Impact Damage Detection of Toughened CFRP Laminates with Time Domain

Laminated Carbon Fiber Reinforced Polymer (CFRP) composites are very effective in weight saving in aeronautical structural components. For these laminated CFRP structures, it is, however, difficult to detect damage such as delamination, matrix cracks, and local fiber breakages caused by low velocity impact loading In the previous study in 2009, Time Domain Reflectometry (TDR) method was applied to a unidirectional laminated CFRP structure for the first time. In the previous study in2010, the research has been done on the application of the TDR method for the CFRP laminates. In the present study, therefore, actual impact damage is employed instead for the TDR. Electrical contact between fiber fragments exists in these micro-buckling although the electrical resistance becomes very high at the micro-buckling point. We have to investigate the applicability of the TDR method for the impact damage. A low speed impact test is performed to a cross-ply CFRP plate, and impact damage is made at the surface of the CFRP plate. TDR is applied to the cross-ply CFRP plate. The result shows that the reflected signal can be observed after the impact test. This result indicates that the TDR method is useful for detection of the low speed impact damages. Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE 30 JAN 2013 2. REPORT TYPE Final 3. DATES COVERED 11-10-2011 to 11-12-2012 4. TITLE AND SUBTITLE Impact Damage Detection of Toughened CFRP Laminates with Time Domain Reflectometry 5a. CONTRACT NUMBER FA23861114036