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CINCINNATI, OH, United States

Dillingham G.,Brighton Technologies Group, Inc
Annual Technical Conference - ANTEC, Conference Proceedings | Year: 2013

Surface treatments of metals and polymers are frequently necessary to control properties such as adhesion of paints and sealants. Because surface properties are determined by only the uppermost few molecular layers, measuring these properties in manufacturing environments can be challenging. Water contact angles can be obtained very rapidly and conveniently and provide sensitive, quantitative feedback of surface properties important for adhesion. Source


Dillingham G.,Brighton Technologies Group, Inc
Technical Paper - Society of Manufacturing Engineers | Year: 2014

The fundamental relationships between surface chemistry, surface morphology, and adhesion are briefly reviewed. The effect of typical metal and composite surface preparation processes on these surface properties is discussed. The use of wetting measurements to determine these properties and their ability to quantitatively predict failure mode and strength of adhesive/adherend interfaces is described. Industrial examples of these measurements are presented. Source


Giles Dillingham R.,Brighton Technologies Group, Inc
International SAMPE Technical Conference | Year: 2013

Metals present extremely high energy, reactive surfaces to the environment. When mechanically or chemically cleaned, they rapidly oxidize and adsorb contaminants such as organic vapors. Polymers present surfaces that are less reactive towards their surroundings. When cleaned by abrasion processes they also show rapid changes due to oxidation and adsorption, but these changes tend to be of lower magnitude. Successful bonded repair of aircraft structures involves creating a small area of carefully controlled surface composition on metallic or polymeric surfaces. This area to be bonded is located within a larger area of material that may be contaminated with a variety of soils picked up during normal aircraft operation: organic and inorganic soils, fuel, hydraulic fluids, etc. Because of the reactivity of freshly prepared surfaces and the proximity and mobility of contaminants in the surrounding area, cleaning of these surfaces sufficiently to obtain reliable adhesive bonds can be particularly difficult in field situations. Furthermore, because the difference between a well-cleaned surface and a contaminated one may only be a few molecular layers, it can be difficult for the technician to establish when the surface has been properly prepared. Measurement of the geometry of a liquid drop deposited onto the surface can be done extremely rapidly and form the basis of a sensitive check of surface cleanliness and consistency in a repair depot or in challenging field situations. This paper discusses the use of these rapid wetting measurements for quality assurance of surface treatments for adhesively bonded repairs. Copyright 2013 by Aurora Flight Sciences. Source


Giles Dillingham R.,Brighton Technologies Group, Inc
International SAMPE Technical Conference | Year: 2013

A primary consideration in adhesive bonding of composites is to create bonded structures that have predictable strength. The cohesive strengths of adhesives and composites are well understood and highly predictable. However, interfacial strength is a complex function of the interaction of the adhesive with the prepared substrate surface, and can be difficult to predict. For this reason interfacial failure is unacceptable, and failure mode may be a more important characteristic of composite-composite adhesive bonds than the ultimate strength. A somewhat weaker bond that always fails cohesively with a highly predictable failure load may be preferable to a stronger bond that fails interfacially on occasion due to poorly controlled surface treatment variables. Because of this, processes used to prepare a composite surface for bonding must be well understood and highly reproducible. This paper discusses the relationship between surface composition and failure mode, and demonstrates how conceptually simple measurements of the wetting properties of the surface with an inert probe fluid can be an excellent predictor of failure mode in bonded structures. Copyright 2013 by Aurora Flight Sciences. Source


Grant
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase II | Award Amount: 978.23K | Year: 2006

Surface energy is potentially the most critical predictor of performance for composite/composite adhesive bonds. It is straightforward to measure the surface energy of a planar composite using, for example, contact angle measurements obtained from a range of probe liquids. However, once a surface has been roughened on a microscopic scale by a process such as grit blasting, quantifying the surface energy becomes a much more difficult task. In Phase I it was demonstrated that the wetting behavior of a single carefully chosen probe liquid is an excellent predictor of subsequent adhesive bond performance, even on a highly roughened surface. It was further demonstrated that the probe liquid wetting behavior was well quantified by measuring the diameter of a small drop of known volume. This technique provides fundamental information about the relationship between contamination, surface energy and performance for adhesively bonded composites. Phase II will use this technique to evaluate a wide range of substrates, adhesives, and contaminants. A practical prototype measuring tool for evaluating surface energy using this technique will be constructed and evaluated in a manufacturing environment.

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