Laminated Carbon Fiber Composites (CFC) exhibit superior specific strength, stiffness and durability over metallic materials and over last few decades these composites have found extensive use in aerospace applications. However, in view of their anisotropy and deterioration of mechanical properties due to environmental degradation, structural validation tests are recommended at coupon and component level by certification authorities. In this paper, methodology employed to assess the structural integrity of a variety of T-300 class carbon fiber epoxy composite features and components has been described along with a few interesting case studies. Some CFC features and components like bold-pull- through specimens, spars and panels were subjected to Ultrasonic C-Scan before and after the application of failure loads with a view to assess the nature and extent of damage/delamination. In certain cases both Ultrasonic Pulse-Echo and Through-Transmission C-Scan methods were employed for proper characterization of damage/mode of failure. Based on the assessment of ultrasonic records obtained from both methods, it was evident that through- transmission C-Scan provided superior damage characterization for the class of composite material investigated in this study. The growth of delamination in both-pull-through specimen was found to be relatively smaller under hot-wet(100°C and 85% RH) environmental test condition compared to that under room temperature as-received condition, which is attributable to the plasticizing effect of the epoxy matrix in the former case. During compression buckling test on a CFC panel under simply- supported boundary condition, a loud pop in the post-buckling regime was initially presumed to be indicative of the delamination-failure of the panel. Upon unloading and analyzing the C-Scan record, it was confirmed that the structural integrity of the CFC panel was still intact and merely the GFRP-tabs at the end of the panel had got debonded under excessive load. The paper concludes with a positive note on the effectiveness of through-transmission C-Scan method in characterization of damage/delamination in carbon fiber composites.
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