R. Jones et al. /Composites: Part A 30(1999)569-575 HI-Nicalon 200 oading Rate =0.01 MPa/sec 00.1020.3040.5060.70.80.91 Strain (%) Fig. 5. Elevated temperature tensile stress-strain curves for SiNCO matrix composites reinforced with Hl-Nicalon and CG Nicalon fiber 1.4 CG Nicalon 后 100°C 0 010002000300040005000600070008000 Fig. 6. Long term creep of CG Nicalon fiber reinforced SiNCO matrix composite. similar to the CG Nicalon composite but with a higher CG Nicalon composites can perform under moderate stress modulus in air for extended periods at 1100C. Fig. 6 shows a strain- ngth of the HI-Nicalon compo- time curve for CG Nicalon reinforced composite at 95 MPa site is higher than the CG Nicalon composite with compar- and 1100.C Creep tests were run for up to 6800 h for an able strain at room temperature, at elevated temperatures the individual specimen under these conditions. Testing of HI- strain of CG Nicalon reinforced composites increases sig Nicalon reinforced composites has shown a lower creep rate nificantly possibly because of fiber creep as shown in Fig. 5. compared to CG Nicalon. Fig. 7 shows a creep curve for the A number of investigators [5-10] have studied the creep two types of composites at 1200C. A CG Nicalon compo- behavior of cg nicalon and hi-nicalon fibers site failed at 1200C and 120 MPa in 215 h. The strain rate Recently, Lara-Curzio and Boisvert [11] studied the creep for the HI-Nicalon composite was much lower than for the behavior of these PIP composites. Their work suggests that CG Nicalon composite. The HI-Nicalon composite in thissimilar to the CG Nicalon composite but with a higher modulus. Although the ultimate strength of the HI-Nicalon compo￾site is higher than the CG Nicalon composite with compar￾able strain at room temperature, at elevated temperatures the strain of CG Nicalon reinforced composites increases sig￾nificantly possibly because of fiber creep as shown in Fig. 5. A number of investigators [5–10] have studied the creep behavior of CG Nicalon and HI-Nicalon fibers. Recently, Lara-Curzio and Boisvert [11] studied the creep behavior of these PIP composites. Their work suggests that CG Nicalon composites can perform under moderate stress in air for extended periods at 11008C. Fig. 6 shows a strain– time curve for CG Nicalon reinforced composite at 95 MPa and 11008C. Creep tests were run for up to 6800 h for an individual specimen under these conditions. Testing of HI￾Nicalon reinforced composites has shown a lower creep rate compared to CG Nicalon. Fig. 7 shows a creep curve for the two types of composites at 12008C. A CG Nicalon compo￾site failed at 12008C and 120 MPa in 215 h. The strain rate for the HI-Nicalon composite was much lower than for the CG Nicalon composite. The HI-Nicalon composite in this 572 R. Jones et al. / Composites: Part A 30 (1999) 569–575 Fig. 5. Elevated temperature tensile stress–strain curves for SiNCO matrix composites reinforced with HI-Nicalon and CG Nicalon fiber. Fig. 6. Long term creep of CG Nicalon fiber reinforced SiNCO matrix composite