v.A. Krab et al. Composites Science and Technology 61(2001)156/-1 75%. Specimens which were monotonically loaded and resulted in extensive attenuation ahead of the notch showed increased ultrasonic attenuation in the notch tip [Fig. 5(c). As shown in Fig. 5(d), continued loading region showed no change in the level of ultrasonic beyond the peak load resulted in further growth of the attenuation of the undamaged regions far from the attenuated region away from the notch tip notch tip. Therefore, attenuation of the ultrasonic signal Damage in the notch tip region was examined by exceeding 75% was identified as that which indicated destructive evaluation of the C-scanned specimens using damage accumulation during testing the sectioning procedure shown schematically in Fig. 6. The C-scans showed an increase in the ultrasonic First, excess material far from the C-scan damage zone attenuation around the notch tip region with an increase was removed above and below the notch plane. Second in the level of applied load. Specimen No. 2, loaded just the specimen was sectioned perpendicular to the notch beyond the load-CMOD linear region [Fig. 5(b)], the loading direction, just behind the notch tip. The spe showed slightly more attenuation around the notch tip cimens were polished along this through-thickness cross- than the as received composite [Fig. 5(a). Applied loads section so that a view of the damage ahead of the notch tip which result in nonlinearity in the longitudinal strains was obtained. The top surface matrix was removed on the specimen thickness =B re-existing matrix crack mm (b) looking in at notch tip (c) w-a savcut Fig. 7. SEM micrographs of the notch tip region for(a) an untested, as saw-cut, edge notched specimen. (b)after an applied net section stress an=88 MPa, (c)after on=140 MPa(d)after on, peak=150 MPa. The notch height, h=0.4 mm for all specimens75%. Specimens which were monotonically loaded and showed increased ultrasonic attenuation in the notch tip region showed no change in the level of ultrasonic attenuation of the undamaged regions far from the notch tip. Therefore, attenuation of the ultrasonic signal exceeding 75% was identified as that which indicated damage accumulation during testing. The C-scans showed an increase in the ultrasonic attenuation around the notch tip region with an increase in the level of applied load. Specimen No. 2, loaded just beyond the load-CMOD linear region [Fig. 5(b)], showed slightly more attenuation around the notch tip than the as received composite [Fig. 5(a)]. Applied loads which result in nonlinearity in the longitudinal strains resulted in extensive attenuation ahead of the notch [Fig. 5(c)]. As shown in Fig. 5(d), continued loading beyond the peak load resulted in further growth of the attenuated region away from the notch tip. Damage in the notch tip region was examined by destructive evaluation of the C-scanned specimens using the sectioning procedure shown schematically in Fig. 6. First, excess material far from the C-scan damage zone was removed above and below the notch plane. Second the specimen was sectioned perpendicular to the notch in the loading direction, just behind the notch tip. The spe￾cimens were polished along this through-thickness cross￾section so that a view of the damage ahead of the notch tip was obtained. The top surface matrix was removed on the Fig. 7. SEM micrographs of the notch tip region for (a) an untested, as saw-cut, edge notched specimen, (b) after an applied net section stress n=88 MPa, (c) after n=140 MPa (d) after n, peak=150 MPa. The notch height, h=0.4 mm for all specimens. 1566 V.A. Kramb et al. / Composites Science and Technology 61 (2001) 1561–1570