Moisture ingression creates huge concerns on fiber reinforced composites because of the reduction in mechanical strengths with the moisture absorption and additional weight gains on the aircraft. If the appropriate techniques are used to predict the moisture ingression in the laminate composite structures, it will be of an immense advantage to detect moisture contents and their effects on the properties of the composites. Mechanisms of moisture influence in the composite structures also need to be thoroughly understood for a better design of new structural composites. This research study aims at investigating the effectiveness of different non-destructive inspection (NDI) techniques to detect moisture absorption. Carbon and glass fiber reinforced composite panels were prepared and used during the moisture ingression tests. Different NDI techniques, including ultrasonic through transmission and pulse echo, phase array, bondmaster and digital tap hammer were chosen to determine the moisture ingression levels. Throughout the tests, initial and final weights of the composite panels were determined using the high accuracy balances. NDI scanning parameters were kept constant for the tests. The effectiveness of each technique was determined and their results were discussed in detail.

Impact damages on the composites need to be understood thoroughly for the designing, manufacturing and repairing of the aircraft composite parts. Larger diameter of the impactor can create a shallow dent on the outside, but a significant damage on the inside of the composites. Larger impact dents can be easily detected during the regular visual inspection, while the smaller dents with significant internal damages cannot be detected which may compromise the structure resulting in safety concerns for the composite aircraft. 3D characterization of impact damages on glass, carbon, and Kevlar fibers reinforced composite structures may be necessary to better understand the material behavior and provide better designs. In the present study, Kevlar fiber composite panels were prepared using a wet layup in a vacuum curing oven while the glass and carbon weave material composite panels were fabricated using pre-preg and cured in the autoclave. These composite panels were impacted with 3 different tup diameters and 2 different energy levels. Impact load was measured using a load cell and the velocity was detected using a velocity detector. The impacted composite panels were then subjected to the non-destructive inspection (NDI) tests, and their 3D structural damages were evaluated in detail. The test results showed that the shallow dent impacts created significantly deeper and bigger internal damages on the structure of the composites. In addition to that, the impact damages on the composites were dependent on the composite types and structures, which may be critical for the design, manufacture and repair of different aircraft composites.