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Controlled Contamination of Epoxy Composites with PDMS and Removal by Laser AblationSurface preparation is critical to the performance of adhesively bonded composites. During manufacturing, minute quantities of mold release compounds are inevitably deposited on faying surfaces and may compromise bond performance. To ensure safety, mechanical fasteners and other crack arrest features must be installed in the bondlines of primary structures, which negates some advantages of adhesively bonded construction. Laser ablation is an automated, repeatable, and scalable process with high potential for the surface preparation of metals and composites in critical applications such as primary airframe structures. In this study, laser ablation is evaluated on composite surfaces for the removal of polydimethylsiloxane (PDMS), a common mold release material. Composite panels were contaminated uniformly with PDMS film thicknesses as low as 6.0 nm as measured by variable angle spectroscopic ellipsometry. Bond performance was assessed by mechanical testing using a 250 F cure, epoxy adhesive and compared with pre-bond surface inspection results. Water contact angle, optically stimulated electron emission, and laser induced breakdown spectroscopy were used to characterize contaminated and laser ablated surfaces. The failure mode obtained from double cantilever beam tests correlated well with surface characterization data. The test results indicated that even low levels of PDMS were not completely removed by laser ablation.
Document ID
20160009092
Acquisition Source
Langley Research Center
Document Type
Conference Paper
Authors
Palmieri, Frank (NASA Langley Research Center Hampton, VA, United States)
Ledesma, Rodolfo (Virginia Univ. Charlottesville, VA, United States)
Cataldo, Daniel (NASA Langley Research Center Hampton, VA, United States)
Lin, Yi (National Inst. of Aerospace Associates Hampton, VA, United States)
Wohl, Christopher (NASA Langley Research Center Hampton, VA, United States)
Gupta, Mool (Virginia Univ. Charlottesville, VA, United States)
Connell, John (NASA Langley Research Center Hampton, VA, United States)
Date Acquired
July 17, 2016
Publication Date
May 23, 2016
Subject Category
Composite Materials
Report/Patent Number
NF1676L-22982
Meeting Information
Meeting: SAMPE Long Beach 2016
Location: Long Beach, CA
Country: United States
Start Date: May 23, 2016
End Date: May 26, 2016
Sponsors: Society for the Advancement of Materials and Process Engineering
Funding Number(s)
WBS: WBS 826611.04.07.03.02
Distribution Limits
Public
Copyright
Public Use Permitted.

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