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Surface Monitoring of CFRP Structures for Adhesive BondingAdhesive bonding of composite materials requires reliable monitoring and detection of surface contaminants to assure robust and durable bonded structures. Surface treatment and effective monitoring prior to bonding is essential in order to obtain a surface free from contaminants that may degrade structural performance. Two techniques which monitor the effectiveness of the laser surface treatment of carbon fiber reinforced polymer (CFRP) materials are being investigated: laser induced breakdown spectroscopy (LIBS) and optically stimulated electron emission (OSEE). The applicability of LIBS to detect silicone contaminants on CFRP composites is studied using ~35 ns Nd:YAG laser pulses at 355 nm with a pulse energy of 45 mJ. The LIBS regime in which pulse energies are < 100 mJ is referred to as mLIBS. CFRP surfaces were contaminated with polydimethylsiloxane (PDMS), a major component of silicone based mold release agents. The presence of PDMS is found by inspecting the Si I emission line at 288.2 nm. Untreated CFRP samples and CFRP contaminated with PDMS were tested. The PDMS areal density ranged from 0.36 Â+/- 0.04 to 0.51 Â+/- 0.16 mg/cm2. The results demonstrate the successful detection of PDMS on CFRP using mLIBS. In addition, OSEE was used to measure CFRP surface cleanliness pre- and post-treatment by laser ablation on specimens contaminated with PDMS coatings from 8 nm to 1311 nm in thickness. The results showed a significant increase in the OSEE photocurrent after laser surface treatment.
Document ID
20170002059
Document Type
Conference Paper
Authors
Ledesma, Rodolfo (Virginia Univ. Charlottesville, VA, United States)
Palmieri, Frank L. (NASA Langley Research Center Hampton, VA, United States)
Yost, William T. (NASA Langley Research Center Hampton, VA, United States)
Connell, John W. (NASA Langley Research Center Hampton, VA, United States)
Fitz-Gerald, James M. (Virginia Univ. Charlottesville, VA, United States)
Date Acquired
March 9, 2017
Publication Date
February 26, 2017
Subject Category
Composite Materials
Report/Patent Number
NF1676L-25287
Meeting Information
2017 Annual Meeting of the Adhesion Society(St. Petersburg, FL)
Funding Number(s)
WBS: WBS 826611.04.07.03.05
Distribution Limits
Public
Copyright
Public Use Permitted.

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