Infrared inspection of advanced army composites

Abstract The development of a field portable infrared inspection system, complete with infrared imager, datarecording, digital image processing and analysis, and heat source for introduction of a thermal gradientis described. The system provides excellent portability with minimal reliance on on-site electric powerwhile maintaning excellent sensitivity to a variety ofdefects in typical U.S. Army composite structures.The portable system has demonstrated considerable flexibility in the nondestructive evaluation of adiverse assortment of composite structures for both aircraft and ground vehicle applications.1. Background: The U. S. Army continues to increase its use of advanced composites to obtain better performance of itsland and air systems. Composites provide the a variety of advantages including lighter weight, higherstrength, good damage tolerance and energy dissipation. Composite materials are currently deployedfor mission critical items, such as helicopter rotor blades and spa!! liners in armored vehicles. A widerange of applications are currently planned or are being considered. These include structuralcomponents for air and land based systems, such as the next generation of attack helicopters, whereextensive use of composites is planned in both rotor and ftiselage components, composite hulls forarmored vehicles, and composite bridge components.With the increased use of composites, more effective and efficient nondestructive testing methods areneeded to determine the health ofthese materials while they are deployed in the field. This will allowmission critical components to be evaluated between missions, insuring the integrity ofthe system priorto initiation of a mission. The requirements for such an inspection system include field deployability,high reliability, and easy transportability. It should also be able to rapidly, and in a noncontact fashion,scan the surface ofthe composite to minimize the time required to perform an inspection. An idealtechnique that satisfies all ofthese requirements is infrared thermography.2. The Inspection Problem