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1975
Wednesday, January 1st
12:00 AM

Attenuation Influences in Adhesive Bond Modeling

Joe Rose, Drexel University

Thousand Oaks, CA

12:00 AM

The goal of this work is to examine attenuation effects so that suitable procedures, signal processing techniques, etc., can be used in considering attenuation influences in the adhesive bonding inspection problem. I might point out that we've performed some work under sponsorship of AFOSR, and to date have been reasonably successful in performing ultrasonic inspection of aluminum FM-47 aluminum-type bonds. We' ve also developed some of the physical modelling and computer programming tools that were used in the work being presented. The work associated with the attenuation is sponsored by Roc well under the ARPA/AFML program.

Detection of Hydrothermal Aging in Composite Materials

David H. Kaelble, Rockwell International

Thousand Oaks, CA

12:00 AM

In the title of this paper the term "hydrothermal", meaning separate or combined conditions of high moisture and temperature, is introduced to describe the complex property degradation processes in two graphite-epoxy composites. It became evident in the course of this study that important hydroelastic stresses degrade composite strength in much the same fashion that thermoelastic stresses do. In fact, the study shows that there are complex internal stress effects within the composite, probably concentrated at the fiber-matrix interface, which depend upon the detailed prior history of moisture-temperature exposure .

Fracture Mechanics of Bonded Structures

Nate Tupper, United States Air Force

Thousand Oaks, CA

12:00 AM

I want to talk a little bit this morning about the damage tolerance philosophy of the Air Force as applied to new systems. I'm going to talk particularly about metals and try to indicate those areas where the philosophy that we're applying in our metal structure is equally applicable to both adhesive bonded joints and composite materials, the idea being that the techniques to satisfy the requirements will change and some of the requirements will change, but the philosophy will be the same. The philosophy has to do with beginning to recognize, and I think we now all do, that structure that is manufactured, rolled out the door and put into service is defective at the time it rolls out the door.

Inspection Requirements for Adhesive Bonded Primary Structures

William J. Shelton, United States Air Force

Thousand Oaks, CA

12:00 AM

This paper is concerned with a program that's being sponsored by the Air Force for the purpose of building an adhesive bonded structure. A discussion will be given on some of the problems that we are currently trying to address; what we are doing to solve these problems; and some of the road map programs that will support the Primary Adhesive Bonded Structure Techno logy (PABST) program. This program is under contract with t he McDonald-Douglas Corp., Long Beach.

The objective of this program is to demonstrate and validate t hat by the use of adhesive bonding as the primary joining method that a structure can be fabricated that will be cheaper, lighter i n weight, and reliable. The approach is to review and analyze several design configurations and select a single design for fabrication. To support this decision testing will be accomplished on actual test components representative of the design selected, in addition to extensive coupon testing . After fabrication the structure will be subjected to several life cycle test s at the Air Force Flight Dynamics Laboratory, Wright-Patterson Air Force Base, Ohio

Interfacial Structure and Strength of Adhesive Bonds

Tennyson Smith, Rockwell International

Thousand Oaks, CA

12:00 AM

An adhesive bond is a sandwich structure that has various zones within it as shown in Fig. 1. The physical and chemical properties of these various zones determine the bond strength and the durability of the bond. I hope that I'll be able to shed some light on the real properties of the interface rather than schematic properties as shown in Fig. 1 and relate the physical and chemical properties to the resultant bond strength. I will, therefore, discuss something about the oxide, the topography of the surface after it's been prepared for bonding , the thickness of the oxide, the interface , the primer and the adhesive in an actual fracture surface. The dotted line in Fig. 1 represents a hypothetical fracture line and, in fact, we find that failure does occur in all of these regions designated by the dashed line. The bond fails as the weakest regions fail.

Methods Development for Non-Destructive Measurement of Bond Strength in Adhesively Bonded Structures

James A. Seydel, University of Michigan - Ann Arbor

Thousand Oaks, CA

12:00 AM

While reasonably satisfactory methods exist for nondestructively determining t he presence or absence of an adhesive bond, no method exists for nondestructively determining the strength of what appears to be a good bond. Bonds that do not attain their full strength can be caused by a thin layer of contaminant , improper surface roughness, and a variety of other surface phenomena that are difficult to detect by conventional methods.l,2,3 One technique is to use an ultrasonic pulse to investigate the bond interface. Since the amplitude of the pulse reflected by t he bond interface is a f unction of the elastic properties of the bond, i t should be possible to correlate t he absolute ultrasonic reflectivity with t he bond strength.

Ultrasonic Wave Interactions with Interfaces

George Alders, Rockwell International
Lloyd Graham, Rockwell International

Thousand Oaks, CA

12:00 AM

The objective of the work that I will describe was to determine experimentally how a sound wave interacts with a layer whose thickness is measured in atomic sized units. That is, the interface layers are measured in hundreds of angstroms and are thus much, much thinner than any of the millimeter or tenths of millimeter kinds of wave lengths that we ordinarily have, or can hope to have to interrogate the bond line.

The question we must address is; How does a very long wave length ultrasonic wave interact with a very thin layer or collection of layers? Or; When we get a signal back from an interface, how should we unfold it to learn something about the nature of the interface?