Ultrasonic and thermographic monitoring of impact induced damage of CFRP structures

Health monitoring of fiber composite structures is becoming increasingly important not only for aerospace structures, but also for consumer products including high performance sports equipment. One critical damage process is impact induced delamination, which might grow due to further loading until ultimate damage. First a short discussion and comparison is given on related monitoring techniques such as thermography, ultrasonics or lamb waves. Thereafter results of diverse structural parts are discussed. These include sandwich plates and bonded joints of truss structures for airships. Finally focus is given on curved structures, which are typical for rods as well as trusses found in high performance CFRP bicycle frames. Besides the state of stress, the curvature strongly influences the damage accumulation and propagation after impact. Hence, different pipe structures are monitored under alternating cyclic loading conditions using impulse echo ultrasonic and thermoelastic methods. The obtained monitoring results of damage accumulation and propagation will allow for better designs.