Abstract:
Composite structures are widely used in aircraft because they are lighter and stronger than metals. Laminated composite parts can be formed by automated tow placement. A large machine simultaneously places 1 2 to 30 ribbons (called "tows") of composite material onto a mandrel to form a part. Tows are positioned so that the edge of one is flush to the next without overlapping it. If there are laps or excessive gaps, the manufactured part will not meet its designed mechanical strength.
During a Phase I SBIR contract to the U.S. Air Force Wright Laboratory, QUEST Integrated, Inc. designed and built a prototype noncontact sensor to measure the widths of tows and gaps between tows during manufacture. Several approaches were investigated, including image processing with structured illumination and laser optical triangulation (LOT). The LOT approach was judged to be superior, but a commercial sensor did not perform well enough. QUEST designed and built custom optics and electronics for an improved dual LOT sensor. Algorithms to measure tow and gap width were derived. Shadowing of the returned laser beam was found to be an effective technique for gap detection. The sensor is designed to mount on a Cincinnati Milacron tow placement machine. In laboratory experiments the sensor was able to accurately detect and measure gap and tow width. We discuss these preliminary results and outline additional development needed. For additional details see (Folsom, 1 995).
Source: Proceedings of the 'NDE applied to Process Control of Composite Fabrication' - Conference, 1-2 Oct 1996 St. Louis, Missouri. Publisher and Organizer: Nondestructive Testing Information Analysis Center (NTIAC) Texas Research Institute Austin, Inc. Austin, Texas [http://www.ntiac.com] [Buying the Proceedings]
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