fiber-reinforced core for molding according to a fourth example.
[0067] FIG. 16 shows steps of a process for manufacturing a fiber-reinforced core.
[0068] Notably, the drawings are not drawn to scale and unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0069] FIG. 1 shows core 10 which is reinforced by fibers 12. Fibers 12 may have a length of more than 1 mm. Fibers 12 are embedded in matrix 14 which is formed by soluble substance 16 (e.g., a water-soluble alkali salt) that has solidified (crystallized) around fibers 12. The fiber material and the mass fraction of the fiber material may be determined based on a targeted strength, a targeted thermal expansion coefficient, and a targeted thermal conductivity of core 10. To this end, the selected fiber material may exhibit a substantially lower thermal expansion coefficient than soluble substance 16, and a substantially higher thermal conductivity than soluble substance 16. For example, the selected fiber material may exhibit a thermal expansion coefficient which is (at room temperature) 10% lower than a thermal expansion coefficient of soluble substance 16, and a thermal conductivity which is (at room temperature) 10% higher than a thermal conductivity of soluble substance 16. The mass fraction may be between 0.01 and 0.7 and preferably between 0.1 and 0.5.
[0070] Core 10 comprises attachment portion 18 for attaching core 10 to a mold (as will be discussed in more detail further below with regard to FIG. 7). Attachment portion 18 has recess 20, into which a pin of the mold can be inserted. Although core 10 is shown with only one attachment portion 18, core 10 may comprise multiple attachment portions 18 (e.g., attachment portions 18 at opposite sides of core 10). Moreover, attachment portion 18 may be modified in various ways including having a cubical shape as opposed to the cylindrical shape shown in the example. Likewise, the shape of core 10 may be modified depending on the internal shape or features of the article to be molded. For example, core 10 may not have a cylindrical shape as shown in FIG. 1 but a cubical shape, a shape of a bent tube, or any other shape.
[0071] As shown in FIG. 2, fibers 12 may be unevenly distributed within core 10 as opposed to being evenly distributed within core 10, as in FIG. 1. The uneven distribution may serve to particularly increase a strength of a part or portion of core 10 which is expected to experience relatively high stress during molding. As illustrated in FIG. 2, attachment portion 18 may be particularly strengthened. The uneven distribution may also serve to particularly increase a strength of a part or portion which would otherwise be substantially weaker than other parts or portions of core 10. The uneven distribution may further serve to improve a heat transport throughout core 10. For example, a relatively thin part or portion of core 10 may comprise relatively more fibers 12 than a relatively thick part or portion of core 10, to avoid that the relatively thin part or portion breaks during molding and/or to avoid that the relatively thin part or portion becomes a bottle neck with regard to heat transport. This may also serve to reduce tension in core 10 caused by an uneven temperature distribution during molding.
[0072] As shown in FIG. 3, fibers 12 may be aligned. For example, an orientation of fibers 12 that are relatively close to each other may be nearly parallel, whereas an orientation of fibers 12 which are relatively far from each other may not. The alignment of fibers 12 may be beneficial if forces acting on core 12 during molding can be countered by the tensile strength of fibers 12. In other words, the alignment of fibers 12 may cause a longitudinal axis of fiber 12 to be perpendicular to a crack that would otherwise occur if fiber 12 would not counteract the (tensile) forces causing the crack.
[0073] As shown in FIG. 4, fibers 12 may be unevenly distributed within core 10 as opposed to being evenly distributed within core 10, as in FIG. 3, irrespective of the fact that some or all of fibers 12 may be aligned. An uneven distribution may be achieved by avoiding a migration of fibers 12 between different core 12 segments (e.g., due to viscosity) or segmenting core 10 using one or more fiber-impermeable barriers. As shown in FIG. 5, an uneven distribution may also be achieved by connecting fibers 12 to form one or more yarns and/or connecting fibers 12 (or the yarns) to form three-dimensional structure 22. Notably, three-dimensional structure 22 may also be formed by a single fiber or filament. For example, three-dimensional structure 22 may be 3D-printed and integrated into core 10. As shown in FIG. 6, core 10 may also comprise only a single fiber 12 or filament that particularly reinforces a portion of core 12. For instance, single fiber 12 may be wound or braided around attachment portion 18 to particularly increase its strength.
[0074] As shown in FIG. 7 and FIG. 8, core 10 may be attached to part 24 of mold 26. To this end, part 24 comprises protruding portion 28 that fits into recess 20 of attachment portion 18. After assembling mold 26, material 30 may be flown or injected through part 32 into mold 26. After material 30 has hardened, mold 26 may be disassembled and molded article 34 may be removed from part 24 by pushing molded article 34 out of part 24 using rod 36. Rod 36 may be pushed against core 10 to avoid damage to molded article 34. After molded article 34 is removed from part 24, water-soluble substance 16 of core 10 may be dissolved with water as schematically illustrated in FIG. 9. As shown in FIG. 9, water or steam may be flown through nozzle 38 into opening 40 of molded article 34 and soluble substance 16 may be washed out of molded article 34. Fibers 12 may be removed from solution 42 by sieve 44, for reuse or disposal.
[0075] As shown in FIG. 10, solution 42 may be heated by heating device 46 until all solvent has evaporated from solution 42 and soluble substance 16 has solidified. Soluble substance 16 may then be milled with mill 48 and sieved with sieve 50 as shown in FIG. 11. The size of sieve 50 may be 125 μm. (Milled and sieved) soluble substance 16 may be mixed with water or a saturated (aqueous) solution of the soluble substance 16. After adding one or more of fibers 12, slurry 52 (comprising the mixture and one or more fibers) may be placed into mold 54, as shown in FIG. 12. If fibers 12 form a textile, mixture and textile layers may be stacked. Mold 54 may have a top portion which is covered by membrane 56. Membrane 56 may be solvent-permeable and gas-permeable or solvent-impermeable and gas-permeable. Mold 54 may be placed in gas-impermeable hull 58 and porous structure 60 may connect membrane 56 to a discharge opening in hull 58. If hull 58 is evacuated (to a pressure of about 5 mbar), porous structure 60 may avoid that a gas flow (towards vacuum pump) is obstructed by hull 58. To accelerate evaporation, a temperature of slurry 52 may be maintained at 60° C. Moreover, a pressure outside hull 58 may be increased (above 1 bar) to accelerate the process and to improve the resistance of core 10 against forces acting on core 10.
[0076] As shown in FIG. 13, mold 54 may be provided with die 62 that can be urged against slurry 52 to squeeze solvent out of slurry 52 and to make the core which is formed once slurry 52 solidifies around fibers 12, more resistant to forces acting on core 10. Die 62 or any other section of mold 54 may be porous to increase a rate at which solvent and vapor are removed from mold 54. Otherwise, solvent and vapor may be removed through the clearance between die 62 and matrix 64. As shown in FIG. 14, mold 54 may comprise two dies 62 to apply the pressure more evenly to the slurry 52. Both dies 62 may be similar and their setup may be the same. Once, soluble substance 16 solidifies around fibers 12, core 10 may be removed from mold 54.
[0077] Or, as shown in FIG. 15, soluble substance 16 may be heated (to about 700° C. at a pressure of about 300 MPa, if soluble substance 16 is an alkali salt) and subsequently cooled-down. Otherwise, mold 54 may be directly filled with a (dry) powder of soluble substance 16 (without using the steps described in connection with FIG. 12, FIG. 13, and FIG. 14 to generate a green body), soluble substance 16 may be melted (e.g., slowly heated in an inert atmosphere, to avoid tool and fiber degradation, such as a nitrogen atmosphere, an argon atmosphere, a vacuum, etc. to about 900° C., if soluble substance 16 is an alkali salt) and subsequently cooled-down. Once soluble substance 16 solidifies around fibers 12, core 10 may be removed from mold 54. In another example, soluble substance 16 may be injected into mold 54 (at a temperature of more than 800° C., if soluble substance 16 is an alkali salt) and then cooled down. After having removed core 10 from mold 54, core 10 may be used to manufacture molded article 34 as describe above.
[0078] FIG. 16 shows steps of the process for manufacturing core 10. The process starts at step 66 with providing mold 54 containing soluble substance 16 and one or more fibers 12. The process continues at step 68 with causing soluble substance 16 to solidify around one or more of fibers 12.
REFERENCE SIGNS LIST
[0079] 10 core [0080] 12 fibers [0081] 14 matrix [0082] 16 soluble substance [0083] 18 attachment portion [0084] 20 recess [0085] 22 three-dimensional structure [0086] 24 part (bottom of mold) [0087] 26 mold [0088] 28 protruding portion [0089] 30 material [0090] 32 part (top of mold) [0091] 34 molded article [0092] 36 rod [0093] 38 nozzle [0094] 40 opening [0095] 42 solution [0096] 44 sieve [0097] 46 heating device [0098] 48 mill [0099] 50 sieve [0100] 52 slurry [0101] 54 mold [0102] 56 membrane [0103] 58 pouch [0104] 60 porous structure [0105] 62 die [0106] 64 matrix [0107] 66 step [0108] 68 step
