| Matrix-Fiber Stress Transfer in Composite Materials Elasto-Plastic Model with an Interphase Layer |
DEC 87 |
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| Authors:
F. C. Lhotellier; T. C. Ward; H. F. Brinson; VIRGINIA TECH CENTER FOR ADHESION SCIENCE BLACKSBURG
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 | The matrix fiber stress transfer in glass/epoxy composite materials and studied using analytical and experimental methods. The mathematical model that was developed calculates the stress fields in the fiber, interphase, and neighboring matrix near a fiber break. This scheme takes into account the elastic plastic behavior of both the matrix and the interphase and it includes the treatment of stress concentration near the discontinuities of the fibers. The radius of ... |
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| A Finite Element Analysis of Adhesively Bonded Composite Joints Including Geometric Nonlinearity, Nonlinear Viscoelasticity, Moisture Diffusion, and Delayed Failure |
DEC 87 |
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| Authors:
S. Roy; J. N. Reddy; VIRGINIA TECH CENTER FOR ADHESION SCIENCE BLACKSBURG
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| A two-dimensional finite-element computational procedure is developed for the accurate analysis of the strains and stresses in adhesively bonded joints. The large displacements and rotations experienced by the adherends and the adhesive are taken into account by invoking the updated Lagrangian description of motion. The adhesive layer is modeled using Schapery's nonlinear single integral constitutive law for uniaxial and multiaxial states of stress. Effect of temperature and stress level on ... |
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| A Finite Element Analysis of Adhesively Bonded Composite Joints Including Geometric Nonlinearity, Nonlinear Viscoelasticity Moisture Diffusion and Delayed Failure |
OCT 87 |
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| Authors:
S. Roy; J. N. Reddy; VIRGINIA TECH CENTER FOR ADHESION SCIENCE BLACKSBURG
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| A two-dimensional finite-element computational procedure is developed for an analysis of adhesively bonded joints with nonlinear viscoelasticity, moisture diffusion and delayed failure models. Effect of temperature and stress level on the viscoelastic response is taken into account by a nonlinear shift factor definition, and penetrant sorption is accounted via a nonlinear Fickean diffusion model in which the diffusion coefficient is dependent on the penetrant concentration and dilatational strain. A delayed ... |
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| An Interdisciplinary Approach to Predictive Modeling of Structural Adhesive Bonding. Factors Affecting the Durability of Titanium/Epoxy Bonds |
OCT 87 |
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| Authors:
J. A. Filbey; J. P. Wightman; VIRGINIA TECH CENTER FOR ADHESION SCIENCE BLACKSBURG
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| Factors influencing the durability of Titanium-6-4 / epoxy and Ti-6-4 / metal alkoxide / epoxy interphases were studied by first determining chemical and HYSICAL PROPERTIES OF Ti-6-4 adherend surfaces; second by characterizing the strength and durability of Ti-6-4 / epoxy bonds; and third by using aluminum and titanium alkoxides as possible adhesion promoters. Ti-6-4 adherend surfaces were oxidized either by chemical etch or anodization. Four principal pretreatments were studied: chromic ... |
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| Bending of a Bonded Beam as a Test Method for Adhesive Properties |
AUG 87 |
91 pages |
| Authors:
E. Moussiaux; H. F. Brinson; A. H. Cardon; VIRGINIA TECH CENTER FOR ADHESION SCIENCE BLACKSBURG
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 | A strength-of-materials type solution is obtained for the shear stress state in the adhesive layer of a bonded cantilever beam subjected to an end load. The shear stress is constant through the thickness of the adhesive layer and varies from zero at the fixed end to a maximum value at the free end. This maximum value can, under certain conditions, be calculated from knowledge of the load and the beam ... |
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| Durability (Lifetime) Predictions Adhesively Bonded Structures |
21 JUL 1987 |
28 pages |
| Authors:
Hal F. Brinson; VIRGINIA TECH CENTER FOR ADHESION SCIENCE BLACKSBURG
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| A brief review of past and current methods for life time or durability assessment of engineering structures is given. It is noted that adhesively bonded structures exhibit all the features that compromise the durability of metals and polymers plus additional features related to the interface between the adhesive and the adherend. A discussion of current techniques on adhesives is given which includes moisture diffusion, temperature, and other effects. It is ... |
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| An Interdisciplinary Approach to Predictive Modeling of Structural Adhesive Bonding, Chromic Acid Anodized Ti-6Al-4V: Its Characterization and Its Single Lap Bond Strength to Heat Resistant Adhesives |
JUN 87 |
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| Authors:
Jean A. Skiles; J. P. Wightman; VIRGINIA TECH CENTER FOR ADHESION SCIENCE BLACKSBURG
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| Anodized Titanium Aluminum Vanadium adhesive bonds exhibit improved corrosion resistance and a higher strength to weight ratio compared to conventional metal bonding techniques for primary and/or secondary structural applications. This work was conducted to identify chromic acid (CA) anodization and bond process conditions which produced durable, structural applications. This work was conducted to identify chromic acid (CA) anodization and bond process conditions which produced durable, structural anodized Titanium Aluminum Vanadium ... |
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| A Nonlinear Constitutive Behavior for Diffusion in Polymers |
24 FEB 87 |
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| Authors:
D. R. Lefebvre; T. C. Ward; D. A. Dillard; H. F. Brinson; VIRGINIA TECH CENTER FOR ADHESION SCIENCE BLACKSBURG
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| Non-linear diffusion is defined within the framework of Fick's laws where the diffusion coefficient, D, is a function of penetrant concentration, temperature and stress. It is also recognized that these same parameters are contained in a memory dependent free volume description of polymers. Combining the Stokes-Einstein equation for diffusion with a WLF shift function allows the Doolittle equation for free volume to be interpreted in terms of diffusion of penetrant. ... |
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| The Development of a Modified Double Cantilever Beam Specimen for Measuring the Fracture Energy of Rubber to Metal Bonds |
20 NOV 86 |
30 pages |
| Authors:
Didier R. Lefebvre; David A. Dillard; VIRGINIA TECH CENTER FOR ADHESION SCIENCE BLACKSBURG
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| Rubber to metal bonds are important in a variety of automotive, tire, and marine applications. A new technique is discussed for measuring the strain energy release rates of these adhesively bonded joints in the presence of harsh environments. Guidelines for design and applications are given. |
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| Nonlinear Viscoelastic Analysis of Adhesively Bonded Joints |
NOV 86 |
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| Authors:
S. Roy; J. N. Reddy; VIRGINIA TECH CENTER FOR ADHESION SCIENCE BLACKSBURG
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| The report deals with the development of a numerical/computational procedure based on the updated Lagrangian formulation of two-dimensional continuum theory and nonlinear viscoelastic model of Schapery for the stress and deformation analysis of adhesively bonded joints. Schapery's uniaxial, single- integral law for nonlinear viscoelastic behavior is modified for two dimensions and included in the incremental, updated Lagrangian formulation that includes geometric nonlinear effects. The finite element method is used to ... |
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| An Interdisciplinary Approach to Predictive Modeling of Structural Adhesive Bonding. Characterization of Ti-6Al-4V Oxides and the Adhesive/Oxide Interphase |
OCT 86 |
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| Authors:
J. A. Filbey; J. P. Wightman; VIRGINIA TECH CENTER FOR ADHESION SCIENCE BLACKSBURG
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| The hydrothermal durability of adhesive bonds is currently an active area of research. This work focuses on titanium/epoxy bonding using metal alkoxide primers as adhesive promoters. Pike showed that sec-butyl aluminum alkoxide enhances the durability of PAA (phosphoric acid anodized) and FPL (forest Products Lab) etched 2024 aluminum bonded with the wedge test using epoxy adhesives. No variation in bond performance was observed when the cure temperature of the alkoxide ... |
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| An Interdisciplinary Approach to Predictive Modeling of Structural Adhesive Bonding. Characterization of Ti-6Al-4V Oxides and The Adhesive/Oxide Interphase |
AUG 86 |
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| Authors:
J. A. Filbey; J. P. Wightman; VIRGINIA TECH CENTER FOR ADHESION SCIENCE BLACKSBURG
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| Ti-6A1-4V, a high strength, light weight corrosion resistant alloy, possesses many applications for structural adhesive bonding. This report covers the interaction of pretreated surfaces with heat, alkoxide primers, thin polymer films, structural epoxy, and hostile environments. The stability of the oxides at temperatures of 450 C is shown. Alkoxide primers enhance the durability of adhesively bonded aluminum. Characterization of alkoxide primers on Ti-6-4 has begun as well as evaluation of ... |
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| An Interdisciplinary Approach to Predictive Modeling of Structural Adhesive Bonding. Characterization of Ti-6Al-4V Oxides and the Adhesive/Oxide Interphase |
MAY 86 |
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| Authors:
J. A. Filbey; J. P. Wightman; VIRGINIA TECH CENTER FOR ADHESION SCIENCE BLACKSBURG
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| Ti-6-4, being a high strength, lightweight, corrosion resistant alloy, possesses many uses for structural adhesive bonding. Many researchers are therefore finding better pretreatments, characterizing the oxide surface and evaluating bonding performance. The work reported here will encompass both oxide characterization and evaluation of adhesive bonds. The chemical composition of oxides created by specific pretreatments was studied by XPS, AES, SIMS, contact angles, and indicator dyes. The surface topography and structure ... |
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| An Interdisciplinary Approach to Predictive Modeling of Structural Adhesive Bonding Characterization of Chromic Acid and Anodized Ti-6Al-4V and Anodized Ti-6Al-4V Single Lap Bonds to Polyphenylquinoxaline |
JAN 86 |
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| Authors:
Jean A. Skiles; J. P. Wightman; VIRGINIA TECH CENTER FOR ADHESION SCIENCE BLACKSBURG
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| The purpose of this 1985 status report is to describe the: 1. morphology, thickness and structure characterization of chromic acid anodized Ti-6Al-4V determined by Transmission Electron Microscopy (TEM) and Selected Area Electron Diffraction (SAED); 2. unfulled polyphenylquinoxaline (PPQ) - chromic acid anodized (CAA) Ti-6Al-4V unaged single lap bond strength data; 3. unstressed thermal aging tests in progress for PPQ - CAA Ti-6Al-4V single lap bonds, and 4. tests in progress ... |
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Reports by Corporate Author
