Determination of Micorcracking Damage in Composites

Rapid growth in the performance and capabilities of pulsed thermography, and the increased use of composite materials in the construction and repair of military and commercial aircraft, has strongly positioned it as a viable NDI technique. Thistechnology, as it currently stands, is a widely accepted rapid, non-contact, wide-area inspection tool. In Phase I of this program, Thermal Wave Imaging, Inc. proposes to leverage its expertise in this field coupled with work performed under previouslyawarded SBIR programs. Specifically, we will investigate development of a nondestructive method to inspect composite skin honeycomb components for micro-cracking, heat damage, and other defects related to excessive thermal and/or moisture exposure. Twosignificant modifications to the conventional pulsed thermography approach will be investigated for feasibility: (1) A low-energy, repetitive data acquisition scheme will be evaluated for measurement of material properties and depth of low level damage,(2) A hardware device to reduce the duration of the flash lamp pulse by an order of magnitude will be built and tested. Successful development and implementation of the proposed NDI pulsed thermography system, for detecting and quantifying size and depthof micro-cracking in composite skin plies, will fill a wide-spread void in current capability for both commercial and military aerospace industry segments. Conventional NDI techniques such as UT, X-ray, PT have shown limited success for this particularneed, not to mention long inspection times, high cost of operation, health and safety issues, and inadequate portability.Our Phase I proposal was formulated based on input from current and prospective customers in Government and private aerospace manufacturing, service, and R&D, including Air Force, Navy, NASA, commercial airline, and military NDE personnel. We found thatseveral major aerospace and power generation customers (Boeing, Airbus, GKN Westland, Lockheed-Martin, Siemens Westinghouse, GE) were still using conventional inspection techniques such as UT, X-ray, and PT for detection of micro-cracking with moderatesuccess, not to mention long inspection times, high cost of operation, health and safety issues, and inadequate portability. These customers indicated a high degree of interest in an NDI system that would incorporate the advanced features of the pulsedsystems that they were using on other applications.