9457156 Mantell The goal of this research is to develop and implement a noncontact, nondestructive method for evaluating interlaminar bonding during in-situ consolidation of composites. An airborne acousto-ultrasonic technique will be implemented in closed loop control of tape laying. In the early phases of this research, the focus will be on developing a better understanding of airborne ultrasonic waves for detecting defects in composites. A theoretical model relating airborne acousto-ultrasonic operating parameters to the resulting stress wave will be developed and experimentally validated. The second phase of the research will entail sensing and evaluating bond quality off line using the proposed air contact NDE method. Specimens of varying thickness with an poorly bonded top most layer will be manufactured and tested. Nondestructive evaluation of bond strength will be compared with mechanical tests of the bond strength. In the final phase, the proposed air contact NDE method will be integrated into an existing tape laying apparatus. Following statistical design of experiment techniques, an empirical process model will be developed and a closed loop control algorithm implemented. This research is significant on several fronts. In processing of advanced materials via in-situ consolidation, adequate interlaminar bonding is critical to part structural integrity. Because cost of these materials is high, it is desirable to monitor part quality during processing. Defects identified during processing can be reworked immediately as part of the process control scheme; thereby improving yields and reducing scrap and costs. A noncontact method also offers portability to remote sites and on line (during manufacture) sensing capabilities. Moreover, similar methodologies could be applied to other in-situ consolidation and bonding processes.
