Ultrasonic C-scan

Fig. 8.12. (a) X-ray radiograph and (b) ultrasonic C-scan image, showing edge delamination in the [ 30°/ 90 ]s laminate of T300 carbon 5208 epoxy matrix. system which has been subjected to axial tension. Reprinted from Kim (1989). with kind permission from FIsevier Science-NI.. Sara Burgerhart straat 25,... 

The ultrasonic C-scan technique is the most widely used nondestructive method of locating defects in the composite microstructure. The through transmission C-scan is easy to implement and a large composite panel can be scanned in a matter of minutes. The problem with this technique is that a C-scan cannot reveal the type of defect present. Hence, there is no way to determine if a flaw detected by the C-scan is due to incomplete contact of an interply interface or some other type of defect in the composite microstructure. 

The resin content in both composites is about 37% by weight. The porosity of the composites was characterized by ultrasonic C-scans. The test specimens of no measurable porosity were used. The resin specimens and the composite laminates were cured in a hydraulic press at 250 F and 75 psl for one hour, and subsequently postcured at the same temperature in the absence of pressure for another two hours. Additional curing for up to 16 hours in the case of HX-205 and F-185 resins showed no measurable changes in dynamic mechanical properties. 

Figure 1.7 (a) An ultrasonic C-scan image (across the width, W) of undamaged and 2 J impact damaged laminate and (b) response of pristine and damaged composite plate [20]. 

Mode I cyclic compression—compression tests on CFRP-impacted CFRP plates have been performed by Katerelos et al. [38]. The analysis relies on nondestructive testing (ultrasonic C-scan) and modelling for quantification of delamination resistance. In mode II tests, there is a choice between test parameters yielding no shear reversal or... 

Figure 16.33 Vibration-based identification of impact damage in quasi-isotropic CFRP through model updating. Top picture shows the ultrasonic C-scan of the specimen bottom picture shows the damage areas fitted in the FEM model [69].

In a subsequent paper [67], subpenetration impact testing and ultrasonic C-scanning/optical reflection microscopy were used to characterize the damage in the three Epikote 828 resin-based laminates. At impact energies as low as 1.75 J mm , the damage zone was identified as the classic cone-of-fracture , that is more extensive delamination was sustained towards the unimpacted surface. 

Figure 6.41 Ultrapac ultrasonic C-scan equipment and a t)fpical C-scan image...

Figure 17.94 Ultrasonic C-scan of cfrp laminate showing an area of impact induced delamination white indicates negligible damage and black bad damage. Source Reprinted from Cawley P, The sensitivity of the mechanical impedance method of nondestructive testing, NDT Int, 30(4), 209-215, Aug 1987.

Smith RA, Clarke B, Ultrasonic C-scan determination of ply-stacking sequence in carbon fiber composites. Insight, 36(10), 741-747, 1994. 

Fig. 3. An ultrasonic C-scan image of two deliberate bonding defects shown by the dark areas between the dotted boundaries, in the bond area of a step lap joint. (From J L Rose, P A Meyer, Ultrasonic procedures for predicting adhesive bond strength.

Ultrasonic C-scan n. A non-destructive inspection technique for reinforced plastics in which the energy absorbed from a short ultrasonic pulse is measured. This is quantitatively different for sample containing delaminations, voids, or too little or too much reinforcement, than for solid samples of the correct composition. 

Figure 2. Low velocity impact of glass, Dyneema, Kevlar and carbon/epoxy laminates. Absorbed energy vers, damage area as measured by ultrasonic C-scan.

The pultruded part is evaluated by ultrasonic C-scan or ir scanning. Uniform fiber dispersion and even coating by the matrix resin are the main requirements. 

The surface is inspected visually during processing, but as in pultrusion, ultrasonic C-scan or ir scanning are valuable techniques. Uniform dispersion of the fibers and evenness of the resin coating are essential. 

Nondestructive tests applicable to filament-wound parts include ultrasonic C-scan and radiographic and visual inspection. 

Ultrasonic C-scan Good definition of material integrity, surface, and subsurface Expensive... 

Ultrasonic C-scan is standard for quality inspection of PMC plates (28), but the large signal attenuation with penetration depth limits this to thin plates. Lower frequency waves, eg, 0.5 MHz, yield larger penetration for equivalent attenuation, but the longer wavelengths limit the spatial resolution (eg, 6 mm for 0.5 MHz at 3000 m/s). 

Defect t5q>es frequently relate to the mechanism causing the indication. Many NDT methods have an intrinsic sensitivity for specific types of indications. Examples are ( ) ultrasonic C-scans sensitive to boundaries between materials of different acoustic impedance (eg, voids, delaminations), (2) X-ray radiography sensitive to variations in density (eg, inclusion of foreign objects, voids), and (5) acoustic emission sensitive to microscopic stress release (eg, crack growth). 

Imieh nska K, Castaings M, Wojtyra R, Haras J, Le Clezio E and Hosten B (2004) Ait-coupled ultrasonic C-scan technique in impact response testing of carbon fibre and hybrid glass, carbon and Kevlar/epoxy composites, J Mater Process Technol 157-158 513-522. 

Water bath used for ultrasonic C-scan inspection (From Adams et al. 1997]... 

Quality control of adhesively bonded joints is complex. There are two issues. First, is it possible to detect the presence or absence of adhesive, and second if the adhesive is present will it transmit loads between the two substrates Detecting the absence of adhesive in a joint is possible using techniques such as tapping, frequently used in boatyards, or ultrasonic C-scan. 

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