different fiber/resin interfacial bonding and its HPHT hot-wet resistant capability between the glass fiber-filled PEEK and the carbon fiber-filled PEEK compounds. Micrographs in Figs. 36.22, 36.23, 36.24 and 36.25 present the microstructures and fiber/resin interfacial conditions in the molded chopped glass fiber-filled 450GL30 test samples after the hot-wet exposure in 3 % NaCl brine at 149 C (E149) and 204 C (E204) under 34.5 MPa for 240 h, respectively. From these micrographs, glass fiber fragility and fiber/resin interface debonding can be seen clearly in longitudinal and transverse cross sections of the 450GL30 samples after E149 and E204 hot-wet exposure. However, in the case of the chopped carbon fiber-filled 450CA30 molding compound, no evidence of degradation in carbon fibers and the carbon-fiber/resin interfacial bonding can be identified in longitudinal and transverse cross sections of the molded 450CA30 test samples after the hot-wet exposure in 3 % NaCl brine at 204 C (E204) and even at 232 C (E232) under 34.5 MPa for 240 h, respectively, as shown clearly in the micrographs presented in Figs. 36.26, 36.27, 36.28, and 36.29. Fig. 36.22 Micrograph on longitudinal cross section of a 450GL30 specimen after exposure in 3 % NaCl brine at 149 C, 34.5 MPa for 240 h (E149) Fig. 36.21 Micrograph ( 800) of a cross-section surface of a TP-1/S2-G laminate sample after exposure in 3 % NaCl brine at 177 C, 34.5 MPa for 240 h 36 HPHT Hot-Wet Resistance of Reinforcement Fibers and Fiber-Resin Interface of Advanced Composite Materials 307
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