Date of Award

Spring 1998

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Mechanical Engineering

Committee Director

Surendra N. Tiwari

Committee Director

Joseph M. Marchello

Committee Member

Ann C. Van Orden

Call Number for Print

Special Collections; LD4331.E56 G74

Abstract

A series of five experiments on the NASA Langley automated tow placement robot revealed stagnation of gas flow in the nip region. Since the torches could not heat effectively in the nip region, the roller temperature was the dominant influence on interlaminar bond strength. The roller temperatures required for high bond strength caused resin and fiber on the panel top surface to adhere to the compaction roller. Resin and fiber was pulled from the panel surface and wrapped around the roller, which was a severe processing problem. A supplemental radiant heat source was designed to permit reductions in roller temperature. The radiant heater was mounted to the existing robot hardware and tow placement trials were carried out. Designed experiments with the hybrid heat source revealed that the lamp output was the strongest influence on bond strength. Additional experiments identified optimal placement conditions. Panels placed at optimal conditions had mode I fracture toughness comparable to autoclave processed parts. However, roller sticking caused high void contents in these panels. Panels fabricated with reduced roller temperatures had lower fracture toughness. These panels had low void contents and were tow placed with no roller sticking problems. Elimination of roller sticking significantly improves the processability of high-viscosity thermoplastics. Additional optimization work should improve the bond strength obtainable with low roller temperatures. The addition of the radiant heat source made possible fabrication of parts that were extremely difficult to tow place with convective heating alone.

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DOI

10.25777/q18y-nc43

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