《复合材料 Composites》课程教学资源（学习资料）第五章陶瓷基复合材料_fiber120.pdf_大学文库

Am cermin.Soc,8619l1612-15(2003) journal Application of a Tough Surface Layer to a Fiber-Bonded Composite Yeongseok Kim, Yutaka Kagawa, " and Shijie Zhu Institute of Industrial Science, The University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505, Japan The feasibility of creating tough surface material" using mposition(wt%)of the composite was as follows: Si, 0.56: TI 0.02: C 0.28: 0, 0. 14. It has been reported that the composite has AL, O, fiber/(ZrO2, Al2,)matrix composite was used as the excellent stability at temperatures up to-1800 K in ambient air, rface material of a Si-Ti-C-O-fiber-bonded composite The because a protective oxide layer is formed on the surface at sintering of the matrix(ZrO, and Al2 O3) of the surface temperatures above 1473 K. The composite was cut into 30 composite layer (SCL) and its bonding to the fiber-bonded mm x 60 mm X 5 mm. The surface of the composite was polished composite (FBC) were done simultaneously by vacuum hot up to a 10-um diamond plate finish. The polished composite was pressing. A spherical indentation test demonstrated the advan- oxidized in ambient air at 1573 K for 3 h to form a thin silica tage of the SCL in reducing the damage of the base FBC from (Sio,) layer at the surface. It should be noted that this surface an indenter, because the high fracture resistance of the surface control and oxidation process had no influence on the mechanical composite layer could reduce the stress concentration by the properties of the composite cumulative microfracture process. A sheet of plane woven fabric AlO fiber-ZrO ninicomposite-reinforced Al,O, matrix composite was used as a surface composite layer (hereafter, denoted as SCL). The L. Introduction Tokyo, Japan) was cut into 30 mm X 60 mm. Fiber spacing in the N ON-OXIDE-FIBER-REINFORCED ceramic matrix composites. such as SiC-fiber-reinforced Sic and carbon-fiber-reinforced Sic. bundle(1000 fibers/bundle) was then infiltrated with a ZrO, sol solution(Nissan Chemical Co. Ltd. Tokyo, Japan)and dried in air applications. However, when mechanical damage is induced on at 373 K for 5 h A fine Al2O, particle(Taimei Chemical Co Ltd are known as promising materials for high-temperati structure the surface of these materials, the mechanical performance of the Nagano, Japan) dispersed slurry was prepared and then added in mposites reduces. One way to prevent such mechanical damage poly(vinyl alcohol)(PVA, 0.3 wt%)solution, which can facilitate is to apply a protective coating layer on the surface. However candidates for coating material, such as Al, O, or partially stabi- This bundle unit of Al-O,-fiber-reinforced ZrO, matrix composite lized ZrO,, etc, usually have poor damage tolerance, which leads (hereafter, referred to as AL,O, f-ZrO,) was incorporated in an to a lack of reliability and requires further improvement ALO, matrix. The Al,Of-ZrO, sheet was painted with the Al O3 Recently, oxide-fiber-reinforced oxide matrix composites were slurry. This slurmy-painted material was a"green composite sheet suCe essfully fabricated, and their good damage tolerance was which became(Al, O, f-Zr0, ALO, SCL after sintering.The found as compared with conventionally available monolithic fiber volume fraction of the fabricated SCL was -0.3, the thermal ceramic materials. -7 Thus, it can be expected that the damage expansion coefficients were 5.7 X 10(longitudinal) and 5. X tolerant oxide matrix composite acts as a tough protecting layer for 10-6 K(transversal), and Youngs moduli were 70 (longitudi a non-oxide composite from environmental attack. However, to the nal)and 34 GPa(transversal). Details of the fabrication process best of the authors'knowledge, no report has yet been published the green composite sheet were reported elsewhere on the application of oxide-fiber-reinforced oxide matrix compos composite specimen is shown in Fig. I. A completely dried green ceramic matrix composites. The major purpose of the present composite sheet was placed on the oxidized composite and put into a paper is to demonstrate the potential of Al2O, fiber/(Z:O2, Algo, the green composite sheet and the bonding between the SCL and the FBC were conducted at 1473 K under vacuum (-55X 10 Pa) for 3 h under an applied pressure of -10 MPa. After this process, the l. Experimental Procedure bonded material was cooled to room temperature under vacuum with natural cooling rate of the furnace. The polished transverse cross Si-Ti-C-O-fiber-bonded composite(hereafter, denoted as sections of the bonded specimen were observed by an optical BC)material (Tyranno-hex, Ube Industries Co. Ltd, Yamagu microscope and a scanning electron microscope chi, Japan)was used as a base material. The material was Toexamine the potential of the SCL as a barrier against extermal fabricated by hot-pressing woven fabric sheets of preoxidized mechanical damages, a sphere indentation test was performed Si-Ti- C-O fibers. The nominal fiber volume fraction of th As-bonded material was cut into a specimen with dimensions of 30 composite was.9. The thermal expansion coefficient was 3. 1x mm X 30 mm X 5 mm. A steel ball (Youngs modulus: 210 GPa) K-l and Young's modulus was 115 GPa. The chemical of 20-mm diameter was used as an indenter. A compressive load was applied to the specimen using a screw-driven test machine Model 4204, Instron Corp, Danvers, MA). The test was done at room temperature(297 K) in air with a crosshead displacement 4. S. Jacobson--contributing editor rate of o I mm/min During the indentation test, acoustic emission (AE) monitoring was performed to affix directly on the SCL. To examine the effect of the SCL, a FBC specimen without an SCL was also tested. Its shape and dimensions were identical to those of Manuscript No. 187208, Received January 14, 2002: approved March 10, 2003. the specimen with the SCL. The surface of the specimen was Corresponding author (kagawa(g iis, u-tokyo ae jp) polished up to a I-um diamond paste finish

September 2003 Communications of the American Ceramic Society (a-1)Preparation of(Al2O3f-Zro2)Al2O3 eported, 0, It is clear that se of hot pressing allows the green composite sheet sintering of the SCL and its bonding to the FBC. It has been identified by the X-ray diffraction that the bonding is due to the chemical reaction between the thin amorphous SiO, layer of the FBC and the ScI Figure 3(a) is a typical polished section of the bonded material after an indentation load of -27 kN that is about 80% of the (a-2)Formation of oxide layer dentation load at the fracture, Arrows indicate the damaged portion of the SCL. Two kinds of damage are observed: (i) Sio, layer compressive impression at the contact region and (ii) fracture of the surface composite layer at the edge of the impression.The compressive damage in the SCL is due to the compressive force perpendicular to this SCL on the contact zone. The fiber fracture occurs at the contact edge between the spherical indenter and the SCL, Details of the fiber fracture behavior are shown in Fig. 3(b). The photograph reveals that the Al,O, fiber is removed by the (b)Vacuum hot-press(Sintering+ Bonding) indentation, although the Al,O, matrix layer still adheres to the surface of the FBC Figure 4 shows a typical indentation load (P)-displacement(8) Green composite curve of the FBC without (a) and with(b)an SCL For the specimen sheet(single layer) without the SCL the initial damage occurs when the indentation load reaches-4 kN(Po), indicated by the initial load drop on the curve and AE signals at the same time. Visible damage is clearly identified on the specimen surface after louding to -4 kN. After the load drop. the load increases again linearly with an increase of crosshead er Bonded displacement up to a maximum load(P). At the maximum load. the Composit FBC specimen is catastrophically broken into several pieces.The slope in the FBC specimen, P/o is -42 kN/mm. In contrast, the load-displacement curve of the SCL-bonded composite shows two difterent regimes; i. e, the curve is divided into two characteristic (c) Bonded material stages with two different slopes. At stage I, the load increases linearly up to-26kN, followed by a small load drop. Then, the load increases again with the increase in the crosshead displacement(stage II).The Surface composite slope at stage I(P/0-25 KN/mm) is lower than that at stage II(P/8- ay 54 KN/mm). Similar load-displacement relations were obtained fro er Bonded e tested specimens. The load-displacement curve of the SCL-bonded composite indicates that the SCL acts like a ductile deformable material during stage I. It is clear that microfractures Base material occur on the SCL during this stage(Fig. 4(b)), judged from the increase of the AE event above the load of-20 kN. When the applied Fig 1. Schematic drawing of bonding procedure of an SCL-bonded FBC. load reaches PI, the SCL is already completely fractured (loses its function as a protective coating)and then the load directly transfers to the substrate through the compressed SCL, since the SCL is com Il. Results and Discussion pressed and thus apparent compliance increases. It is clear that the SCL can protect the surface from damages because the load-drop by igure 2 shows a typical example of the polished cross section cracking the FBC (P,- 26 kN)in SCL-bonded composite is much of the bonded material. The -300-um-thick SCL is well-bonded higher than that (Po -4 kN)in the composite without SCL, and there to the base FBC. although some pores are observed between them. is no remarkable cracking behavior of the base FBC before P, in the The microstructure of the SCL is similar to that previously SCL-bonded composite. Surface composite layer(300um (A2O3F-Zro2)Al2 O3 Interface Base material SiTiCO FBC 100 Fig. 2. Typical example of the polished cross section of an SCL-bonded FBC

《复合材料 Composites》课程教学资源（学习资料）第五章 陶瓷基复合材料_fiber120

《复合材料 Composites》课程教学资源（学习资料）第五章陶瓷基复合材料_fiber120