R. Jones et al. /Composites: Part A 30(1999)569-575 Pre Ceramic Polym Solution(Si-N-c) 350·450F Re-impregnate Pre-ceramic polyme Cycles ( Finished Composite) Fig. 1. The PIP hand lay-up pro 3. Ceramic powder fillers of either silicon nitride(asi3N4) or silicon carbide(Bsic) 4. Boron nitride interface coating Table I summarizes the properties of the two reinforce- ments. Both have good tensile strength but HI-Nicalon has a higher elastic modulus than Cg Nicalon. HI-Nicalon was slightly more dense and was lower in oxygen content than CG Nicalon. The low oxygen content of HI-Nicalon, 0.5 wt%, is the source of improved thermal stability compared to CG Nicalon. HI-Nicalon can also be processed to higher temperature as a result of its higher thermal stability Fig. 2 shows the boron nitride interface coating used in this work. The coating is uniform, relatively smooth and continuous and shows very little bridging between fibers Coating thickness ranges from 0.3 to 0.7 um. A typical as- nade microstructure for the composite is shown in Fig 3. 25 4125 I The optical micrograph shows warp and fill fibers from the 0790 ply lay-up used to fabricate these two dimensionally Comparision of CG Nicalon and HI-Nicalon fiber properties CG Nicalon HI-Nicalon 2.97 Elastic modulus(GPa) 193 Filaments diameter(um) 2.55 74 Denier (g 9000 m 1800 1800 Composition(wt%) 25 4125 12 0.5 Fig. 2. SEM of bn coated Nicalon fiber3. Ceramic powder fillers of either silicon nitride (aSi3N4) or silicon carbide (bSiC). 4. Boron nitride interface coating. Table 1 summarizes the properties of the two reinforce￾ments. Both have good tensile strength but HI-Nicalon has a higher elastic modulus than CG Nicalon. HI-Nicalon was slightly more dense and was lower in oxygen content than CG Nicalon. The low oxygen content of HI-Nicalon, 0.5 wt%, is the source of improved thermal stability compared to CG Nicalon. HI-Nicalon can also be processed to higher temperature as a result of its higher thermal stability. Fig. 2 shows the boron nitride interface coating used in this work. The coating is uniform, relatively smooth and continuous and shows very little bridging between fibers. Coating thickness ranges from 0.3 to 0.7 mm. A typical as￾made microstructure for the composite is shown in Fig. 3. The optical micrograph shows warp and fill fibers from the 08/908 ply lay-up used to fabricate these two dimensionally 570 R. Jones et al. / Composites: Part A 30 (1999) 569–575 Fig. 1. The PIP hand lay-up process. Table 1 Comparision of CG Nicalon and HI-Nicalon fiber properties CG Nicalon HI-Nicalon Tensile strengh (GPa) 2.97 2.76 Elastic modulus (GPa) 193 269 Filaments diameter (mm) 15 14 Bulk density, (g cm23 ) 2.55 2.74 Filament/tow 500 500 Denier (g 9000 m21 ) 1800 1800 Composition (wt%) Silcon 58 63.7 Carbon 31 35.8 Oxygen 11 0.5 Fig. 2. SEM of BN coated Nicalon fiber