Date of Award

3-2006

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Aeronautics and Astronautics

First Advisor

Anthony N. Palazotto, PhD

Abstract

The purpose of this thesis is to apply a non-commercialized spline-based (BSpline Analysis Method or BSAM) computer program to model and predict strain fields in two composite repairs, a scarf joint and a stepped-lap joint, subjected to static tensile loading. Test specimens with scarf and stepped-lap joints are fabricated using quasiisotropic sixteen ply panels made from IM6/3501-6 prepreg with a [+452/02/-452/902]s lay-up. The panels were bonded together with FM-300M (0.05psf), a 176°C cure film adhesive, under positive pressure. A total of five coupons of each joint type are made. Two of the stepped-lap and scarf coupons are instrumented with acoustic emission sensors and loaded in tension to failure to determine appropriate loading for experimentation. Moire interferometry, a high resolution full-field optical technique used to measure displacements on a surface, is used to acquire experimental strain data. Diffraction grating is applied to the polished edge of two stepped-lap and two scarf coupons, while one coupon of each was selected for experimentation under a static tensile load of 450lbf.
Using measurements from the actual coupon specimens, idealized models of the stepped-lap and scarf joints are developed for the BSAM computer program. For the scarf joint, a linear bond-line and uniform adhesive layer are modeled. In reality, the bond-line was not exactly straight and the adhesive layer varied in thickness across the length of the repair. For the stepped-lap joint, steps with perfectly square corners are modeled; in reality, the bottom of each step was rounded.

AFIT Designator

AFIT-GAE-ENY-06-M09

DTIC Accession Number

ADA459902

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