《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_porous-sIC-1.pdf_大学文库

Availableonlineatwww.sciencedirect.com SCIENCE IRECTI SOLID STATE CHEMISTRY ELSEVIER Journal of Solid State Chemistry 177(2004)487-492 http://elsevier.com/locate/jssc Preparation, microstructure and mechanical properties of SiC-Sic and B4c-B4c laminates S. Tariolle, C. Reynaud, F. Thevenot, T. Chartier, and J. L. Besson Laboratoire Ceramiques Speciales, Ecole Nationale Superieure des Mines de saint-Etienne, 158 Cours Fauriel, F-42023 Saint-Etienne Cedex 2, france b SPCTS. Ecole Nationale Superieure de Ceramique Industrielle, 47-73 avenue Albert Thomas, F-87065 Limoges Cedex, france mber 2002: accepted 27 February 2003 Abstract Silicon carbide and boron carbide are high hardness materials with a low density but, like most ceramics, with a low toughness, that limits their use in various applications. One approach to reinforce ceramic materials consists in using crack deflection by weakening the interfaces in laminar materials In our study, ceramic layers of different compositions were prepared by tape castin spray for B.C. After debinding, SIC(Al2O3, Y2O3 additions) and BC(C addition) were pressureless sintered. For evaluation of the sintered parts, firstly the macrostructure and microstructure were characterized. Then, mechanical properties of multi-layered materials, obtained by stacking dense and porous layers that should contain enough porosity to initiate crack deflection, according to the models. were evaluated C 2003 Elsevier Inc. All rights reserved Keywords: Boron carbide; Silicon carbide: Laminar materials; Tape casting: Rupture: Crack deflection 1. Introduction porous ceramic materials. It is well-known that the interface crack deflection is influenced by the fracture a way to reinforce ceramics, often characterized by energy and by Youngs modulus of materials constitut- their low toughness that induces catastrophic rupture of ing each side of the interface [6,7]. These two properties the materials, is to use laminar materials. Thus, are dependent on the porosity functionally graded materials were chosen to improve He and Hutchinson [8] established, in the case of a fracture toughness in non-oxide ceramics. The use of weak graphite interface in SiC material, that the ratio mechanical properties of ceramic materials Improve between fracture energies of the weak interface G and of weak interfaces or interlayers allows he strong layer Gs must fulfil the following criterion to interface can be made by the incorporation of graphite allow the crack to deflect at this interface [1], boron nitride [2] or oxide ceramics(LaPO4 or YPO4) [3]. Another way to reinforce ceramic materials is to G/G≤0.57 introduce porous ceramic interlayers. Thus, alternate For dense-porous laminates, Clegg et al. [4,5 dense-porous alumina 14] and alternate dense-porous expressed this criterion considering that the interfac SiC (solid phase sintering) were made [5]. In these energy G is replaced by the ligament energy Glig materials, crack deflection occurred at the interface (ligament of ceramic material between pores in which was in porous and dense layers and the fracture energy the crack propagates) ased Clegg et al. [4, 5] proposed an energetic criterion to Glig/Gs$0.57 explain crack deflection mechanism in alternate dense- Therefore, Eq (2)can be expressed in relation with porosity Corresponding author. Fax: + 33-4-77-42-00-00 E-mail address. tariolle(@ emse. fr(S. Tariolle) Gp/Ga(1-p)≤0.57 0022-4596/Ssee front matter C 2003 Elsevier Inc. All rights reserved. doi:10.1016/jc.2003.02007

Journal of Solid State Chemistry 177 (2004) 487–492 Preparation, microstructure and mechanical properties of SiC–SiC and B4C–B4C laminates S. Tariolle,a, C. Reynaud,a F. The´venot,a T. Chartier,b and J.L. Bessonb a Laboratoire Ce´ramiques Spe´ciales, Ecole Nationale Supe´rieure des Mines de Saint-Etienne, 158 Cours Fauriel, F-42023 Saint-Etienne Cedex 2, France bSPCTS, Ecole Nationale Supe´rieure de Ce´ramique Industrielle, 47-73 avenue Albert Thomas, F-87065 Limoges Cedex, France Received 24 September 2002; accepted 27 February 2003 Abstract Silicon carbide and boron carbide are high hardness materials with a low density but, like most ceramics, with a low toughness, that limits their use in various applications. One approach to reinforce ceramic materials consists in using crack deflection by weakening the interfaces in laminar materials. In our study, ceramic layers of different compositions were prepared by tape casting and stacked in predefined sequences. Different weak layers were tested: porous layers made with different pore forming agents for SiC; porous layers made with pore forming agent or by varying the quantity of sintering aid and weak interfaces made with graphite spray for B4C. After debinding, SiC (Al2O3, Y2O3 additions) and B4C (C addition) were pressureless sintered. For evaluation of the sintered parts, firstly the macrostructure and microstructure were characterized. Then, mechanical properties of multi-layered materials, obtained by stacking dense and porous layers that should contain enough porosity to initiate crack deflection, according to the models, were evaluated. r 2003 Elsevier Inc. All rights reserved. Keywords: Boron carbide; Silicon carbide; Laminar materials; Tape casting; Rupture; Crack deflection 1. Introduction A way to reinforce ceramics, often characterized by their low toughness that induces catastrophic rupture of the materials, is to use laminar materials. Thus, functionally graded materials were chosen to improve fracture toughness in non-oxide ceramics. The use of weak interfaces or interlayers allows to improve mechanical properties of ceramic materials. The weak interface can be made by the incorporation of graphite [1], boron nitride [2] or oxide ceramics (LaPO4 or YPO4) [3]. Another way to reinforce ceramic materials is to introduce porous ceramic interlayers. Thus, alternate dense–porous alumina [4] and alternate dense–porous SiC (solid phase sintering) were made [5]. In these materials, crack deflection occurred at the interface between porous and dense layers and the fracture energy was increased. Clegg et al. [4,5] proposed an energeticcriterion to explain crack deflection mechanism in alternate dense– porous ceramic materials. It is well-known that the interface crack deflection is influenced by the fracture energy and by Young’s modulus of materials constituting each side of the interface [6,7]. These two properties are dependent on the porosity. He and Hutchinson [8] established, in the case of a weak graphite interface in SiC material, that the ratio between fracture energies of the weak interface Gi and of the strong layer Gs must fulfil the following criterion to allow the crack to deflect at this interface: Gi=Gsp0:57: ð1Þ For dense–porous laminates, Clegg et al. [4,5] expressed this criterion considering that the interface energy Gi is replaced by the ligament energy Glig (ligament of ceramic material between pores in which the crack propagates): Glig=Gsp0:57: ð2Þ Therefore, Eq. (2) can be expressed in relation with porosity p: Gp=ðGdð1 pÞÞp0:57; ð3Þ ARTICLE IN PRESS Corresponding author. Fax: +33-4-77-42-00-00. E-mail address: tariolle@emse.fr (S. Tariolle). 0022-4596/$ - see front matter r 2003 Elsevier Inc. All rights reserved. doi:10.1016/j.jssc.2003.02.007

S. Tariolle et al. Journal of Solid State Chemistry 177(2004)487-492 where Gp is the fracture energy of the porous layer, Gd liquid phase sintered [1o](sintering aid: YAG/alumina that of the dense layer eutectic 5 wt %). According to Eq (3), a minimum of porosity is Boron carbide(B C powder: Tetrabor 3000F, Wacker required to initiate crack deflection at the interface Ceramics, mean diameter 0.75 um) samples were solid between porous and dense layers, this porosity is phase sintered [11-14(sintering aid: phenolic resin 37 vol% and it was confirmed experimentally in Sic [4] 9 wt%(Novolac PN320, Solutia France) and alumina [5] specimens. To verify these energetic criteria, we have underta 2. 2. Sample processing the study of different multi-layered materials fabric Proportions of different components used for the Sic(alternate dense-porous) densified by liquid fabrication of B.C tapes are given in Table 1, the volume phase sintering, this mode of sintering has not been percentage of the main constituents in green tapes in used for this type of laminar composite up to now. Fig. I, respectively B4C(alternate dense-porous)densified by solid phase Notably, there is a high amount of organic ac sintering, that also is a new laminar system. especially in tapes containing PFA, which B4C with weak graphite interfaces has been produced induces burn-out difficulties, requiring to perform LOO burn-out with very slow heating rate Preparation of SiC and BC slurries was very similar The used processing steps are shown in the flow chart 2. Experimental The different constituents were milled and mixed at Different types of materials were prepare different rotation speeds. After de-airing at a very slow rotation speed and verifying the viscosity, slurries were Monolithic rnate dense-porous specimens tape cast. The tapes were cut, stacked in a predefined for Sic (the on process is fully described in sequence and thermo-compacted under a pressure of Ref.四9] 60 MPa at a temperature of 70C. Then, the samples Monolithic and alternate dense-porous specimens for were debindered and pyrolyzed (in air for SiC and in B4C. argon atmosphere for B. C)at very slow heating rate and finally they were sintered in VAS (Vide App Tape casting and thermocompression processing was System)graphite fur chosen to prepare multi-layered materials. This techni- arace under argon atmosphere(at 1950C for I h for SiC and at 2150C for I h for B.C) que allows to obtain thick and uniform layers. First the different constituents of the tape casting slurry will Table I be presented. Then, the preparation of the samples Composition of green tapes for B,C in wt% will be explained. Finally, techniques of characterization will be given. Dense layer Porous layer Porous layer (PFA) (under-sintered) 2.1. Ceramic powders and organic additives Ceramic 63 Dispersant Sintering agent 12.5 0 Slurries for tape-casting usually contain a mix of PFA different organic compounds. As organic solvent, the MEK-Ethanol azeotrope(60 vol% butanone-2 /40 vol% Plasticizer ethanol) was used. As dispersant, Beycostat C213 (CECA-France) was used to disperse the ceram 100% wder. An Organic ensured the cohesion and the flexibility of the tape, 口PFA respectively. Polyamide powders(mean diameter: 4.7, ■ Ceramic 10.5 and 20.7 um, PAl2, Orgasol, Atofina, France) together with corn starch (mean diameter: 14 Roquette, france) were used as pore forming agents 20% PFA). For SiC, a powder of graphite platelets(mean size:8×8×3μm3, Union Carbide) was used. For B4c, a graphite spray(Graphene. Orapi) was utilized to make Silicon carbide (Sic powder: Sika Tech FCP13 Norton-Norway, mean diameter I um) samples were Fig. 1. Volume percentage of main constituents in green tapes for B.C

where Gp is the fracture energy of the porous layer, Gd that of the dense layer. According to Eq. (3), a minimum of porosity is required to initiate crack deflection at the interface between porous and dense layers, this porosity is 37 vol% and it was confirmed experimentally in SiC [4] and alumina [5] specimens. To verify these energeticcriteria, we have undertaken the study of different multi-layered materials fabricated by tape-casting: * SiC (alternate dense–porous) densified by liquid phase sintering, this mode of sintering has not been used for this type of laminar composite up to now. * B4C (alternate dense–porous) densified by solid phase sintering, that also is a new laminar system. * B4C with weak graphite interfaces has been produced too. 2. Experimental Different types of materials were prepared: * Monolithicand alternate dense–porous specimens for SiC (the elaboration process is fully described in Ref. [9]). * Monolithicand alternate dense–porous specimens for B4C. Tape casting and thermocompression processing was chosen to prepare multi-layered materials. This technique allows to obtain thick and uniform layers. First, the different constituents of the tape casting slurry will be presented. Then, the preparation of the samples will be explained. Finally, techniques of characterization will be given. 2.1. Ceramic powders and organic additives Slurries for tape-casting usually contain a mix of different organiccompounds. As organicsolvent, the MEK-Ethanol azeotrope (60 vol% butanone-2/40 vol% ethanol) was used. As dispersant, Beycostat C213 (CECA-France) was used to disperse the ceramic powder. An acrylic binder and a phthalate plasticizer ensured the cohesion and the flexibility of the tape, respectively. Polyamide powders (mean diameter: 4.7, 10.5 and 20.7 mm, PA12, Orgasol, Atofina, France) together with corn starch (mean diameter: 14 mm, Roquette, France) were used as pore forming agents (PFA). For SiC, a powder of graphite platelets (mean size: 8 8 3 mm3 , Union Carbide) was used. For B4C, a graphite spray (Graphe`ne, Orapi) was utilized to make weak interlayers. Silicon carbide (SiC powder: Sika Tech FCP13, Norton-Norway, mean diameter 1 mm) samples were liquid phase sintered [10] (sintering aid: YAG/alumina eutectic 5 wt%). Boron carbide (B4C powder: Tetrabor 3000F, Wacker Ceramics, mean diameter 0.75 mm) samples were solid phase sintered [11–14] (sintering aid: phenolicresin 9 wt% (NovolacPN320, Solutia France). 2.2. Sample processing Proportions of different components used for the fabrication of B4C tapes are given in Table 1, the volume percentage of the main constituents in green tapes in Fig. 1, respectively. Notably, there is a high amount of organicadditives, especially in tapes containing PFA, which further induces burn-out difficulties, requiring to perform burn-out with very slow heating rate. Preparation of SiC and B4C slurries was very similar. The used processing steps are shown in the flow chart (Fig. 2). The different constituents were milled and mixed at different rotation speeds. After de-airing at a very slow rotation speed and verifying the viscosity, slurries were tape cast. The tapes were cut, stacked in a predefined sequence and thermo-compacted under a pressure of 60 MPa at a temperature of 70C. Then, the samples were debindered and pyrolyzed (in air for SiC and in argon atmosphere for B4C) at very slow heating rate and finally they were sintered in VAS (Vide Appareillage System) graphite furnace under argon atmosphere (at 1950C for 1 h for SiC and at 2150C for 1 h for B4C). ARTICLE IN PRESS Table 1 Composition of green tapes for B4C in wt% Dense layer Porous layer (PFA) Porous layer (under-sintered) Ceramic63 28.8 72 Dispersant 2.3 1 2.6 Sintering agent 12.5 5.7 0 PFA 0 50 0 Binder 9.5 6.2 12.7 Plasticizer 12.7 8.3 12.7 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Organic PFA Dense layer Porous layer (PFA) Porous layer (undersintered) Ceramic Fig. 1. Volume percentage of main constituents in green tapes for B4C. 488 S. Tariolle et al. / Journal of Solid State Chemistry 177 (2004) 487–492

S. Tariolle et al. / Journal of Solid State Chemistry 177(2004)487-49 Milling/ mixing Polyamide powders allowed to obtain different pore olvent dispersant+ ceramic powder sizes(from 4 to 20 um), corn starch led to spherical pores of approximately 10 um. Corn starch led to the Addition of Binder plasticizer highest level of porosity (47 vol% for 55 vol% of corn starch). In addition, the pyrolyzation was easier with starch [Addition of Pore forming agent In the multi-layered materials, the thickness was 7O um for dense layers and 80 um for porous layers De-airing The microstructure of dense layers and of ligaments in porous layers were similar (grain size 1.2 um, aspe ape casting ratio 1.6)191 Different types of multi-layered materials were pre- Thermo-compaction are Alternate dense-porous materials with porous layer Burning out made with pore forming agent or with porous layer made in the absence of sintering aid: Whatever the material, the Sintering layers had uniform thickness and were parallel each Fig. 2. Steps for preparation of ceramic-ceramic laminates. other. The grain size in the porous layers was similar to that of the dense ones. The mean grain size was 0.8 um Specimens were diamond polished using different The porosity in the layer made with corn starch was terconnected and had a mean size of 10 um. In the stages to obtain a mirror finish. To reveal the micro- porous layer made in the absence of sintering aid, the structure, materials were etched. For B.C, polished porosity was finer surfaces were electrolytically etched with KOH solution Weak interfaces made with graphite spray: These For SiC, polished surfaces were plasma etched (in specimens were produced by graphite coating via CF4/8 vol% O2 atmosphere) spraying and drying on each layer of B4C before thermocompaction. However, this method led to pro- 2.3. Sample characterization blems of uniformity and reproducibility of the weak interfaces Density of materials was calculated from measured Dense layers had a thickness of 100 um(Fig. 4)and eight and the geometrically determined volume. The a relative density of 0.94 porosity was determined by helium pycnometry for closed porosity; however, the size distribution and 3. 2. fracture behavior proportion of open porosity were determined by 3. 2. Sic Image analysis was used for characterization of grain Mechanical properties of monolithic materials have been measured: Young modulus, toughness, fracture and pore size using micrographs obtained by optical energy [15]. Clegg's criterion Eq (3)predicted crack microscopy(for porosity) and SEM(for grain size) Crack propagation in multi-layered materials was deflection for the SiC alternate multi-layered materials evaluated using 3 point-bending fracture tests on with porous layers containing a porosity larger than notched specimens (20mm span, INSTRON 8562, 37 vol%. but no significant crack deflection was displacement measured by LVDT sensor, cross-head observed in our case(Fig. 5) speed 0.025 mm/min) Two issues must be considered in a discussion of the results. First, if we consider the second phase, at grain boundaries, formed by the sintering additives, the chemical composition of this phase, determined from 3. Results and discussion local chemical analysis, continuously changes from layers and there brunt chan 3. Macrostructural and microstructural in fracture energy. As a consequence of this difference in characterization the chemistry between the dense layers and the ligament the 3.. Sic Secondly, the use of graphite platelets appears Different polyamide powders and corn starch were more favorable to deflect cracks than equi-axed corn tested as pore forming agents [91 starch. Then, pore shape appears to be an important

Specimens were diamond polished using different stages to obtain a mirror finish. To reveal the microstructure, materials were etched. For B4C, polished surfaces were electrolytically etched with KOH solution. For SiC, polished surfaces were plasma etched (in CF4/8 vol% O2 atmosphere). 2.3. Sample characterization Density of materials was calculated from measured weight and the geometrically determined volume. The porosity was determined by helium pycnometry for closed porosity; however, the size distribution and proportion of open porosity were determined by mercury porosimetry. Image analysis was used for characterization of grain and pore size using micrographs obtained by optical microscopy (for porosity) and SEM (for grain size). Crack propagation in multi-layered materials was evaluated using 3 point-bending fracture tests on notched specimens (20 mm span, INSTRON 8562, displacement measured by LVDT sensor, cross-head speed 0.025 mm/min). 3. Results and discussion 3.1. Macrostructural and microstructural characterization 3.1.1. SiC Different polyamide powders and corn starch were tested as pore forming agents [9]. Polyamide powders allowed to obtain different pore sizes (from 4 to 20 mm), corn starch led to spherical pores of approximately 10 mm. Corn starch led to the highest level of porosity (47 vol% for 55 vol% of corn starch). In addition, the pyrolyzation was easier with starch. In the multi-layered materials, the thickness was 70 mm for dense layers and 80 mm for porous layers. The microstructure of dense layers and of ligaments in porous layers were similar (grain size 1.2 mm, aspect ratio 1.6) [9]. 3.1.2. B4C Different types of multi-layered materials were prepared (Fig. 3, Table 2): Alternate dense–porous materials with porous layer made with pore forming agent or with porous layer made in the absence of sintering aid: Whatever the material, the layers had uniform thickness and were parallel each other. The grain size in the porous layers was similar to that of the dense ones. The mean grain size was 0.8 mm. The porosity in the layer made with corn starch was interconnected and had a mean size of 10 mm. In the porous layer made in the absence of sintering aid, the porosity was finer. Weak interfaces made with graphite spray: These specimens were produced by graphite coating via spraying and drying on each layer of B4C before thermocompaction. However, this method led to problems of uniformity and reproducibility of the weak interfaces. Dense layers had a thickness of 100 mm (Fig. 4) and a relative density of 0.94. 3.2. Fracture behavior 3.2.1. SiC Mechanical properties of monolithic materials have been measured: Young modulus, toughness, fracture energy [15]. Clegg’s criterion Eq. (3) predicted crack deflection for the SiC alternate multi-layered materials with porous layers containing a porosity larger than 37 vol%, but no significant crack deflection was observed in our case (Fig. 5). Two issues must be considered in a discussion of the results. First, if we consider the second phase, at grain boundaries, formed by the sintering additives, the chemical composition of this phase, determined from local chemical analysis, continuously changes from dense to porous layers and there are no abrupt changes in fracture energy. As a consequence of this difference in the chemistry between the dense layers and the ligament in the porous layers, Eq. (3) is no longer valid. Secondly, the use of graphite platelets appears more favorable to deflect cracks than equi-axed corn starch. Then, pore shape appears to be an important ARTICLE IN PRESS Addition of Binder + Plasticizer Milling / Mixing Solvent + dispersant+ ceramic powder Addition of Pore forming agent De-airing Tape casting Stacking Thermo-compaction Burning out Sintering Fig. 2. Steps for preparation of ceramic–ceramic laminates. S. Tariolle et al. / Journal of Solid State Chemistry 177 (2004) 487–492 489

characteristic. Lengthened pores aligned in the plane of the layers (Fig. 6a) seem to be more efficient that circular pores (Fig. 6b). 3.2.2. B4C The pictures and graphs (Fig. 7) show the crack propagation and the associated strain versus displacement curves in the different cases of laminar B4C materials. In cases (a) and (b), the rupture of the samples remains purely brittle. There is no reinforcement of materials. However, in cases (c) and (d), crack deflection took place at the interfaces. The rupture is no more brittle and the work of fracture is improved. 4. Conclusions Different SiC and B4C multi-layered materials were prepared by using tape casting and thermocompression. Characteristics of specimens were in agreement with those required to initiate crack deflection according to Clegg et al. [4,5]. Even though specimens had the required level of porosity, significant crack deflection did not occur in liquid phase sintered SiC specimens. The absence of crack deflection at the interfaces may be linked to the continuous variation of properties (rupture energy) from dense to porous layers due to the presence ARTICLE IN PRESS (a) (b) (c) Fig. 3. Micrographs of multi-layered B4C materials: (a) black porous layers made with 50 vol% of corn starch, (b) black porous layers made with 55 vol% of corn starch, (c) dark grey porous layers made in absence of sintering aid. Table 2 Thickness and density of layers in different B4C multi-layered materials Dense layer Porous layer Thickness (mm) Relative density Thickness (mm) Relative density a (50 vol% corn starch) 150 0.94 100 0.55 b (55 vol% corn starch) 150 0.94 100 0.50 c(without sintering aid) 100 0.94 150 0.65 Fig. 4. Micrograph of multi-layered B4C with weak interfaces formed by graphite coating. (a) (b) Fig. 5. Micrographs of SiC multi-layered materials: (a) porous layer made with corn starch P=46–47 vol%, (b) porous layer made with graphite platelets P=40–41 vol%. (a) (b) 20µm 20µm Fig. 6. Pore shape made by graphite platelets (a) or by polyamide powder (b) in SiC laminates. 490 S. Tariolle et al. / Journal of Solid State Chemistry 177 (2004) 487–492

of a second phase at the silicon carbide grain boundaries formed by sintering aids. In the case of the solid phase sintered B4C multilayered materials, significant crack deflection was observed in few specimens. The shape of pores seems to be a crucial parameter and elongated pores aligned with the plane of the layers seem to be more favorable to initiate crack deflection. Studies on B4C multi-layered materials containing weak interfaces like platelets of graphite or boron nitride are in progress to verify these conclusions. References [1] W.J. Clegg, Acta Metall. Mater. 40 (11) (1992) 3085–3093. [2] H. Liu, S.M. Hsu, J. Am. Ceram. Soc. 79 (9) (1996) 2452–2457. [3] D.H. Kuo, W.M. Kriven, Mater. Sci. Eng. A 241 (1998) 241–250. [4] K.S. Blanks, A. Kristoffersson, E. Carlstro¨m, W.J. Clegg, J. Eur. Ceram. Soc. 18 (1998) 1945–1951. [5] J.B. Davis, A. Kristoffersson, E. Carlstro¨m, W.J. Clegg, J. Am. Ceram. Soc. 83 (10) (2000) 2369–2374. [6] W. Lee, S.J. Howard, W.J. Clegg, Acta Mater. 44 (10) (1996) 3905–3922. [7] C. Lacroix, D. Leguillon, E. Martin, Compos. Sci. Technol. 62 (2002) 519–523. [8] M.-Y. He, J.W. Hutchinson, J. Appl. Mech. 56 (1989) 270–278. ARTICLE IN PRESS 0 20 40 60 80 100 120 strain (MPa) 0 20 40 60 80 strain (MPa) strain (MPa) strain (MPa) 0.0 0.2 0.4 0 10 20 30 40 50 60 70 80 90 0 20 40 60 80 100 120 1 mm 1 mm 1 mm 1 mm Porous layers densified without sintering aid (35 vol% of porosity) 0.00 0.02 0.04 displacement (mm) 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.00 0.02 0.04 displacement (mm) displacement (mm) 0.06 0.08 0.10 0.12 0.14 0.16 0.18 200 180 160 140 120 100 0.1 0.3 0.5 0.0 0.2 0.4 displacement (mm) 0.1 0.3 Weak interlayers made with a graphite spray Porous layers made with 55 vol%of corn starch (50 vol% of porosity) Porous layers made with 50 vol%of corn starch (45 vol% of porosity) (a) (b) (c) (d) Fig. 7. Fractographies and strain versus displacement curves of different B4C laminar materials. S. Tariolle et al. / Journal of Solid State Chemistry 177 (2004) 487–492 491

《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_porous-sIC-1

《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_porous-sIC-1