Evaluation of Alternative Peel Ply Surface Preparation Methods of SC-15 Epoxy / Fiberglass Composite Surfaces for Secondary Bonding

Report No. ARL-TR-6781
Authors: Jared M. Gardner; James P. Wolbert; Larry R. Holmes Jr.; Daphne D. Pappas
Date/Pages: January 2014; 50 pages
Abstract: Because of the extensive costs associated with building composite laminates, the U.S. Army is exploring approaches to reduce the processing steps associated with hybridized structures. One area of focus is in surface preparation for secondary bonding. An important quality of an effective surface preparation method is its ability to consistently provide clean and highly chemically active substrates for bonding. In this report, we examine peel ply surface preparation methods for secondary bonding of composite substrates using FM 94K epoxy film adhesive by mechanical testing, elemental surface analysis, and high-resolution imaging of failure surfaces. Woven S2 fiberglass infused with SC-15-toughened epoxy resin composite laminates was fabricated by the vacuum-assisted resin transfer molding process. Tool-side surfaces of the composites were prepared using nine commercial off-the-shelf peel plies, including dry and impregnated forms. Two preparation methods for bonding were investigated: peel ply only–prepared surfaces and peel ply in combination with grit blast–prepared surfaces. This report covers testing results concluded by a quantitative and qualitative analysis of the comparative effects of the preparation methods, technical challenges, and influential factors controlling peel ply effectiveness in bond performance, and recommendations for future work.
Distribution: Approved for public release
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Last Update / Reviewed: January 1, 2014