D. Koch et aL Composites Science and Technology 68(2008)1165-1172 Table 1 ies of various CMC classified in Fig 4(as far as available from literature Material type Manufacturing method [6] Carbon T-300/Carbon, 16 layers, 0/900 56% fiber content LPL 4 infiltrations [5 Al2O3 Almax/ZrO2 AlO3, 6 layers, 0/900 33% fiber content minicomposite No detailed processing descripti Carbon Torayka M-40/Carbon, 15 layers, 0/90 50% fiber content Preformed yarn method LPI /C Sigrabond 1501 G, 24 layers, 0/90 open porosity 10-12% LPI Preformed 87x图2 [8 Carbon Torayka M40/C, 16 layers, 0 /90 50%fiber cont Nextel 720 /mullite and alumina, 12 layers, 0/900 39% fiber content matrix porosity 38% CSI up to [10] Nextel 610/80% mullite and 20% alumina 0/90 composite porosity 22-25% matrix porosity 38-42% CSI up to T800C/SiC 4 UD 0°/90° WHIPOX0°/90° Nicalon/MAS 12 0/900 40% fiber content fully dense MAS matrix Hot pressing Nicalon Sic/SiC 32% fiber content 8. 6% matrix porosity Nicalon SiC/SiC 0/90 plain weave 35% fiber content residual porosity 10-15% The characteristic difference between on-axis loading are infiltrated with the carbon matrix by several impregna (fibers are oriented in loading direction)and off-axis load- tion cycles with succeeding thermal treatments up to ing is manifested in Fig 3 for both composite types WIC 2000C. Finally, the resulting composite is characterized and WMC. Similar strength is measured for WIC under by an open porosity of 10-12% resulting from shrinkage both loading conditions, as discussed earlier on the base of micromechanical mechanisms On the contrary, in case of WMc the strength is strongly reduced under off-axis conditions because the fibers are not carrying the load sufficiently se I Longitudina The proposed concepts WIC and WMC are typical boundary examples with the real composites being situated somewhere in between. The properties of the composites not only depend on the manufacturing route, but also on d the chosen combination of fiber and matrix. In Fig. I it becomes obvious that with improved mechanical properties gD of the matrix the interfacial fracture energy plays a more important role and must be low enough in order to fulfill C 150/ →+1575 he boundary conditions of non brittle failure. This improvement of matrix properties can be reached by e. g reinfiltration cycles which is the regular case for the LPI process. Thus, if the matrix properties are enhanced the interfacial properties become more important. In Fig. 4 several composites from various sources are ranked con Strain (0%1900 and +45%/-459)as a measure of classification to b o WIC and WMC, respectively. Additionally, their proper- ties which were available from the literature are listed in q Table 1. It turns out that a typical WMC like C/C shows a high Eo/E4se ratio while a typical WIC like Nicalon/ +15%75° SiC is characterized by a Eoo/E4se ratio of 1. Other compos- 2 ites like oxide/oxide composites, LPI derived materials, and Sic fiber reinforced glass matrix composites are situated 090 between these boundary cases 方250 300 4. Materials and experiments ongitudinalTransverse Fundamental tests have been performed using a com- G」 mercially available C/C composite called Sigrabond 1501G(SGL Carbon, Germany). The material consists of 24 bidirectional reinforced layers of carbon fiber mats. Fig. 5. Typical stress strain curves of WMC composite C/C under(a) The composite is designed symmetrically and shows the tension and (b)compression with different angles between fiber orientation same properties in 00 and in 90 orientation. The fiber mats and loading directionThe characteristic difference between on-axis loading (fibers are oriented in loading direction) and off-axis load￾ing is manifested in Fig. 3 for both composite types WIC and WMC. Similar strength is measured for WIC under both loading conditions, as discussed earlier on the base of micromechanical mechanisms. On the contrary, in case of WMC the strength is strongly reduced under off-axis conditions because the fibers are not carrying the load sufficiently. The proposed concepts WIC and WMC are typical boundary examples with the real composites being situated somewhere in between. The properties of the composites not only depend on the manufacturing route, but also on the chosen combination of fiber and matrix. In Fig. 1 it becomes obvious that with improved mechanical properties of the matrix the interfacial fracture energy plays a more important role and must be low enough in order to fulfill the boundary conditions of non brittle failure. This improvement of matrix properties can be reached by e.g. reinfiltration cycles which is the regular case for the LPI process. Thus, if the matrix properties are enhanced the interfacial properties become more important. In Fig. 4 several composites from various sources are ranked con￾cerning their ratio of stiffness in on and off-axis orientation (0/90 and +45/45) as a measure of classification to WIC and WMC, respectively. Additionally, their proper￾ties which were available from the literature are listed in Table 1. It turns out that a typical WMC like C/C shows a high E0/E45 ratio while a typical WIC like Nicalon/ SiC is characterized by a E0/E45 ratio of 1. Other compos￾ites like oxide/oxide composites, LPI derived materials, and SiC fiber reinforced glass matrix composites are situated between these boundary cases. 4. Materials and experiments Fundamental tests have been performed using a com￾mercially available C/C composite called Sigrabond 1501G (SGL Carbon, Germany). The material consists of 24 bidirectional reinforced layers of carbon fiber mats. The composite is designed symmetrically and shows the same properties in 0 and in 90 orientation. The fiber mats are infiltrated with the carbon matrix by several impregna￾tion cycles with succeeding thermal treatments up to 2000 C. Finally, the resulting composite is characterized by an open porosity of 10–12% resulting from shrinkage Table 1 Properties of various CMC classified in Fig. 4 (as far as available from literature) Material type Manufacturing method [6] Carbon T-300/Carbon, 16 layers, 0/90 56% fiber content LPI, 4 reinfiltrations [5] Al2O3 Almax/ZrO2 + Al2O3, 6 layers, 0/90 33% fiber content minicomposite No detailed processing description [12] Carbon Torayka M-40 /Carbon, 15 layers, 0/90 50% fiber content Preformed yarn method LPI [x] C/C Sigrabond 1501 G, 24 layers, 0/90 open porosity 10–12% LPI [8] Carbon Torayka M40/C, 16 layers, 0/90 50% fiber content Preformed yarn method LPI [7] Nextel 720/mullite and alumina, 12 layers, 0/90 39% fiber content matrix porosity 38% CSI up to 1200 C [10] Nextel 610/80% mullite and 20% alumina 0/90 composite porosity 22–25% matrix porosity 38–42% CSI up to 1200 C [x] T800 C/SiC 4 UD layers 0/90 LPI [x] WHIPOX 0/90 open porosity 34% CSI [3] Nicalon/MAS 12 layers, 0/90 40% fiber content fully dense MAS matrix Hot pressing [3] Nicalon SiC/SiC 0/90 32% fiber content 8.6% matrix porosity CVI [2] Nicalon SiC/SiC 0/90 plain weave 35% fiber content residual porosity 10–15% CVI 0 50 100 150 200 250 300 350 400 -0.4 -0.2 0.0 0.2 0.4 Transverse Longitudinal +45°/-45° +15°/-75° +30°/-70° 0°/90° Strain [%] Stress [MPa] -400 -350 -300 -250 -200 -150 -100 -50 0 -0.4 -0.2 0.0 0.2 0.4 Longitudinal Transverse +45°/-45° +15°/-75° +10°/-80° 0°/90° Strain [%] Stress [MPa] ϕ σ σ σ ϕ σ Fig. 5. Typical stress strain curves of WMC composite C/C under (a) tension and (b) compression with different angles between fiber orientation and loading direction. 1168 D. Koch et al. / Composites Science and Technology 68 (2008) 1165–1172