wwceramics. org/ACT Cracking Resistance of Silicon Carbide Composites ○ Materials spec. o m, ITit me. L. Depth, a ofs Fig. I. Drawing of the single-edge notched bend (SENB)test NITE-Thick-Coat with a surface finish of l um for the crack extension observation. The radius of the notch root was approx- mately 150 um. The SENB tests were conducted at Fig. 2. Drawing of the double-notch tensile(DNT) test specimen room temperature in ambient air using an electrome- chanical testing machine ng a threepoint bend fixture with a support span(L) of 16 mm for SENB-1 3 and 32 mm for SENB-4. diamond saw. The radius of the notch root was The crack opening displacement(COD) was measured 150 um. The DNT tests were conducted at room by the clip-on-type gauge. The constant crosshead dis- temperature using an electromechanical testing machine placement rate was 0.1 mm/min. Unloading/reloading with a wedge-type gripping device. The COd was mea sequences were applied to evaluate the damage accumu- sured by a pair of Cod gauges. An average of two lation behavior during the test. In this paper, test results readings was applied in the calculation. A constant of NITE-Thick-Coat are reported. No data are pres- crosshead displacement rate was 0.5 mm/min. Unload ently available for NITE-Thin-Coat. Furthermore, en- ing/ reloading sequences were applied to evaluate the tire tests for PIP-Coat were invalid because of the damage accumulation behavior during the tests. The compressive failure at the loading point. Details are de- DNT tests were applied to all SiC/SiC composite types scribed in nozawa et al listed in table i Double-Notch Tensile(DNT) Test Figure 2 shows a photo image of the test setup and Microstructural Observation a drawing of the dNT test specimen. Notched tensile A crack extension length from the initial artificial specimens with a different initial notch depth(ao)were tch was measured using optical microscopy. For this used. For comparison, unnotched rectangular tensile purpose, replica films of the surface microstructure of the specimens (40 mm x 4mm x 1.5 mm) with a gauge specimen were taken at each unloading point for SeNB length of 15 mm were tested. The number of test spec- tests. For DNT tests, the crack extension length could not mens are also listed in Fig. 2. The fiber longitudinal be measured primarily due to unstable crack extension just direction was set parallel to the loading direction. Test prior fracture. Fracture surfaces were observed using field- hined from the composite plate by mission scanning electron microscopywith a surface finish of B1 mm for the crack extension observation. The radius of the notch root was approx￾imately 150 mm. The SENB tests were conducted at room temperature in ambient air using an electrome￾chanical testing machine. Test specimens were loaded using a threepoint bend fixture with a support span (L) of 16 mm for SENB-1 B3 and 32 mm for SENB-4. The crack opening displacement (COD) was measured by the clip-on-type gauge. The constant crosshead dis￾placement rate was 0.1 mm/min. Unloading/reloading sequences were applied to evaluate the damage accumu￾lation behavior during the test. In this paper, test results of NITE-Thick-Coat are reported. No data are pres￾ently available for NITE-Thin-Coat. Furthermore, en￾tire tests for PIP-Coat were invalid because of the compressive failure at the loading point. Details are de￾scribed in Nozawa et al.18 Double-Notch Tensile (DNT) Test Figure 2 shows a photo image of the test setup and a drawing of the DNT test specimen. Notched tensile specimens with a different initial notch depth (a0) were used. For comparison, unnotched rectangular tensile specimens (40 mm 4 mm 1.5 mm) with a gauge length of 15 mm were tested. The number of test spec￾imens are also listed in Fig. 2. The fiber longitudinal direction was set parallel to the loading direction. Test coupons were machined from the composite plate by a diamond saw. The radius of the notch root was B150 mm. The DNT tests were conducted at room temperature using an electromechanical testing machine with a wedge-type gripping device. The COD was mea￾sured by a pair of COD gauges. An average of two readings was applied in the calculation. A constant crosshead displacement rate was 0.5 mm/min. Unload￾ing/reloading sequences were applied to evaluate the damage accumulation behavior during the tests. The DNT tests were applied to all SiC/SiC composite types listed in Table I. Microstructural Observation A crack extension length from the initial artificial notch was measured using optical microscopy. For this purpose, replica films of the surface microstructure of the specimen were taken at each unloading point for SENB tests. For DNT tests, the crack extension length could not be measured primarily due to unstable crack extension just prior fracture. Fracture surfaces were observed using field￾emission scanning electron microscopy. Fig. 2. Drawing of the double-notch tensile (DNT) test specimen. Fig. 1. Drawing of the single-edge notched bend (SENB) test specimen. www.ceramics.org/ACT Cracking Resistance of Silicon Carbide Composites 307