Method for producing a composite material component

Abstract

The invention relates to a method for producing a composite material component, comprising the following steps: providing a negative mold, fine machining of the negative mold, applying at least one functional layer by means of thermal spraying to the negative mold, applying at least one fiber-reinforced plastic layer with a curable matrix material, curing the matrix material, and detaching the composite material component from the negative mold.

Claims

1. A method for producing a composite material component comprising the following steps: (a) providing a negative form; (b) finish treating said negative form at said surface thereof so that said surface of said negative form has a surface characteristic Sa≤5 μm and a surface roughness characteristic of Sz≤80 μm; (b1) cooling said negative form; (c) applying at least one functional layer by means of thermal spraying onto said negative form; (c1) applying an adhesion agent layer consisting of a metal or metal alloy; (d) applying at least one fiber-reinforced plastic layer including a hardenable matrix material; (e) hardening said matrix material; and (f) releasing said composite material component, comprising the at least one functional layer and the at least one fiber-reinforced plastic layer, from said negative form to thereby obtain the composite material component; wherein said step (b) is performed after said step (a) and before said step (c); wherein step (c1) is performed after said step (c) and before step (d); wherein said negative form is made of a material which is selected from the group consisting of metals, metal alloys, ceramics, salts and glasses; and wherein said material of said negative form and said functional layer are selected so that a difference (Δα) of said coefficients of thermal expansion between said material of said negative form and said functional layer is smaller than 1.Math.10.sup.−4/K.

2. The method of claim 1, wherein said finish treatment within step (b) is performed so that said surface of said negative form has a surface characteristic Sa≤3.5 μm, and a surface roughness characteristic of Sz≤50 μm.

3. The method of claim 1, wherein said material of said negative form and said functional layer is selected so that said difference (Δα) of said coefficients of thermal expansion between said material of said negative form and said functional layer is larger than 1.Math.10.sup.−6/K.

4. The method of claim 3, wherein said material of said negative form and said functional layer is selected so that said difference (Δα) of said coefficients of thermal expansion between said material of said negative form and said functional layer is larger than 10.Math.10.sup.−6/K.

5. The method of claim 1, wherein said negative form before applying at least one functional layer by means of thermal spraying is pre-heated.

6. The method of claim 1, wherein said negative form before applying at least one functional layer by means of thermal spraying is pre-heated to a temperature of at least 100° C.

7. The method of claim 1, wherein said adhesion agent layer consists of a metal selected from the group consisting of aluminum, nickel, steel, zinc, titanium, molybdenum, chromium, cobalt, silicon, alloys, and mixtures thereof.

8. The method of claim 1, wherein said functional layer is applied with a thickness of 20 to 1000 μm.

9. The method of claim 1, wherein said functional layer applied in step (c) is selected from the group consisting of a ceramic layer, a cermet layer, and a metal layer.

10. The method of claim 1, wherein said fiber-reinforced plastic material comprises fibers that are selected from the group consisting of organic fibers, inorganic fibers, metallic fibers, natural fibers, and mixtures thereof.

11. The method of claim 1, wherein said fibers are soaked within a hardenable matrix material.

12. The method of claim 1, wherein said matrix material is selected from the group consisting of resins, polymers, and mixtures thereof.

13. The method of claim 1, wherein said fiber-reinforced plastic layer is applied with a thickness of ≥500 μm.

14. A method for producing a composite material component comprising the following steps: (a) providing a negative form; (b) finish treating said negative form at the surface thereof so that said surface of said negative form has a surface characteristic Sa≤5 μm and a surface roughness characteristic of Sz≤80 μm; (c) applying at least one functional layer by means of thermal spraying onto said negative form; (c1) applying an adhesion agent layer consisting of a metal or metal alloy; (d) applying at least one fiber-reinforced plastic layer including a hardenable matrix material; (e) hardening of said matrix material; and (f) releasing said composite material component, comprising the at least one functional layer and the at least one fiber-reinforced plastic layer, from said negative form to thereby obtain the composite material component, wherein said step (b) is performed after said step (a) and before said step (c); wherein step (c1) is performed after step (c) and before step (d); wherein said negative form is made of a material which is selected from the group consisting of metals, metal alloys, ceramics, salts and glasses; and wherein said material of said negative form and said functional layer are selected so that a difference (Δα) of said coefficients of thermal expansion between said material of said negative form and said functional layer is smaller than 1.Math.10.sup.−4/K.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the invention can be taken from the subsequent description of preferred embodiments with reference to the drawings. In the drawings show:

(2) FIG. 1 the fundamental process procedure for the production of composite material components according to the method of the invention;

(3) FIG. 2 two composite material components produced according to the invention;

(4) FIG. 3 a fiber winding apparatus;

(5) FIG. 4 a light microscopic picture of a cross section of a fiber-reinforced coated plastic manufactured according to the prior art; and

(6) FIG. 5 am SEM picture of a cross section of a composite material component produced according to the invention.

(7) The fundamental steps of the method according to the invention for producing composite material component are shown schematically in FIG. 1. It is a six-stage method (S10, S12, S14, S16, S18 and S21). This method can be further augmented by additional method steps (S20). The composite material component may be a fiber-reinforced plastic which is provided with a coating, the functional layer.

(8) In the first step S10 a negative form is provided. This may be a rotationally symmetric shape. Other shapes, such as for instance polyhedrons having several sides, are also possible. In a further preferred configuration the negative form is a conical form. These forms facilitate the later detachment of the negative form in the step S18. The negative form determines the shape of the final composite material component to a large extent. If the negative form is for instance a cylinder, then a composite material component in the shape of a tube can be produced. Flat forms are also possible according to the invention.

(9) The surface of the negative form determines the surface structure and the roughness of the functional layer of the composite material component, since this form is mirrored. A pattern or texture is thus possible.

(10) In an additional step, which is performed before the thermal spray coating (S12), the negative form is finish-processed, see step S21 (dashed box). Herein the form is for instance polished, grinded or lapped. This treatment facilitates the detachment in step S18. In addition in this way a composite material component having a particularly smooth functional surface (net-shape) can be produced.

(11) The materials from which the negative form can be made are preferably metals or metal alloys. These metals allow a simple and cost effective preparation of the negative forms. The materials also have the advantage that the negative forms can be reused many times. The material of the negative form is tailored to the material of the functional layer, in particular by selecting Δα. Preferably for instance an aluminum alloy with an α of about 25.Math.10.sup.−6/K can be used for the negative form, for instance in combination with an Al.sub.2O.sub.3 coating having an α of about 7 to 9.Math.10.sup.−6/K, leading to a Δα of >15.Math.10.sup.−6/K.

(12) When using a steel core (stainless steel) with a functional layer of ZrO.sub.2 a Δα of >2.Math.10.sup.−6/K results. Using a steel core with a functional layer of Al.sub.2O.sub.3 leads to a Δα of >5.Math.10.sup.−6/K. As far as not indicated differently, the coefficients of thermal expansion α are to be understood in the range of 20° C. to 300° C.

(13) The step S10 is followed by the finish treatment (step S21), e.g. by grinding or polishing, to obtain a smooth surface. Herein an Sa-value of <3.5 μm and a Sz-value of <50 μm is set.

(14) The step S21 is followed by the application of at least one functional layer by means of thermal spraying onto the negative form (step 12). The functional layer preferably is a ceramic layer and/or a cermet layer.

(15) The functional layer is a coating that protects the layer/layers in the final composite material component against outer influences and provides particular characteristics thereto. For instance the functional layer serves the purpose of corrosion protection, wear protection, etc.

(16) According to an alternative method between the steps S21 and S14 an optional method step S20 is introduced. Herein an adhesion agent layer is applied, preferably by means of thermal spraying. The adhesion agent layer serves to hold together the functional layer and the fiber-reinforced plastic layer as far as possible by material connection using a highly adhesive binding. Depending on the material of the functional layer and the fiber-reinforced plastic layer this step may be dispensed with. In particular, when the functional layer adheres to the fiber-reinforced plastic layer strongly. By the method according to the invention a further improved adhesion can be reached by the penetrating of the matrix material into the outer regions of the functional layer.

(17) The adhesion agent layer consists of metals or a metal alloy, in particular of aluminum, nickel, steel, zinc, titanium, molybdenum, chromium, cobalt, silicon, alloys and/or mixtures thereof.

(18) It will be understood that several functional layers, or adhesion agent layers, respectively, can be applied one over the other.

(19) The functional layer and possibly the adhesion agent layer are applied by means of thermal spraying. Herein the material to be applied is molten within or out of a spraying device and is thrown onto the prepared surface. For instance melting bath spraying, light arc spraying, plasma spraying, flame spraying, high velocity flame spraying, cold gas spraying, wire flame spraying, powder flame spraying, detonation spraying, suspension spraying, precursor spraying, or laser spraying can be applied.

(20) The layer thickness of the thermally sprayed layers may be between 20 to 1000 μm, preferably between 50 to 500 μm, in particular preferred between 100 up to 200 μm. By means of the thermal spraying particularly smooth and thin layers can be applied.

(21) After applying at least layer onto the negative form in the following method step S14 at least one fiber-reinforced plastic layer is applied. The application of the fiber-reinforced plastic layer can be performed onto the functional layer or possibly onto the adhesion agent layer.

(22) The fibers of the fiber-reinforced plastic layer may be organic fibers, inorganic fibers, metallic fibers, natural fibers and/or mixtures thereof, while the matrix material preferably is a resin. In addition, the fibers may also be processed fibers, i.e. such fibers that are woven, non-crimped, stitched or plaited. In addition the fibers may also be semi-finished products, based on fibers or yarns of fibers, respectively, but also short fibers.

(23) The fibers may be applied onto the functional layer, or the adhesion agent layer, respectively, by hand-laminating, fiber spraying, pressing, pultrusion methods, injection molding, radial winding, cross winding, polar winding, resin injection methods or autoclave methods. In an alternative design the fibers may be soaked within a hardenable matrix material. This allows for a simultaneous application of fibers and matrix material. Alternatively the last applied layer (adhesion agent layer or functional layer) can be soaked with a hardenable matrix material. Thereafter the fibers can be applied, e.g. by winding, possibly followed by a further soaking step. Depending on the fiber type and matrix material one of these soaking methods may be advantageous.

(24) Due to the liquid aggregate state of the matrix material the latter can penetrate into layers thereunder. Herein an additional micro-clamping between the layers results so that an additional adhesion is reached.

(25) In addition by the application method that is used in step S14 the tension ratio between the individual layers can be determined in a preferred way. When applying the fiber-reinforced plastic layer, a pressure tension can be generated (for instance by winding the fiber layer with a certain tensile stress), which acts from the outside onto the inner, thermally sprayed functional layer. In this way the functional layer that is sensitive to tensile stress is biased with pressure so that in total a significantly increased strength of the final composite material component results. The bias generated during winding during the subsequent hardening of the matrix material is secured within the fiber-reinforced plastic layer, and is thus kept permanently.

(26) The fiber-reinforced plastic layer may have a layer thickness von ≥500 μm, preferably of ≥700 μm, in particular preferred of about ≥900 μm, wherein the thickness preferably is 5 cm at the most. Depending on the application purpose of the composite material component a particularly thin layer may be advantageous.

(27) After applying at least two layers onto the negative form, the method step S16 is carried out. Herein the matrix material is hardened. The hardening may be facilitated for instance by increased temperatures, by special additions into the matrix material or by increased pressures onto the fiber-reinforced plastic layer. By the hardening of the matrix material a micro-clamping within the layers into which the matrix material could penetrate, results. In addition the fibers are fixed within the matrix material.

(28) In the final method step S18 the composite material component is released from the negative form to thereby obtain the final composite material component. For instance the release may be facilitated by means of cooling the negative form.

(29) During release it should be ensured that the functional layer is fully detached from the negative form. Apart from the cooling this is also influenced by the selection of the material and by the surface treatment of the negative form. In addition by setting the surface roughness, the detachment can in addition be facilitated; particularly smooth structures are preferred herein.

EXAMPLES

(30) FIG. 2 shows two composite material components 10 and 12 there were produced according to the method of the invention. Herein two tubes 10 and 12 having an inner diameter of 100 mm and an outer diameter of 103.2 mm, or 104 mm, respectively, are provided. The inner diameter of the tubes herein corresponds to the outer diameter of the negative form. The outer layer of the tubes forms the fiber-reinforced plastic layer 14. Commercial carbon fibers (Toray T700SC 12K 50C of the company Toray, Neu-Isenburg, Germany) were used as fibers, and an epoxy resin (Epoxidresin L+Hardener EPH 161 Poxy Systems of the company R&G, Waldenbuch, Germany) was used as matrix material. The thermally sprayed functional layer on the one hand consisted of aluminum oxide 16 (bright inner coating) (Al.sub.2O.sub.3 99.7%, molten powder, −20+5 μm, of the company Ceram GmbH Ingenieurkeramik, Albbruck, Germany), and on the other hand of titanium oxide 18 (dark inner coating) (TiO.sub.2 99%, molten powder, −38+15 μm, of the company Ceram GmbH lngenieurkeramik, Albbruck, Germany). Both tubes 10, 12 had a thermally sprayed adhesion agent layer (not visible). In both cases aluminum (aluminum 99%, powder, spray aeriated, −75+45 μm, Metco 54NS-1 of the company Oerlikon Management AG, Pfäffikon, Switzerland) was used.

(31) In both cases tubes of 6060 aluminum alloy were used as negative form. These were 400 mm long, having an outer diameter of 100 mm and a wall thickness of 3 mm. The core surface of the negative form before the application of the functional layer was ground (using P800, P1200, and P2000 grinding paper) and polished (universal polishing paste of the company R&G, Waldenbuch, Germany).

(32) The application of the functional layer as well of the adhesion agent layer onto the negative form was done by means of atmospheric plasma spraying (APS). Herein an APS burner F6 of the company GTV Verschleißschutz GmbH, Luckenbach, Germany was used. The selected parameters are summarized in the following table 1.

(33) TABLE-US-00001 TABLE 1 Functional layer Functional layer Adhesion agent (Al.sub.2O.sub.3); molten (TiO.sub.2); molten layer (Al); gas powder powder aeriated powder Plasma gases: Ar 44 L/min 46 L/min 45 L/min H.sub.2 12 L/min 8 L/min 6 L/min Current 600 A 500 A 470 A strength (I) Powder transportation: Ar (carrier gas) 6 L/min 6 L/min 6 L/min rotation of 1.8 rpm 2.0 rpm 1.2 rpm turntable (rpm)

(34) The application of the fiber-reinforced plastic layer was performed by means of a fiber winding method (cf. FIG. 3). Herein two fiber layers were applied unidirectionally, and two fiber layers had an angle of 80°. The fiber pre-tension was 6 N, the winding breadth corresponded to the tube length of about 180 mm.

(35) After applying the layers the resin was hardened for 24 h at room temperature and for further 16 hours at 65° C.

(36) The release of the final composite material from the negative form was facilitated by means of cooling. To this end the aluminum core of the negative form was cooled from the inside using two CO.sub.2 lances (TSF nozzles, Linspray, of the company Linde, Pullach, Germany) for 5 min. During the CO.sub.2 cooling a dry ice-gas mixture was sprayed onto the component at a temperature of about −73° C. An ejection/retraction of the final composite material was facilitated by the strong contraction of the aluminum core.

(37) The layer thicknesses of the individual layers of the two tubes 10 and 12 are summarized in the subsequent table 2.

(38) TABLE-US-00002 TABLE 2 Bright inner coating Dark inner coating Functional layer 260 μm (Al.sub.2O.sub.3) 160 μm (TiO.sub.2) Adhesion agent layer 140 μm (Al) 140 μm (Al) Fiber-reinforced plastic 1.6 mm 1.3 mm layer

(39) FIG. 3 shows a fiber winding method 40 which was used during the production of the composite materials according to FIG. 2. This method allows for an application of a fiber layer 42, wherein the fibers 44 initially were drawn through a bath 46 of liquid matrix material 48. Herein the fibers 44 are soaked. The matrix material 48 may be a resin. For this method cylindrical, conical, spherical or any other shape of the negative form 50 is suitable.

(40) During the method the negative form 50 is rotated, so that the fiber 44 can be wound around the coated negative form 50 and can be simultaneously drawn from a supply coil 52. The fiber 44 is under pre-tension and is guided through an impregnating unit, the bath 46 that is filled with matrix material 48. The location of the soaked fibers 56 on the coated negative form 50 is control by means of a guiding unit 54.

(41) FIG. 4 shows a picture taken by light microscopy of a cross section of a commercial fiber-reinforced plastic material which was coated using the conventional method. This consists of two layers: one fiber-reinforced plastic layer 20 and a metallic adhesion agent layer 22 made of aluminum (the application of a further layer was dispensed with). The plastic was produced according to the conventional method. This method contained the method steps: 1. providing a fiber-reinforced plastic material; 2. surface activating by means of sand blasting; and 3. applying an adhesion agent layer by means of thermal spraying.

(42) The damages 24 and 26 within the fiber-reinforced plastic layer can clearly be seen. These damages were generated by the surface activation by means of sandblasting and by the application of the adhesion agent layer. Apart from the carbon fiber breakouts 24 also disintegrations 26 in the region of the polymer matrix can be seen. The carbon fiber breakouts 24 result from the surface activation. Herein the surface is roughened and thus increased. The roughening has the purpose to improve the mechanical anchoring of the coating. However, as shown here, damages of the fiber-reinforced plastic layer result. The disintegrations 26 within the polymer matrix primarily result from the coating method. During thermal spraying particularly high temperatures are used. During impact of the metallic adhesion agent layer onto the matrix layer disintegration reactions occur.

(43) FIG. 5 shows an SEM photo of a cross section of a composite material according to the invention. This comprises three layers: one fiber-reinforced plastic layer 28, one adhesion agent layer 30, and a functional layer 32.

(44) The preparation of this composite material (tube) was done almost in analogy to the method described with reference to FIG. 2, wherein departing therefrom as a functional layer a ceramic layer of Al.sub.2O.sub.3/TiO.sub.2 (97%/3%) was applied by means of APS. The inner diameter of the tube was 100 mm, and the outer diameter 101.4 mm. The outer layer of the tube forms the fiber-reinforced plastic layer 28. As fibers 34 commercial carbon fibers (Toray T700SC 12K 50C of the company Toray, Neu-Isenburg, Germany) were utilized, and as a matrix material an epoxy resin (epoxy resin L+hardnener EPH 161 Poxy Systems of the company R&G, Waldenbuch, Germany) was used. As a material for the functional layer aluminum oxide/titanium oxide 32 (Al.sub.2O.sub.3/TiO.sub.2 97%/3% molten powder, −40+10 μm, of the company GTV Implex GmbH, Luckenbach, Germany) was used. As an adhesion agent layer 30 aluminum was used (aluminum 99%, gas aeriated powder, −75+45 μm, Metco 54NS-1 of the company Oerlikon Management AG, Pfäffikon, Switzerland).

(45) As a negative form the tube as mentioned above was used.

(46) The application of the functional layer as well as of the adhesion agent layer onto the negative form was performed by means of atmospheric plasma spraying (APS). Herein an APS burner F6 of the company GTV Verschleißschutz GmbH, Luckenbach, Germany was used. The parameters that were used are summarized in the following table 3.

(47) TABLE-US-00003 TABLE 3 Functional Adhesion layer (Al.sub.2O.sub.3/TiO.sub.2); agent layer (Al): molten powder gas-aeriated powder Plasma gases: Ar 44 L/min 45 L/min H.sub.2 12 L/min 6 L/min Current strength (I) 600 A 470 A Powder transportation: Ar (carrier gas) 6 L/min 6 L/min Rotation of turntable (rpm) 1.8 rpm 1.2 rpm

(48) The application of the fiber-reinforced plastic layer was performed by means of a fiber winding method (see FIG. 3). Herein two fiber layers were applied unidirectionally and two fibers has an angle of 80°. The filament pre-tension results from the application onto the fiber coil and by the respective braking force. The braking force was 6 N, the winding breadth corresponded to the tube length of about 180 mm.

(49) After applying the layers the resin was hardened for 24 h at room temperature and for further 16 h at 65° C.

(50) The detachment of the final composite material from the negative form (cylindrical, without any conical shape) was facilitated by means of cooling. To this end the aluminum core of the negative form was cooled from the inside for 5 min with two CO2 lances (TSF nozzles, Linspray of the company Linde, Pullach, Germany). The layer thicknesses of the individual layers are summarized within the subsequent table 4.

(51) TABLE-US-00004 TABLE 4 Functional layer 200 μm (Al.sub.2O.sub.3/TiO.sub.2) Adhesion agent layer 180 μm (Al) Fiber-reinforced plastic layer 0.9 mm

(52) In the SEM photograph of FIG. 5 no damages between the individual layers can be seen, by contrast to FIG. 4. Instead from FIG. 5 it can be taken that the polymer matrix 36 according to the method according to the invention is infiltrated into the layer thereunder (adhesion agent layer 40), and thus an additional micro-clamping 38 of the individual layers results.

(53) To investigate the particular characteristics of the composite material component (according to example of FIG. 5) several measurements were performed. Herein inter alia it was investigated, which surface roughness of the negative form is particularly preferred and which adhesion strength can be produced by the method according to the invention. The production of the composite materials was performed as described in the example with respect to FIG. 5, as far as not indicated differently.

(54) Characterization

(55) 1. Determination of Surface Characteristics

(56) First it was investigated which surface roughness of the negative form is particularly preferred. To this end a negative form made of stainless steel and another five negative forms made of aluminum were produced and finish treated in different ways. The negative form in all cases had an outer diameter of 100 mm. The surfaces of the individual negative forms were measured before producing a tube coated on the inside (according to example of FIG. 5) using white light interferometry. The measurement was performed using the measurement device “Contour GT-K” of the company Bruker, Billerica, USA. Using the assigned software “Vision 64” the surface characteristics Sa and Sz were computed. The following measurements were obtained according to table 5:

(57) TABLE-US-00005 TABLE 5 Finish treatment S.sub.a [μm] S.sub.z [μm] Stainless steel core, untreated 4.68 38.11 Aluminum core, blasted and polished with 1200 2.92 37.62 Aluminum core, polished and blasted 1.43 40.83 Aluminum core, machine-polished, re-used 0.59 9.36 Aluminum core, machine-polished 0.63 5.12 Aluminum core, machine-polished and hand-polished 0.57 4.46

(58) After the individual composite material component had been produced according to the method described above, it was found that the composite material components can be released from the negative form particularly well, if the surface roughness of the negative form has surface characteristics of S.sub.a≤3.5 μm and S.sub.z≤50 μm.

(59) 2. Adhesion Tensile Strength

(60) For the next measurements again a tube coated on the inside was produced. The production was done according to FIG. 5. In the experiment the adhesion tensile strength of the individual layers was investigated by means of a stamp retraction investigation. The method was performed along the lines of DIN EN 582. To this end the functional layer (Al.sub.2O.sub.3/TiO.sub.2; 97%/3%) of the composite material component a stamp glued-on (so-called test stamp) was withdrawn evenly and slowly using a tension test machine perpendicularly to the surface until breakaway (rupture) occurred.

(61) As the retraction device the model “PAT (Precision Adhesion Testing Equipment) AT101E” of the company DFD Instruments Woking, United Kingdom, was utilized. As a stamp diameter Ø8.16 mm was used, wherein the face surface was built convexly onto Ø100 mm, to rest at the tube bending matingly. As an adhesive “Loctite EA 9466” was used.

(62) In the experiment adhesive strengths >17 MPa were measured. Such values are not known from comparable, conventional composite materials having thermally sprayed functional layers. With conventional composite materials only maximum adhesive strengths of 13 MPa were measured, however, usually <10 MPa.

(63) In the experiment it was also found that the ruptures almost exclusively were located within the ceramic layer (Al.sub.2O.sub.3/TiO.sub.2); thus within the outer functional layer. Thus only cohesion ruptures within the outermost layer occur. However, the other layers usually remain intact. Using the method according to the invention thus a particularly good adhesion between the fiber-reinforced plastic and the adhesion agent layer is reached.