Investigations of moisture ingressions in composites via NDI techniques

Abstract

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.