v.A. Krab et al. Composites Science and Technology 61(2001)1561-1570 50% notch 100% On=O MPa On=88 MPa attenuation pretest unnotched condition 2 mm 2 mm notch notch On=140 MPa 5 mm W=12.6mm n=150 MPa (d) Fig. 5. Ultrasonic C-scans of edge notched fracture specimens after varying levels of maximum applied load, ao/W=0. 2 for all specimens(a)Pretest condition,(b)pre-peak loading at on =88 MPa, (c)pre-peak loading at on=140 MPa,(d) post-peak loading on, peak- 150 MPa. three specimens monotonically loaded to a predetermined level, unloaded, and C-scanned. Following the C-scans. the specimens were sectioned, polished, and the observed damage documented. An untested specimen was also examined to determine the baseline condition of the as received material (specimen No. 1). Specimen No. 2 was loaded to on=88 MPa to examine damage which resulted Cut for polishing Cross-sectional view in nonlinearity in the load-CMOd behavior. Specimen notch No. 3 was loaded up to on=140 MPa to examine damage which resulted in nonlinearity in the measured ongitudinal strains ahead of the notch tip. Post peak damage was examined on specimen No 4 which was edge notched specimen loaded beyond the peak net section stress(on peak)=150 moved for destructive evaluation of C- scan damage Ultrasonic C-scans of specimens Nos. 1-4 are shown in Fig. 5 with the calibrated ultrasonic color bar. With reference to the color bar in Fig. 5(a), white indicates regions of high porosity exhibiting up to 75%attenua full scale signal transmission through the specimen, red tion. The C-scan of the unnotched, as received compo- indicates A-48 dB signal transmission(0.4% of the site in Fig. 5(a) shows the typical gray scale variation in full scale transmission). Due to the extensive pre-existing attenuation of approximately 0-50% away from the matrix cracks and porosity, C-scans of the untested com- edges of the specimen. C-scans of specimens that had posite showed varying levels of attenuation. These regions been loaded to sufficiently high stress showed levels of typically exhibited 0-50%attenuation, with isolated ultrasonic attenuation near the notch tip that exceededthree specimens monotonically loaded to a predetermined level, unloaded, and C-scanned. Following the C-scans, the specimens were sectioned, polished, and the observed damage documented. An untested specimen was also examined to determine the baseline condition of the as received material (specimen No. 1). Specimen No. 2 was loaded to n=88 MPa to examine damage which resulted in nonlinearity in the load-CMOD behavior. Specimen No. 3 was loaded up to n=140 MPa to examine damage which resulted in nonlinearity in the measured longitudinal strains ahead of the notch tip. Post peak damage was examined on specimen No.4 which was loaded beyond the peak net section stress (n, peak)=150 MPa. Ultrasonic C-scans of specimens Nos. 1–4 are shown in Fig. 5 with the calibrated ultrasonic color bar. With reference to the color bar in Fig. 5(a), white indicates full scale signal transmission through the specimen, red indicates 48 dB signal transmission (0.4% of the full scale transmission). Due to the extensive pre-existing matrix cracks and porosity, C-scans of the untested com￾posite showed varying levels of attenuation. These regions typically exhibited 0–50% attenuation, with isolated regions of high porosity exhibiting up to 75% attenua￾tion. The C-scan of the unnotched, as received compo￾site in Fig. 5(a) shows the typical gray scale variation in attenuation of approximately 0–50% away from the edges of the specimen. C-scans of specimens that had been loaded to sufficiently high stress showed levels of ultrasonic attenuation near the notch tip that exceeded Fig. 5. Ultrasonic C-scans of edge notched fracture specimens after varying levels of maximum applied load, a0/W=0.2 for all specimens. (a) Pretest condition, (b) pre-peak loading at n=88 MPa, (c) pre-peak loading at n=140 MPa, (d) post-peak loading n, peak=150 MPa. Fig. 6. Schematic edge notched test specimen showing material removed for destructive evaluation of C-scan damage zone. V.A. Kramb et al. / Composites Science and Technology 61 (2001) 1561–1570 1565