METHOD FOR PRODUCING A CERAMIC FIBER COMPOSITE COMPONENT

Description

[0001] The present invention relates to a method for manufacturing a ceramic fiber composite component.

[0002] Carbon fiber reinforced silicon carbide ceramic materials combine the properties of carbon fibers and a ceramic SiC matrix. This results in a material with high hardness, high wear resistance, high fracture toughness, low thermal expansion, and excellent chemical resistance at high temperatures. Ceramic brake discs made of carbon fiber reinforced silicon carbide ceramic materials are now in series production. However, manufacturing is very complex, and the production of particularly intricate components is very time-consuming, material-intensive, and therefore costly.

[0003] Additive manufacturing techniques such as 3D printing enable a high degree of design freedom and the flexible production of small batches. However, powder-based monolithic ceramics are brittle. Incorporating long reinforcing fibers during printing is virtually impossible with conventional 3D printing processes for ceramic powders, such as binder jetting or paste extrusion. This is especially true for fibers whose length exceeds the diameter of the particles used for printing. EP3453505A1 describes a method for producing a composite component. The method involves at least partially covering a core with an organic binder and at least one silicon component with a reinforcing fiber material, wherein the core includes at least one section with a nonlinear geometry. The method includes an infiltration process with a ceramic matrix precursor material, which is polymer impregnation and pyrolise.

[0004] The object of the present invention is to provide a simple and economical method for producing a ceramic fiber composite component with reduced waste, wherein the component with very high hardness, very high wear resistance, and high fracture toughness, high damage tolerance, low thermal expansion and high chemical resistance is made available in any complex shape with little effort.

[0005] This problem is solved by a method according to claim 1.

[0006] The method according to the invention is a method for producing a ceramic fiber composite component and comprises the following steps: a) Providing a carbon-based and / or ceramic, e.g. silicon carbide-based or boron carbide-based body, which has been manufactured by additive manufacturing, b) Treating a reinforcing element and / or the provided body at a temperature of at least 600°C, preferably at least 800°C, particularly preferably at least 1400°C or at least 1600°C before attaching the reinforcing element to the body, c) Attaching a fiber-containing reinforcing element to the body, d) Joining the body and the reinforcing element by infiltration with silicon or with a silicon-containing compound, and e) if in step d) joining by infiltration with a silicon-containing compound is carried out, a subsequent heat treatment in a range above 400°C is performed.

[0007] The temperature treatment in step e) is preferably carried out in a range of 400 to 1200 °C, more preferably in a range of 800 to 1200 °C.

[0008] Silicon carbide forms in the temperature ranges mentioned in step e).

[0009] The body provided in step a) can be a carbon-based body and / or a ceramic body. In principle, any ceramic that can be additively manufactured from a powder (and binder) into a body is suitable, provided it meets the conditions in step d). Preferably, "ceramic" here refers to silicon carbide or boron carbide or mixtures thereof. The body provided in a) can therefore preferably be a carbon-based and / or silicon carbide-based or boron carbide-based body produced by additive manufacturing. In particular, the body provided in a) can be produced by additive manufacturing from a mixture of coke and silicon carbide.The type of coke used is not particularly restricted; cokes such as coal tar pitch coke, petroleum coke, acetylene coke, flexicoke, fluid coke, or shot coke, preferably flexicoke, can be used, among others. The production and the advantageous properties resulting from the use of cokes are described in WO 2017 / 089499 A1. If the body in step a) has been produced by a mixture of carbon and silicon carbide, the ceramic fiber composite component provided according to the invention has a lower weight than a fiber composite component in which only SiC powder was used in step a); these fiber composite components provided according to the invention are more economical due to the lower raw material costs of carbon compared to SiC.The boron carbide ceramic fiber composite components provided according to the invention combine the particular advantages of very low weight, very high hardness, and high fracture toughness. Consequently, the fiber composite components produced according to the invention, starting from boron carbide-based bodies, are ideally suited as ballistic protection for mobile applications, in particular as ballistic protection for personnel.

[0010] The statement that the body is carbon-based and / or ceramic, e.g., silicon carbide-based or boron carbide-based, means that the body consists of at least 50 wt.%, preferably at least 70 wt.%, and most preferably at least 90 wt.% carbon and / or ceramic, e.g., silicon carbide and / or boron carbide. The mass fractions specified here refer to the body as obtained from additive manufacturing, i.e., before the application of the reinforcing element and before infiltration of the body with any further substance. These mass fractions refer to the ratio of the sum of the mass fractions of carbon and ceramic, e.g., silicon carbide and / or boron carbide, to the total mass of the body provided in step a).Since carbon in connection with the present invention refers to amorphous carbon and graphite, the proportion of carbon includes both amorphous carbon and graphite, i.e., any carbon regardless of its degree of crystallinity.

[0011] The body provided in step a) is obtainable or manufactured by additive manufacturing. Certain embodiments of the method according to the invention include additive manufacturing of the body prior to step a). However, it is also possible to use the body obtainable or manufactured by additive manufacturing.

[0012] The bodies provided in step a) can be purchased or manufactured separately from the inventive method in a spatially and / or temporally decoupled manner. The additive manufacturing of the body can therefore optionally be included in the inventive method.

[0013] The body provided in step a) can be purchased or fabricated using the techniques described in WO 2017 / 089494 A1, WO 2017 / 089499 A1, WO 2017 / 089500 A1, WO 2019 / 063831 A2, WO 2015 / 038260 A2, DE 10 2014 216 433 A1, DE 2006 015 014 A1 or DE 10 2012 2019 989A1. It can also be fabricated as described in: Moon J. et al., Fabrication of functionally graded reaction infiltrated SiC-Si composite by three-dimensional printing (3DP™) process, Materials Science and Engineering: A, 31 January 2001, Vol. 298, No. 1-2, pp. 110-119. A wide variety of highly suitable additively manufactured bodies can be purchased from SGL Carbon.

[0014] The body provided in step a) preferably comprises particles with a mean size (d50) in the range of 10–500 µm. The resulting high porosity of the body promotes infiltration in step d), especially when liquid silicon is infiltrated. The laser granulometric method (ISO 13320) can be used to determine the d50 value, employing a measuring device from Sympatec GmbH with associated evaluation software. The particle size in the existing body can be determined from the micrograph, e.g., using light microscopy.

[0015] In preferred processes according to the invention, additive manufacturing is understood to mean binder jetting or paste extrusion. In a particularly preferred process according to the invention, the body provided in step a) has been produced by binder jetting or is obtainable by binder jetting.

[0016] In binder jetting, a powdered base material is bonded with a binder at selected points to create the body. This results in a powder-based, highly porous, largely isotropic, and homogeneous body. Homogeneous in this context means that the formed body has no density gradients, as is the case, for example, with compression molding. The bonding agent penetrates the pores and ensures a firm attachment of the reinforcing element to the body in step c). The infiltration in step d) then creates a particularly strong bond between the reinforcing element and the body. This results in a continuous bonding silicon phase from the base body, through the bonding agent zone, and into the reinforcing element.

[0017] The binder used in binder jetting is referred to herein as the jetting binder. Organic or inorganic jetting binders can be used, with, for example, water glass being suitable as an inorganic jetting binder and, for example, phenolic resin or furan resin being suitable as organic jetting binders. Binder jetting yields a body with a solids content greater than 80% by weight, preferably greater than 90% by weight.

[0018] In paste extrusion, an extrusion paste is deposited in a defined manner and a predetermined pattern to create the body. The extrusion paste can be deposited layer by layer from an extruded strand. The extrusion paste contains carbon particles and / or ceramic particles, e.g., silicon carbide particles. It also contains a binder. The binder used in the extrusion paste is not subject to any particular restrictions. Preferably, the extrusion paste contains a carbonizable binder, e.g., phenolic resin, furan resin, benzoxazine resin, pitch, cellulose, starch, sugar, polyvinyl alcohol (PVA), thermoplastics such as polyacryletherketones and, in particular, polyetheretherketone (PEEK), and / or polyimide.

[0019] The fiber-containing reinforcing element is not subject to any special restrictions. In principle, any fiber, fiber-containing material, or fiber-containing mass can be used as a fiber-containing reinforcing element, provided that it can be further processed with the body according to process steps c) and d) to form a ceramic fiber composite component as provided according to the invention.

[0020] In the context of the present invention, "fiber" preferably means carbon fiber or silicon carbide fiber, particularly preferably carbon fiber. Accordingly, "fiber-containing" preferably means "carbon fiber-containing" or "silicon carbide fiber-containing," particularly preferably "carbon fiber-containing." Compared to silicon carbide fiber, carbon fiber is characterized by higher cost efficiency. However, silicon carbide fiber is more resistant to oxidation than carbon fiber and exhibits a coefficient of thermal expansion that is better suited to the SiC matrix.

[0021] According to the present invention, any method of attaching the reinforcing element to the body is suitable, provided it withstands the conditions prevailing in the subsequent process step d). The reinforcing element is preferably attached to the body using an adhesive. As will become clear from the following descriptions of malleable and rigid fiber-containing reinforcing elements and attachment methods, the adhesive can preferably be the adhesive already contained in the reinforcing element and / or an additionally introduced adhesive.

[0022] The fiber-containing reinforcing element provided in step c) may be malleable. This is generally the case when the fiber-containing reinforcing element contains a binder that has not yet hardened. The fibers may be wetted by the binder or embedded in the binder. Specific examples of such malleable reinforcing elements are: a resin and fiber-containing mass, which is also referred to herein as "resin-fiber mass", a textile fabric at least partially impregnated with resin (such fabrics are available for purchase as "prepregs", e.g. from SGL Carbon) a resin-impregnated fiber strand.

[0023] The resin used for the production of such malleable reinforcing elements has a carbon yield of preferably at least 10%, more preferably at least 20% and more preferably at least 40% after pyrolysis.

[0024] The malleable reinforcing element does not need to contain a binder, unlike braided hoses where a body is woven with fibers. After application, impregnation with a binder can be carried out. This can then be followed by carbonization and then step d).

[0025] The application of these fiber-reinforced elements to the body can then be carried out, for example, by pressing using a press farm (application method 1), spraying using fiber spraying (application method 2), pressing on using a vacuum bag process (application method 3) and / or autoclave process (application method 4), or wrapping the body with the fiber-containing reinforcing element (application method 5). The vacuum bag process and the autoclave process are described in Drechsler, K., Heine, M., Mitschang, P., Baur, W., Gruber, U., Fischer, L., Öttinger, O., Heidenreich, B., Lützenburger, N. and Voggenreiter, H. (2009), Carbon Fiber Reinforced Composites, in Ullmann's Encyclopedia of Industrial Chemistry, (Ed.)., in section 2.3.3. It is self-evident to the expert which of the aforementioned attachment methods 1 to 5 are suitable for the above-listed malleable reinforcement elements for attachment to the body.When a malleable reinforcement element is attached to the body, its shape generally changes. The reinforcement element can be flexibly adapted to the body's contours during application.

[0026] Malleable reinforcement elements allow the shape of the body to be optimized without regard to the shape of a rigid reinforcement element. It is then unnecessary to provide a body with a surface specifically adapted to the surface of a given, rigid reinforcement element. Since the binder, e.g., resin, of malleable reinforcement elements is not yet cured at the moment of application to the body, it can simultaneously serve as an adhesive.

[0027] The fiber-reinforcing element provided in step c) can also be rigid. A fiber-reinforcing element is rigid, for example, if it contains cured binder, a carbon matrix, and / or a ceramic matrix. Specific examples of rigid fiber-reinforcing elements are: Fiber-reinforced carbon elements, e.g., carbon fiber-reinforced carbon elements, in particular: ∘ fiber-reinforced carbon plates, e.g., carbon fiber-reinforced carbon plates (CFC plates); ∘ fiber-reinforced carbon rings, e.g., carbon fiber-reinforced carbon rings (CFC rings); ∘ fiber-reinforced carbon rods, e.g., carbon fiber-reinforced carbon rods (CFC rods); and carbon fiber-reinforced silicon carbide ceramic elements, in particular: ∘ carbon fiber-reinforced silicon carbide ceramic plates; ∘ carbon fiber-reinforced silicon carbide ceramic rings; ∘ carbon fiber-reinforced silicon carbide ceramic rods

[0028] The rigid fiber-containing reinforcement element can also be a fiber-reinforced plastic element, e.g. a carbon fiber-reinforced plastic element.

[0029] These rigid reinforcing elements can be attached to the body by pressing them onto a surface of the body (especially if the rigid reinforcing element is a plate), folding them over the body (especially if the rigid reinforcing element is a ring), or inserting them into a recess in the body (especially if the rigid reinforcing element is a rod, grid, or ring). Since the adhesive of a rigid reinforcing element is generally cured and can no longer serve as a bonding agent, additional bonding agent can be applied to attach the body.

[0030] The bonding agent, which can be supplied to attach the reinforcing element to the body or supplied in addition to a bonding agent contained in the malleable reinforcing element, may, for example, contain a resin, in particular a phenolic resin, a furan resin, a benzoxazine resin, a bismaleimide resin, a sugar, a pitch or an organosilicon compound, such as a silicon-containing polymer, e.g. a polysiloxane, a polycarbosilane, a polysilane or a polysilazane.

[0031] According to the invention, in step b), the reinforcing element and / or the body are treated at a temperature of at least 600 °C, preferably at least 800 °C, particularly preferably at least 1400 °C, e.g., at least 1600 °C, before the reinforcing element is attached to the body. This has the advantage that no or only minimal further pyrolysis occurs during the subsequent infiltration in step d). Part of the shrinkage occurring in step d) is thus anticipated even before the attachment. Furthermore, the heating zone or the furnace in which step d) is generally carried out is thereby very well protected from contamination. Cleaning intervals associated with downtime can be shortened, and thus the ceramic fiber composite components provided according to the invention can be produced even more efficiently.Initial trials clearly indicate that this method also reduces rejects in the production of fiber-reinforced composite components. It is assumed that mechanical stresses in the area of ​​the resulting connection between the body and the reinforcing element are minimized. Therefore, this method enables the production of more stable fiber-reinforced composite components with particularly low reject rates.

[0032] The temperature of at least 1400 °C refers to the melting point of pure silicon and applies in particular when liquid pure silicon is infiltrated in step d). Generally, the reinforcing element and / or body are preferably treated at a pretreatment temperature before the reinforcing element is attached to the body, wherein the pretreatment temperature is at most 300 K, in particular at most 200 K, e.g., at most 100 K below the highest temperature reached in step d).

[0033] The bonding agent can, for example, be a binder that, when heated in a nitrogen atmosphere, has a material yield of at least 20 wt.%, preferably at least 40 wt.%. This is tested by weighing approximately one milliliter of bonding agent, heating it in a nitrogen atmosphere at a heating rate of 1 K / minute up to 900 °C, and then maintaining the sample at 900 °C for a further 10 minutes under a nitrogen atmosphere. The residue is weighed again. If the mass at the second weighing is at least 20% of the mass at the first weighing, the material yield is at least 20 wt.%. Preferably, the mass fractions of carbon and silicon in the residue are at least 40 wt.%, preferably at least 90 wt.%, e.g., at least 95 wt.%. This ensures that silicon carbide forms particularly well in the transition zone between the reinforcing element and the body in process step d).This further increases the strength of the ceramic fiber composite components produced according to the invention. If the bonding agent is a paste as described in more detail in the following paragraph, the above information on material yield refers to the liquid portion of the bonding agent. Solid components are then separated before determining the material yield, e.g., by centrifugation.

[0034] Preferably, the bonding agent is a paste containing carbon and / or silicon carbide particles and / or fibers with an average length of no more than 3 mm, e.g., with a mass fraction of particles and / or fibers of 10–90 wt.%, in particular 30–70 wt.%. The fibers contained in the paste can be, for example, short-cut fibers or ground fibers. Short-cut fibers are produced by cutting numerous sections of equal length from a fiber strand. Ground fibers are produced by grinding fibers.

[0035] The paste harmonizes the thermomechanical properties of the body and the reinforcing element, with the paste's particles and fibers filling the cavities between the contacting surfaces. The thermal stresses occurring between the body and the reinforcing element in step d) then appear to be better absorbed by the forming ceramic fiber composite component. This results in higher mechanical strength and greater dimensional stability of the component.

[0036] Conversely, using less paste helps to maintain dimensional accuracy. Therefore, a person skilled in the art can choose the amount of paste to maximize dimensional accuracy without causing excessive mechanical stress in the resulting composite components.

[0037] Ceramic fiber composite components provided according to the invention, which comprise very large volume fractions attributable to paste, are less preferred. This is because, in the finished ceramic fiber composite component, the areas attributable to paste are generally less load-bearing than the areas attributable to fiber-containing reinforcing elements. Preferably, the bonding agent is a paste that occupies at most 10% of the total volume of the fiber composite component as obtained after step c). The upper limit of 10% specified here refers to bonding agent volumes that are present in addition to any binder optionally contained in the reinforcing element. If several bodies and / or several reinforcing elements are incorporated into the ceramic fiber composite component, all bodies, all reinforcing elements, and all areas attributable to paste are included in the calculation of the relevant volume fractions.

[0038] Before or after step c), the body and / or reinforcing element can be compacted by chemical vapor infiltration (CVI) and / or by infiltration with carbonizable substance and subsequent carbonization (so-called "compaction").

[0039] Carbonization, as defined here, is pyrolysis in a non-oxidizing atmosphere, e.g., in an N2 atmosphere.

[0040] A substance is considered carbonizable if, upon heating in a nitrogen atmosphere, it decomposes into a residue whose carbon content is higher by mass than that of the substance itself. This is tested by heating one milliliter of the substance in a nitrogen atmosphere at a rate of 1 kilominute to 900 °C and then maintaining the sample at 900 °C for another 10 minutes under a nitrogen atmosphere. The carbon content is determined by elemental analysis before and after heating. Examples of carbonizable substances that can be advantageously used for infiltration include phenolic resins, furan resins, benzoxazine resins, bismaleimide resins, sugars (presented as a solution containing at least one sugar), pitch, and mixtures thereof. These carbonizable substances may also contain carbon- and silicon dioxide-based fillers to increase the solids yield.

[0041] A similar compaction could also be achieved with silicon-containing substances that decompose into Si / SiC through pyrolysis.

[0042] The substances used for compaction may also contain fillers based on carbon and SiC to increase the solids yield.

[0043] Compaction by CVI can be carried out, for example, as described in WO 2019 / 063831 A2.

[0044] The compaction process allows the desired porosity for the infiltration in step d) to be achieved. If the compaction is performed after the fiber-containing reinforcement element has been attached to the body, a continuous phase is created that bonds all parts. Furthermore, the compaction ensures a carbon layer on the fibers within the fiber-containing reinforcement element. During the subsequent infiltration, silicon carbide is preferentially formed with the carbon in this carbon layer. The reinforcing fibers, e.g., carbon fibers, are then less susceptible to attack by the infiltration. This increases the mechanical strength of the ceramic fiber composite component provided according to the invention. The compaction process can be repeated.

[0045] Before the compaction process begins, carbonization occurs of any carbonizable substance, such as resins, that may be present in or on the reinforcing element and / or body.

[0046] According to the invention, in step d) the body and the reinforcing element are joined by infiltration with silicon or with a silicon-containing compound. This step is also referred to herein as "silicification". If infiltration with a silicon-containing compound is carried out in step d), a subsequent step e) must be performed to effect complete "silicification" within the meaning of the present invention.

[0047] Infiltration can occur through a liquid or gaseous medium.

[0048] For example, liquid silicon or a liquid containing at least one silicon-containing compound can be infiltrated.

[0049] The liquid silicon need not be pure, as the desired bond between the body and the reinforcing element forms well even if the liquid silicon contains larger quantities of other substances. In particular, the silicon can contain metals such as iron, zirconium, titanium, or aluminum. The silicon mass fraction of the melt used for infiltration with liquid silicon is preferably more than 50 wt.%. However, it can also be pure silicon with a silicon mass fraction of > 95 wt.%, preferably > 97 wt.%, and particularly preferably > 99 wt.%. Due to the high melting point of silicon, silicon carbide generally forms during infiltration, with the carbon contained in the silicon carbide originating from the reinforcing element and the body. This is therefore also referred to as reactive infiltration.In this process, a continuous silicon-containing bonding phase is formed from the body, possibly via the bonding agent zone, into the reinforcing element.

[0050] The silicon-containing compounds in the liquid are preferably organosilicon compounds, in particular polymers, e.g., polysiloxanes, polycarbosilanes, polysilanes, polysilazanes. If a liquid containing silicon-containing compounds is infiltrated, step d) further comprises a temperature treatment following the infiltration under conditions in which silicon carbide is formed, e.g., at a temperature in the range of 400 to 1200 °C, in particular in the range of 800 to 1200 °C.

[0051] Alternatively, a gas containing a vaporizable silicon compound, preferably a vaporizable organosilicon compound, and particularly preferably a vaporizable organosilicon compound with a Si-C bond, such as methylchlorosilane, can be infiltrated. For example, methylchlorosilane can be infiltrated at 1250 °C in a low-pressure H₂ / N₂ atmosphere by chemical vapor infiltration (CVI).

[0052] At the latest in step d) or step e) in the case of silicon-containing compounds, the resulting ceramic fiber composite component is generally exposed to very high temperatures, so that the stress gradients and mechanical stresses mentioned above occur. These arise because the thermally induced expansion of the core and the reinforcing element differ. The thermally induced expansion is superimposed with irreversible shrinkage. This shrinkage is due to the pyrolysis of components of the core and the reinforcing element. Stronger stress gradients and mechanical stresses can always occur when the coefficient of thermal expansion and the shrinkage of the components (core and reinforcing element) differ significantly.

[0053] If the core shrinks considerably more than the reinforcing element when heated, segmentation cracks form in the core. This is because the core is more prone to cracking under thermally induced tensile stress than the fiber-reinforcing element. It was found that the segmentation cracks are randomly shaped but occur at fairly regular intervals, as shown in Figures 8 A, B and D This is clearly visible. The segmentation cracks promote siliconization and are simultaneously filled during the siliconization process. Therefore, they do not represent a significant mechanical weakness, but merely thermal bridges. These can be used to dissipate heat, which is advantageous in many applications.

[0054] It is assumed that the consistently homogeneous structure of the additively manufactured bodies provided in step a) ensures that segmentation cracks form at such regular intervals. The fact that step a) starts with the additively manufactured body thus contributes to the homogeneity of the heat flow across regularly spaced thermal bridges of the component provided according to the invention.

[0055] Since crack formation depends on the thermal shrinkage of the component, the number, spacing, and dimensions of the cracks depend on the extent of shrinkage within the composite. This is significantly influenced by the thermal processes (especially the process temperature) that the component or the powder used in the component has already undergone before joining. If the component provided in step a) is graphite-based, e.g., made from graphite powder, then the shrinkage of the component and thus the mechanical stresses are minimized. Alternatively, the component can be pretreated at a high temperature before joining, or a high-temperature-treated powder can be used in additive manufacturing.

[0056] A body reinforced with a fiber-reinforced element, made from a body pre-tempered at, for example, only 700°C, shrinks much more than a body that was tempered at, for example, 1400°C before joining.

[0057] Furthermore, the location of the segmentation cracks can be controlled by making the body used in step a) weaker at certain points (so-called weak points), so that segmentation cracks form only at these points or predominantly only at these points. Such points can be depressions on the surface of the body or, alternatively, targeted binder-free areas within the additively manufactured body. Figure 8C schematically shows a section through a component provided according to the invention, in which the segmentation cracks (filled by siliconization) are only located at the points where the body provided in step a), obtainable by additive manufacturing, was less developed.

[0058] Introducing numerous such weak points results in the formation of numerous cracks, leading to a narrower crack width compared to randomly formed cracks. Furthermore, cracks can be selectively created at locations where heat conduction channels are advantageous. If the cracks originate during thermal processes prior to step d), the crack volume can be filled with carbon by infiltration of a carbon-containing compound and subsequent pyrolysis. This causes SiC to form within the crack volume during silicon infiltration in step d), resulting in Si / SiC / C filling the cracks in the fiber-reinforced component.

[0059] In step b) of the inventive method, the body and / or the reinforcing element are infiltrated with silicon or with a silicon-containing compound.

[0060] This infiltration can be carried out under the same conditions specified above for step d).

[0061] The optional compaction of the body and / or reinforcing element described above generally takes place before the body and / or reinforcing element is (for the first time) infiltrated with silicon or a silicon-containing compound.

[0062] The problem is also solved by a ceramic fiber composite component obtainable according to the inventive method; e.g. by a ceramic fiber composite component comprising a body and a fiber-containing reinforcing element, wherein the body and the reinforcing element are bonded with Si and / or SiC ceramic, produced according to an inventive method.

[0063] The ceramic fiber composite component provided according to the inventive method comprises a body that is free of fibers or does not include fibers with an average length of more than 0.5 mm and a fiber-containing reinforcing element that includes fibers with an average length of more than 1 mm, wherein the body and the reinforcing element are bonded with Si and / or SiC ceramic.

[0064] In components provided according to the invention, the ratio of the volume of the reinforcing element(s) to the total volume of the component can vary widely. For certain components / applications, very small reinforcing elements may suffice. Conversely, for other components / applications, very large reinforcing elements may be required. In general, the volume ratio of the reinforcing element(s) to the total volume of the component provided according to the invention is 0.001 to 0.80, preferably 0.05 to 0.60, and particularly preferably 0.01 to 0.50.

[0065] The fiber volume fraction in the fiber-containing reinforcing element is preferably at least 20%, and particularly at least 50%. This can be determined optically in the cross-sectional image. For this purpose, a component provided according to the invention, including the reinforcing element, is cut through, the cut surfaces obtained from the cutting are ground, and the proportion of the total reinforcing element cut surfaces occupied by fibers is determined visually (e.g., with a microscope). If the fibers are not completely homogeneously distributed within the reinforcing element, the component is cut through multiple times, and all reinforcing element cut surfaces are included in the determination of the fiber volume fraction.As already described above in connection with the method according to the invention, the production of the ceramic fiber composite component can be carried out using formable reinforcing elements, such as resin-fiber compounds. In particular, such compounds frequently lead to components produced according to the invention with extensive fiber-free, resin-based reinforcing element areas and with a correspondingly low fiber volume fraction.

[0066] Preferably, the body is free of fibers or comprises fibers whose dimensions do not exceed those of the particles from which the body is formed; for example, it does not comprise fibers longer than 0.5 mm, and in particular, no fibers longer than 0.4 mm. This upper limit on fiber length ensures that the body can be produced in a particularly simple manner by additive manufacturing, e.g., binder jetting. Fibers above a certain length are difficult to process in additive manufacturing processes.

[0067] The fiber-containing reinforcing element is preferably a carbon fiber-containing or silicon carbide-containing reinforcing element, particularly preferably a carbon fiber-containing reinforcing element. This results in high impact strength, pseudoductile fracture behavior, high hardness, high wear resistance, good friction properties, high strength, good temperature and corrosion stability, and at the same time inert behavior towards many highly corrosive chemicals, such as hydrochloric, sulfuric, and nitric acid. Ultimately, this leads to a very versatile applicability of the components provided according to the invention, whereby the service life of conventional components is sometimes significantly exceeded. A number of possible uses are given below.

[0068] Preferably, the fiber-containing reinforcing element comprises a woven fabric, a spiral fabric, a multiaxial non-woven fabric, a unidirectional non-woven fabric, short-cut fibers, continuous fibers, a nonwoven fabric, a felt, a paper, a braid, a knitted fabric, an embroidered fabric, and / or a fiber grid. Knitted fabrics are elastic and therefore easily drapeable. Fiber grids provide gaps for good thermal conductivity. The body can then have areas that extend through the fiber grid, so that thermal bridges exist between the front and back of the fiber grid. In general, in components provided according to the invention, the thermal conductivity of the body is higher than the thermal conductivity of the fiber grid. Braids and knitted fabrics are preferably tubes and are therefore well suited for external reinforcement of the body. Reinforcing elements comprising continuous fibers are produced, for example, by wrapping a towpreg around the body.

[0069] According to the invention, the ceramic fiber composite component preferably has a fiber-containing reinforcing element comprising fibers with an average length of more than 1 mm. The aforementioned fiber-containing reinforcing elements, such as nonwovens, fleeces, felts, papers, braids, knitted fabrics, or fiber grids, regularly contain fibers with an average length well over 1 mm.

[0070] The ceramic fiber composite component can have a fiber-containing reinforcing element comprising fibers with an average length of more than 0.5 cm, e.g., more than 1 cm, and especially more than 2 cm. With shorter fibers, fabrics, braids, knitteds, or fiber grids can only be produced with increased effort. However, very short fibers are also possible, particularly with short-cut fibers, nonwovens, felts, or papers.

[0071] A preferred ceramic fiber composite component contains 20–90 wt% SiC and 5–45 wt% free silicon. It may also contain 0–60 wt%, e.g., 5–60 wt% free carbon. This results in high-temperature stability up to 1400°C, as well as high chemical stability (corrosion resistance), wear resistance, good friction properties, toughness, and high thermal conductivity. The mass fractions of Si and SiC can be determined according to DIN EN ISO 21068-2.

[0072] There are no restrictions regarding the shape of the connected surface areas of the reinforcing element and the body. The body can be positively connected to the reinforcing element. This results in an additional increase in the stability of the connection between the parts of the fiber composite component, i.e., between the reinforcing element and the body. At least one of the parts (e.g., the body) can have an undercut into which the other part (e.g., the reinforcing element) positively engages, e.g., in the form of a dovetail joint. This is very effective in connection with the invention, since additive manufacturing is particularly well suited for producing undercuts. The body provided in step a) can therefore have an undercut. A malleable reinforcing element can be positively engaged with the undercut during application, e.g., by pressing, and then cured to form a bond.

[0073] The body can have a recess into which the (entire) fiber-containing reinforcing element is received, or the fiber-containing reinforcing element can have a recess into which the body is received. Another alternative is that the body and the fiber-containing reinforcing element are positively connected. The reinforcing element does not alter the external geometry of the body, or the body does not alter the external geometry of the body. The surface remains unchanged, which can be a significant advantage, for example, in a pump impeller.

[0074] Additive manufacturing allows the body to be produced in a wide variety of shapes, enabling virtually any conceivable fiber composite component geometry. Recesses for fiber-reinforcing elements and / or undercuts can be incorporated at any desired location. Depending on the component and its intended use, particularly high mechanical loads always occur at specific points where the fiber-reinforcing elements can be strategically positioned. Where thermal loads are expected, the body can be provided without fiber reinforcement, since the body of the fiber composite component produced according to the invention generally has a higher thermal conductivity than the fiber-reinforcing element. This results in a component that meets the expected loads (mechanical and thermal) in every area of ​​the component and can be manufactured particularly cost-effectively.

[0075] The body can contain graphite particles. Compared to amorphous carbon, this results in a further increase in the high-temperature stability of the component provided according to the invention. In addition, thermal and chemical stability (corrosion resistance) as well as thermal conductivity are increased.

[0076] The components provided according to the invention do not exhibit spontaneous brittle fracture behavior. Spontaneous brittle fracture behavior is typically exhibited by non-fiber-reinforced ceramics.

[0077] Preferred ceramic fiber composite components provided according to the invention exhibit pseudoductile fracture behavior. This means that, in a three-point bending test, a stress-strain curve can be determined for ceramic fiber composite components provided according to the invention, which, after an initial rise due to the linear-elastic deformation of the component, does not abruptly drop to zero at the first crack. The component does not fail abruptly at the first crack.

[0078] In contrast, for example, a ceramic without fiber reinforcement would break at the end of the linear elastic deformation, resulting in a stress-strain curve in the 3-point bending test which, after an initial increase due to the linear elastic deformation of the component, abruptly falls to 0.

[0079] Such an abrupt drop of the stress-strain curve to zero does not occur with components provided according to the invention, since the fiber-containing reinforcement element connected to the body prevents sudden material failure. Even after an initial crack in the body of the component provided according to the invention, further force is required for further deformation due to the reinforcement element. The pseudoductile fracture behavior gives the ceramic fiber composite component a pronounced damage tolerance.

[0080] The 3-point bending test can be carried out, for example, in accordance with ISO 178:2013 with support radius: 3mm, punch radius: 3mm, span: 80 mm, with a test speed of 2 mm / min.

[0081] Some ceramic fiber composite components exhibit at least one segmentation crack extending from a surface of the body facing the reinforcing element into the body, where the mass fraction of silicon in the segmentation crack is higher than in the areas of the body adjacent to the segmentation crack. This can be determined by energy-dispersive X-ray spectroscopy (EDX).

[0082] The ceramic fiber composite component can have multiple spaced-apart filled segmentation cracks, where the total volume of the segmentation cracks occupies at most 10%, e.g., at most 5%, of the total volume of the body. The total volume of the body is the sum of the body's volume and the volume of the segmentation cracks.

[0083] The ceramic fiber composite components provided according to the invention can be used as brake discs for aircraft, trains, elevators, cable cars, motorcycles, passenger cars, buses, trucks, quads, racing vehicles, for industrial applications, e.g. for cranes or paper machines, as brake pads, as wear protection linings, as clutch discs, as grinding wheel carriers, as heat sinks, as high-temperature housings with cooling fins, as heat exchangers for high temperatures or chemical apparatus, as pump impellers, as turbine components, as burner nozzles, as spray nozzles, as charging aids, as process aids (e.g. as process aids for high-temperature processes, such as hardening, soldering, coating, firing, and forming processes), as casting, pressing, deep-drawing, and laminating machines, as ballistic protection, as satellite dish carriers, or as measuring instruments.

[0084] It is worth emphasizing that this process incurs no or only very minimal additional costs for complex geometries. A significant advantage of the inventive method is that the complex structure can be printed. This results in considerably less waste compared to conventional manufacturing of, for example, ventilation structures, recesses, and channels. The ability to selectively place fibers at the points of highest mechanical stress enables particularly efficient manufacturing, as fibers are more expensive than the raw materials required for additive manufacturing. Further efficiency gains result from the near-net-shape accuracy of additive manufacturing. This reduces post-processing effort and, in particular, the use of diamond-coated abrasives. Furthermore, additive manufacturing usually eliminates the need for mold making to produce complex geometries.

[0085] Fiber reinforcement largely prevents the brittle fracture behavior of the ceramic body that occurs naturally without fiber reinforcement. This is particularly important for rotating components or for ballistic protection, where targeted reinforcement can achieve multi-hit capability.

[0086] Brake discs of all types are safety-critical components. Therefore, ceramic brake discs are now exclusively fiber-reinforced to ensure that spontaneous brittle fracture failure cannot occur. The production of fiber-reinforced brake discs is very complex and severely limits design freedom. By combining 3D-printed cooling structures with fiber-reinforced reinforcement elements, it is possible to manufacture cost-effective brake discs that meet both the mechanical and safety requirements (reinforcement element) as well as the thermal and thermomechanical requirements (3D-printed body).

[0087] Ceramic burner nozzles, spray nozzles, heat exchangers, chemical apparatus, turbine components, and high-temperature housings are frequently subjected to internal pressure during operation. If these components are made entirely of ceramic, i.e., without fiber reinforcement, this can lead to unintended, spontaneous, catastrophic failure, which, for example, prevents the controlled shutdown of an entire system and can result in secondary damage. The hybrid design—a 3D-printed component with a fiber-reinforced reinforcement element—largely eliminates catastrophic failure and the potentially associated secondary damage.

[0088] Clutch discs, grinding wheel carriers, turbine components, and pump impellers are all critical components due to their high rotational speeds. The risk of spontaneous failure is therefore effectively minimized by the hybrid design (3D-printed body plus reinforcement element).

[0089] Wear-resistant linings and ballistic protection structures made of purely monolithic ceramics are at risk of brittle total failure under sudden stress, which can completely destroy the component's integrity. In the case of linings, this can lead to the lining falling into the reactor. In the case of ballistic protection, the component's multi-hit capability can no longer be guaranteed. Attaching the reinforcing element to the 3D-printed body can act similarly to safety glass, thus largely preventing complete component failure.

[0090] Charging aids and process aids also benefit from the hybrid design. Using 3D printing, for example, complex, dimensionally stable tray shapes (e.g., as a negative mold of the component to be hardened or sintered) can be combined with mechanically impact-resistant carrier plates, thereby achieving mechanical robustness for both elements while simultaneously offering a high degree of cost-effective geometric freedom.

[0091] In the case of satellite dish mounts, damage-tolerant fiber-reinforced base structures can be combined with complex, highly rigid 3D-printed rib structures. Similar principles can be applied to measuring instruments, heat sinks, and any type of mold.

[0092] The method according to the invention can also be used to repair ceramic components. For this purpose, a precisely fitting inlay can be produced using 3D printing and inserted into a damaged fiber-reinforced component. Joining can be achieved using an adhesive paste, followed by a temperature step to create a continuous silicon matrix. The method according to the invention can also be used to repair ceramic ballistic plates. In this case, the parts of the ballistic plates damaged by gunfire can be replaced by precisely fitting inlays, allowing these ballistic plates to be reused.

[0093] The invention is illustrated by the following figures and embodiments, without being limited to them. Figures

[0094] Figure 1A shows a sandwich component with a flat reinforcing element between two flat, 3D-printed bodies. Figure 1B shows a sandwich component with a flat, 3D-printed body between two flat reinforcing elements. Figure 1E shows a sandwich component with a flat reinforcing element between two flat, paste-applied 3D-printed bodies. Figure 1D shows a multi-layer component in which flat, 3D-printed bodies and flat reinforcing elements are arranged alternately on top of each other. Figure 1E shows a sandwich component in which the flat 3D-printed body has a continuous recess through which the two flat reinforcing elements are connected. Figure 2A shows a component in which the body has several recesses for receiving a reinforcing element each. Figure 2B shows a section through the component. Figure 2AFigure 2C, shown along the dashed line, depicts a component in which the body has recesses connected to form a grid for receiving a grid-shaped reinforcing element. Figure 2D shows a section through the component. Figure 2C Figure 2E, along the dashed line, shows a section through a multi-layer component consisting of three layers of components made of Figure 2A or 2B Figure 2F shows a component in which the body has a plurality of cylindrical recesses, each for receiving a reinforcing element. Figure 2G shows a section through the component. Figure 2F Along the dashed line, Figure 3A shows a component with a disc-shaped body surrounded by a ring-shaped reinforcing element. Figure 3B shows a section through the component. Figure 3AFigure 3C, shown along the dashed line, depicts a component with a disc-shaped body, wherein an annular reinforcing element is received in a circumferential groove. Figure 3D shows a section through the component. Figure 3C Figure 4A, shown along the dashed line, shows a top view of a component with an upwardly open body filled with a reinforcing element obtainable from a fiber-containing fill. Figure 4B shows a section through the component. Figure 4AAlong the dashed line with lid, Figures 5A, B, and C show sections of bodies whose complexly shaped surface is covered with a reinforcing element. Figures 6A and B show components in which dovetail-shaped reinforcing elements are received in at least one groove. Figures 7A and B show components in which the 3D-printed body contains a channel structure, such as that which can be used for cooling. Figures 8A, B, C, and D show sections of components in which the 3D-printed body has silicon-filled segmentation cracks. Figures 9A and B show a component in which complex 3D-printed bodies are joined to a fiber-reinforced base plate. Figure 9A The supervision shows Figure 9BFigure 10 shows a cross-section through the component. Figure 10 shows a stress-strain curve from a 3-point bending test. Figure 11 shows a cross-section through a composite consisting of a reinforcement element comprising short-fiber carbon fibers with a 3D-printed positioned cooling element.

[0095] In Figures 1A to E The components provided according to the invention are in the form of sandwich structures made of planar reinforcing elements. 2 and planar, 3D-printed bodies 1 are shown. Such sandwich structures are produced by compression molding and subsequently further processed by means of carbonization and siliconization to form a component according to the invention. The type of the respective preferred reinforcing element 2 This depends on the geometry of the component (reinforcing element based on web material for rectangular structures or spiral fabric for round structures) as well as the subsequent load distribution (unidirectional, multiaxial fabrics or woven fabrics).

[0096] In the components of the Figures 1A , B, D and E, an uncured, resin-containing and therefore malleable reinforcing element is used in the manufacturing process. 2 introduced. As a malleable reinforcing element, it can be used to manufacture the components of the Figures 1A For example, in B and D, E, a prepreg is used. The resin contained in the prepreg acts as a bonding agent and ensures a cohesive bond between the body and the material. 1 and reinforcement element 2.

[0097] The component of the Figure 1C It is manufactured using an additional bonding agent. The bonding agent is a paste containing carbon and / or silicon carbide particles. The bonding agent is applied to the interfaces between the body and the reinforcing element. Such a bonding agent may be particularly necessary for rigid reinforcing elements to bond the reinforcing element. 2 firmly attached to the body 1to be applied. The component provided according to the invention is produced by carbonization and siliconization with liquid silicon, wherein the bonding agent is infiltrated into a bonding agent region infiltrated with silicon. 3 is being implemented.

[0098] Any sequence of layers is possible, in which the reinforcing element 2 between 3D printed bodies 1 embedded (1A, 1C) or a 3D printed body 1 between reinforcing elements 2 embedded (1B). Furthermore, multilayer structures with different layer sequences are possible (1D). Such multilayer structures can be reinforced with rigid or malleable reinforcing elements. 2 realise, particularly when using rigid reinforcing elements 2 the additional bonding agent is applied, so that a firm attachment of the rigid, essentially uncured bonding agent-free, reinforcing element is achieved.2 This is made possible on the body. The outermost layers can optionally be printed on a 3D-printed body. 1 return or reinforcing elements 2 It is a continuous recess in the 3D printed body. 1 enables the connection of two malleable reinforcement elements applied to both sides. 2 and thus an additional form-fitting fixation of the reinforcement elements 2 on the 3D printed body 1 ( Figure 1E ).

[0099] In Figures 2A to G shown are components provided according to the invention, in which the body(s) 1 have recesses into which reinforcing elements 2 are included. The manufacturing process can optionally use rigid or malleable reinforcing elements. 2 This will be done using malleable, uncured resin-containing reinforcing elements. 2 (e.g., resin-fiber compound) can be pressed into the recesses. Rigid reinforcing elements 2are fixed in the recesses by means of an additional bonding agent, whereby the intermediate areas resulting from the bonding agent in Figures 2A to G not indicated. Subsequently, the component provided according to the invention is obtained by carbonization and siliconization.

[0100] Into the component of the Figures 2A For example, fiber rods can be inserted into the component using an adhesive. Figures 2C , D a grid-shaped reinforcing element can be inserted, e.g. a fiber grid.

[0101] In Figure 2E is a cross-section through a multi-layer component consisting of three layers of components made of Figure 2A or 2C shown. A bonding agent can also be used to join the three layers.

[0102] In the component of the Figures 2F , G are the recesses located internally, i.e., all around the body 1 surrounded. A malleable reinforcing element can be inserted into the recesses. 2(e.g. a resin-fiber compound) can be pressed in or a rigid reinforcing element can be used. 2 They can be inserted. For joining with rigid reinforcement elements. 2 The recesses can first be filled with bonding paste and then the reinforcing element inserted. 2 can be inserted. Recesses with a round cross-section are shown, but recesses and reinforcing elements would also work just as well. 2 rectangular or square cross-sections would be conceivable.

[0103] In Figures 3A to D Components provided according to the invention have disc-shaped bodies 1 and ring-shaped reinforcing element 2 shown. The disc-shaped body 1 can be derived from the ring-shaped reinforcing element 2 be surrounded ( Figures 3A, B Alternatively, the reinforcing element can 2 it may also be incorporated into a circumferential groove of the body ( Figures 3C, D The reinforcing element 2can be attached to the disc-shaped body as a rigid ring (e.g. a wound tube made of carban fiber reinforced carbon) using an adhesive paste ( Figures 3A, B ) or introduced into them ( Figures 3C, D ). Alternatively, especially for the production of the component, the Figures 3C , D a malleable reinforcing element (e.g. a resin-fiber compound) is used, which is pressed into the groove. To manufacture the component of the Figures 3A Alternatively, the disc-shaped body can be wrapped with a resin-impregnated fiber strand or a pre-impregnated textile, or a circular knit fabric can be applied. Regardless of how the reinforcing element is attached to the body, components provided according to the invention can be produced by subsequent carbonization and siliconization.

[0104] In Figures 4A , B is a component shown in which an upwardly open body 1with a reinforcement element obtainable from a fiber-containing fill 2 The cavity is filled. Such a component is manufactured by filling the cavity of a 3D-printed body with fiber-reinforced resin. The resin is then compressed using a press or a vacuum bagging process, and more fiber-reinforced resin is added if necessary. Once the entire cavity is filled, the body is fitted with a suitable lid. 4 sealed. A bonding agent can be used for this purpose.

[0105] In Figures 5A and 5B Body 1 is reinforced on all sides with a reinforcing element. 2 overstated Figure 5C Only one side of body 1 has a reinforcing element. 2 Coated. To coat complex surfaces, the surface to be reinforced is coated with a resin-containing reinforcing element. 2The material is covered (e.g., prepreg or fiber-resin compound) and then bonded using a vacuum bag process. The reinforcement element is then applied. 2 This can be done manually, with the help of a robot, or by means of fiber spraying. In the case of van Figure 5C The fabric closure, especially in larger quantities, can also be achieved using a specially shaped press die.

[0106] In the components of the Figures 6A , B the body 1 Undercuts into which the reinforcing element 2 The joint engages in a form-fitting manner, exemplified here by a dovetail joint. Other undercut joints can also be used.

[0107] In Figures 7A , B comprises the 3D printed body 1 canals 6. They can be used to cool the component and reduce weight. This is achieved by using a 3D printing process to manufacture the body. 1Diverse, complex structures can be represented. The introduction of channels. 6 This is fundamentally possible with all components provided according to the invention. The channels can be open on one or both sides.

[0108] In Figures 8A , B, C and D the 3D printed body exhibits silicon-filled segmentation cracks. 5 such cracks can occur when bodies 1 and reinforcement element 2 They exhibit significantly different shrinkage behaviors during heat treatment or significantly different coefficients of thermal expansion. During silicon infiltration, the resulting cracks are filled with silicon, thus contributing to improved heat conduction through the component. The interface areas are also affected. 7 can be filled with silicon, as in Figure 8B indicated. Together with the segmentation cracks, which are also filled with silicon. 5The impression is of a ladder-shaped, silicon-filled structure.

[0109] In Figures 9A and B Components according to the invention are shown, in which 3D printed bodies 1 with a fiber-containing reinforcing element 2 The functional, fiber-reinforced base plate is connected. 3D printing allows for a high degree of design freedom and the production of complex geometries. Such structures are used, for example, as process aids. Using 3D printing, precisely fitting component fixtures, such as for gears, as indicated here, can be produced in which the components can be processed securely and without slippage.

[0110] The graph in Figure 10 Figure 4 shows a stress-strain curve from a bending test on a material whose production is described in embodiment 4. The curve clearly shows pseudoductile fracture behavior and no spontaneous failure.

[0111] In Figure 11is a composite consisting of a reinforcing element comprising short-fiber carbon fibers 2 with a 3D-printed positioned cooling element, which forms a body 1 This represents the short-fiber-reinforced element, which was manufactured by pressing. The cooling element is positioned by a mechanically created hole in the reinforcement element and a corresponding pressed-in pin in the cooling element. Reference symbol list

[0112] 1 Body 2 Fiber-reinforced reinforcement element 3 Silicon-infiltrated bonding agent area 4 Cover 5 Segmentation cracks 6 Channel 7 Interface area Examples of implementation Example 1

[0113] Sandwich construction consisting of a plate-shaped 3D-printed body (100 x 100 x 4 mm) and a reinforcing element in the form of a CFC plate attached to the body. The body was manufactured using a binder jet process from carbon powder and phenolic resin binder and impregnated with phenolic resin before assembly, as described in WO 2017 / 089500 A1. It was then carbonized at 900 °C and tempered at 1650 °C. The CFC plate was produced by laminating four layers of a phenolic resin prepreg (3k carbon fiber), which was then carbonized and densified once with pitch, resulting in a density of 1.2 g / cm³ after a second carbonization.

[0114] The body and reinforcing element were joined using a paste consisting of 50 wt% phenolic resin and 50 wt% SiC powder, with a CFC plate applied to each of the two opposite sides of the 3D-printed body. Curing took place at a maximum temperature of 220°C. The sandwich structure was weighted down with 2 kg across its entire surface.

[0115] After curing, the material was first carbonized at 900 °C and then infiltrated with liquid silicon. At the interfaces with carbon-containing areas, the liquid silicon reacted to form silicon carbide.

[0116] Bending specimens (100 mm x 10 mm x 8.5 mm) were extracted from the resulting plate and tested using a 3-point bending test. The bending curve showed a distinctly pseudoductile behavior, which was achieved by the continuous fibers in the reinforcing element. Example 2

[0117] Sandwich construction consisting of a plate-shaped 3D-printed body (100 x 100 x 2 mm) and a reinforcing element in the form of a phenolic resin prepreg (made of isotropic carbon fiber fleece with a density of 450 g / m²) attached to the body. The body was manufactured using a binder jet process from carbon powder and phenolic resin binder and, prior to joining, impregnated with phenolic resin, carbonized at 900°C, and tempered at 1650°C. A layer of prepreg was applied to each side of the body and pressed together at 7.5 bar and a maximum temperature of 170°C. After curing, the material was first carbonized at 900°C and then infiltrated with liquid silicon. At the interfaces with carbon-containing areas, the liquid silicon reacted to form silicon carbide.

[0118] Bending specimens (100 mm x 10 mm x 3.3 mm) were extracted from the resulting plate and tested using a 3-point bending test. The bending curve showed pseudoductile behavior, which was achieved by the fibers in the reinforcing element. Example 3

[0119] Sandwich structure consisting of a plate-shaped 3D printed body (100x100x10mm) and a reinforcing element in the form of a phenolic resin prepreg (made of isotropic carbon fiber fleece with a density of 450 g / m²) attached to the body. The body was fabricated using a binder jet process from carbon powder and phenolic resin binder and impregnated with phenolic resin before joining. Two layers of prepreg were applied to each side of the body and pressed together at 8 bar and a maximum temperature of 170°C. After curing, the material was first carbonized at 900°C and then infiltrated with liquid silicon. Since the body had not undergone any thermal processing prior to joining, significant shrinkage occurred during the infiltration process. This resulted in segmentation cracks, which were filled in situ with silicon during the infiltration process. A photograph of the cross-section of this sample is shown in Figure 8D to see. Example 4

[0120] A component with a reinforcing element is inserted into recesses in the body. A plate-shaped body with channel-like depressions on the top and bottom was produced from carbon powder using 3D printing. Unlike the component made of... Figures 2A and 2B The plate-shaped body had recesses on both surfaces. This body was impregnated with phenolic resin, carbonized, and graphitized.

[0121] Carbon fibers (50k fibers from SGL Carbon) were impregnated with phenolic resin and cured in a mold at 170°C to serve as reinforcement. The rods were then carbonized.

[0122] The resulting CFC rods were bonded into the recesses of the body using an adhesive paste (SiC, phenolic resin, and alcohol in a mass ratio of 7:2:1), and the entire surface was additionally coated with this paste. The sample was then cured in an oven at 170°C, subsequently carbonized at 900°C, and then infiltrated with liquid silicon.

[0123] Bending specimens (80 mm x 9 mm x 6 mm) were extracted from this plate, each containing exactly one fiber strand on the top and bottom surfaces. These fiber-reinforced specimens exhibited a strongly pseudoductile fracture behavior in the bending curve, in stark contrast to the brittle fracture behavior of the unreinforced bending specimens extracted from the same plate in areas without reinforcement. Furthermore, the fiber-reinforced specimens displayed significant fiber pull-out, which is also a clear indication of increased ductility. An exemplary bending curve of such a fiber-reinforced specimen is shown in Figure 10 depicted. 3-point bending test

[0124] The 3-point bending test was carried out in accordance with ISO 178:2013 with support radius: 3mm, punch radius: 3mm, span: 80 mm, with a test speed of 2 mm / min. Example 5

[0125] A ring-shaped structure made of SiC powder was produced using 3D printing. This structure features a three-dimensional cooling channel structure on one side and a flat back surface on the other. The ring was impregnated with phenolic resin, cured, and carbonized. Such processes are described in WO 2019 / 228974 A1 and WO 2019 / 063833 A1. Subsequently, this heat sink was joined to a carbon short-fiber reinforced carbon substrate, such as that known from EP 1645671, using an adhesive paste. The adhesive paste consisted of a mixture of 50 wt% liquid resol and 50 wt% SiC powder, to which 5 wt% para-toluenesulfonic acid was added as a cold-curing agent. This carbon short fiber reinforced carbon substrate was mixed as described in EP 1645671 by mixing defined cut carbon fiber bundles with a phenolic resin and a graphite powder in an intensive mixer from the company Eirich.The short carbon fibers used in the mixture were protected against subsequent attack by the liquid silicon during the siliconization process in a prior process step. As described in EP 1645671, a 120 cm wide fiber filament tape was first continuously impregnated with a phenolic resin using a film transfer process and thermally and under pressure pre-stabilized by cross-linking the phenolic resin. It was then cut into defined fiber bundle geometries with a length of 12 mm and a width of 1.5 mm using a cutting device. After mixing, the resulting molding compound was compacted and cured in a mold at a temperature of 180 °C to a density of < 1.2 g / cm³. The resulting CFRP molded part was then carbonized at 900 °C under a protective gas atmosphere, resulting in a porous CFRP molded part that was then used for joining with the 3D-printed mold.Finally, this composite was siliconized using liquid siliconization, resulting in a carbon-Si-SiC composite component. This composite component thus features a ductile C / SiC core and additionally incorporates a cooling structure, which can be designed with a high degree of freedom through 3D printing and is made of Si-SiC, resulting in particularly high thermal conductivity. Example 6

[0126] Similar to Example 5, a carbon fiber-reinforced carbon substrate was fitted with 3D-printed cooling elements. First, recesses were drilled into the carbon substrate. Cooling elements made of carbon powder were then 3D-printed, as described in WO 2017 / 089500, and these elements have a small cylinder on their underside. These 3D-printed elements were positioned in the recesses of the substrate, and the composite was subsequently infiltrated with liquid silicon. This positioning method eliminates the need for an adhesive. Optionally, a phenolic resin-based bonding paste can be used to fix the cooling elements in the recesses. Alternatively, the cooling elements can simply be inserted. In this case, using cooling elements with more than one insertion cylinder per element can facilitate fixation.One advantage of the plug-in system is the point-to-point connection of the two components, which reduces thermomechanical stresses during liquid siliconization. Furthermore, the vertically inserted plug-in cylinder improves heat conduction through the component. An example photo of such a composite with a plug-in cooling element is shown in [link / reference]. Figure 11 depicted.

Claims

1. Method for producing a ceramic fiber composite component, comprising the following steps: a) providing a carbon-based and / or ceramic, e.g. silicon carbide-based or boron carbide-based body, which has been produced by means of additive manufacturing, b) treating a reinforcing element and / or the provided body at a temperature of at least 600 °C, preferably at least 800 °C, particularly preferably at least 1400 °C, or at least 1600 °C, before the reinforcing element is attached to the body, c) attaching a fiber-containing reinforcing element to the body, d) connecting the body and reinforcing element by infiltration with silicon or with a silicon-containing compound, and e) if, in step d), the connection is made by infiltration with a silicon-containing compound, a subsequent temperature treatment at more than 400 °C is carried out.

2. Method according to claim 1, wherein the body provided in step a) has been produced by means of binder jetting or paste extrusion.

3. Method of claim 1, wherein the reinforcing element is attached to the body with a bonding agent.

4. Method according to claim 3, wherein the bonding agent is a binding agent which, when heated in an N2-atmosphere, has a material yield of at least 20% by weight.

5. Method according to claim 4, wherein the bonding agent is a paste which takes up at most 10% of the total volume of the fiber composite component present after step c).

6. Method according to claim 1, wherein before or after step c), the body and / or reinforcing element are densified by CVI and / or by infiltration with a carbonizable substance and subsequent carbonization.

7. Method according to claim 1, wherein, prior to step c), the body and / or reinforcing element are infiltrated with silicon or with a silicon-containing compound.