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Search Publications by: Donald L. Hunston (Assoc)

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Displaying 51 - 75 of 125

Adhesion Research at the National Institute of Standard and Technology (NIST)

March 11, 2009
Author(s)
Donald L. Hunston, Christopher M. Stafford
Over the years, NIST has been very active in adhesion research. Although there has never been an organizational group or large-scale program that focused specifically on this topic, a wide variety of projects have had adhesion, or related properties, as a

Effect of Strain on the Modulus of Sealants Exposed to the Outdoors

March 11, 2009
Author(s)
Christopher C. White, Donald L. Hunston, Kar T. Tan
The effects of applied strain on sealants exposed to outdoor weathering were examined for two sealant formulations, sealants A and C. Both static and dynamic strain was applied to the sealants during the summer in a Gaithersburg, MD-outdoor location. Both

Impact of Polymer Chemistry on the Durability of Model Adhesives Supported on SiOx Substrates in Humid Environments Using Homologous Series of Poly(n-alkyl methacrylate)s

January 7, 2009
Author(s)
Kar T. Tan, Bryan D. Vogt, Christopher C. White, Kristen Hamilton, Nicholas Wagman, Joshua E. Goldman, Jessica M. Torres, Kristen L. Steffens, Cyril Clerici, Sushil K. Satija, Donald L. Hunston
There are many advantages that structural adhesives can offer compared to the more traditional joining methods, such as welding, bolting, mechanical fastening, etc. However, there are some issues that currently limit the wider application of adhesives. One

Impact of Adhesive Modulus on Humidity Induced Failure

December 17, 2008
Author(s)
Kar T. Tan, Christopher C. White, Kristen Hamilton, Nicholas Wagman, Joshua E. Goldman, Alper Karul, Jessica M. Torres, Sushil K. Satija, Cyril Clerici, Donald L. Hunston, Bryan D. Vogt

Technique for Monitoring Environmentally Induced Changes in Polymeric Sealants

December 17, 2008
Author(s)
Donald L. Hunston, Kar T. Tan, Christopher C. White
A new procedure was developed to utilize stress relaxation tests to monitor damage induced in sealant materials exposed to environmental variables and changing strains. By combining tension and compression tests, it was possible to monitor both molecular

Durability of Building Joint Sealants

December 12, 2008
Author(s)
Christopher C. White, Kar T. Tan, Donald L. Hunston
Predicting the service life of building joint sealants exposed to service environments in less than real times has been a need of the sealant community for many decades. Despite extensive research efforts have been made to design laboratory accelerated

MATRIX RELAXATION AFTER FRACTURE IN A TOUGHENED EPOXY

December 10, 2008
Author(s)
Aaron M. Forster, Cyril Clerici, Donald L. Hunston
An efficient method to increase the Mode I fracture energy of a polymer adhesive is to incorporate a rubbery phase within the glassy matrix. In general, the failure surface of a toughened polymer is characterized by cavitated rubber particles and plastic

Automated Monitoring of Thin Film Properties via Ultrasonics

October 16, 2008
Author(s)
Donald L. Hunston
Non-destructively monitoring of the properties in a thin film or layered material (coatings, adhesives, etc.) is a difficult challenge, and yet there are many instances where this would be useful: fabrication (curing or drying), environmental attack, aging

Limits on Toughening in Structural Adhesives

October 16, 2008
Author(s)
Donald L. Hunston, H Jianmei, R Raghavan, D Hoffman
The addition of a toughener to a thermoset resin, usually an epoxy, can increase the fracture energy by an order of magnitude or more. These materials are two phase systems with small toughener particles in a thermoset matrix. The fracture behavior depends

Mechanisms of Moisture Attack in Adhesive bonds Exposed to High Humidity

July 23, 2008
Author(s)
Kar T. Tan, Christopher C. White, Cyril Clerici, Donald L. Hunston, Bryan D. Vogt, Sushil K. Satija, Joshua E. Goldman, Kristen L. Steffens
Studies have show that certain adhesive joints exhibit a dramatic loss of strength when exposed to humidities above a certain critical value. Although much is know about this effect, questions still exist. This study combines neutron reflectivity

ADHESION TEST METHOD FOR SPRAYED APPLIED FIRE RESISTANT MATERIALS

March 12, 2008
Author(s)
Christopher C. White, Kar T. Tan, Donald L. Hunston
Fire resistive materials are exceptional at providing an effective thermal barrier to structural steel from the heat flux from a fire, provided it is in close proximity to the steel during the fire event. The adhesion of the fire resistive materials is

E-Glass/DGEBA/m-PDA Single Fiber Composites: Interface Debonding During Fiber Fracture

October 1, 2007
Author(s)
Gale A. Holmes, R C. Peterson, Donald L. Hunston, Walter G. McDonough
In this paper, we examine the regions of debonding between the fibers and the matrix surrounding fiber breaks formed during single-fiber fragmentation tests. The materials used were E-glass fibers embedded in a matrix of diglycidyl ether of bisphenol-A

Challenges in Characterizing Sealant

September 14, 2005
Author(s)
Christopher C. White, Donald L. Hunston
Sealant is one of the very few major consumer products valued primarily for its rheological and adhesive properties. While, these materials may appear to be simple elastic solids, upon further examination, their behavior can be extremely complex. In this

Issues Relating to the Mechanical Property Characterization of Sealant

July 1, 2004
Author(s)
Christopher C. White, Donald L. Hunston
fective characterization of the mechanical properties of sealant requires knowledge of the non-linear complex viscoelastic properties. Additionally, all cured sealants, typically elastomeric materials, exhibit the Mullins effect, which also must be

The Effect of Movement During Cure of a Silicone Sealant

March 8, 2004
Author(s)
Christopher C. White, Donald L. Hunston
Movement of the building joint sealant during cure is thought to affect the fully cured mechanical properties. To examine this potential effect, a one-part silicone sealant was cured from 10 h to 168 h after sample creation before the onset of movement

Durability Gap Analysis for Fiber-Reinforced Polymer Composites in Civil Infrastructure

June 18, 2003
Author(s)
V M. Karbhari, Donald L. Hunston, B Benmokrane, T Juska, Roy S. Morgan, J Lesko, U Sorathia, D R. Reynaud
The lack of a comprehensive, validated, and easily accessible data base for the durability of fiber-reinforced polymer _FRP_composites as related to civil infrastructure applications has been identified as a critical barrier to widespread acceptance of