Abstract:
With the increased use of thermoplastic composites, sensing methods need to be developed and applied that enable the on-line measurement of porosity in the laminate. An increase in porosity leads to a decrease in density, modulus, and strength of the composite laminate. Therefore, the accurate measurement of the porosity content is critical to ensure consistent quality and high performance of composite structures. An on-line implementation of porosity sensors could lead to substantial cost reductions during the fabrication step by reducing rework and providing a feedback for the processing cycle.
Findings are presented that focus on and compare the use of two methods for on-line porosity measurements, infrared lock-in thermography and laser-based ultrasonics for surface acoustic wave measurements. These two methods have been down-selected from a number of initial candidates. To be successful, the candidate sensors would have to be able to detect low levels of porosity (about 1%) at a rate of over 10 in2/s while operating in a noisy and hot manufacturing environment.
An initial sensor evaluation procedure was established where a number of composite laminates with intentionally varied quality levels were prepared to conduct porosity measurements off-line. The results of this evaluation will be presented.
Recent research has been focused on the integration of the selected sensors with a prototype robotic tow placement workcell. Preliminary results from these on-line evaluations are encouraging.
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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