The development of a modified biaxial composite test specimen
type: CreativeWork
description: Bi-axial testing of composite structures has been an important topic in the research community for some years now. Bi-axial test specimens in the past have typically been cruciform specimens with a tapered thickness gage section. This ensures that the specimen will fail under bi-axial loading rather than uni-axial loading due to high stress concentrations at the intersecting loading arms. To reduce the stress concentration in the loading arms the intersection points are rounded and curved inward toward the center of the specimen. By having the curvature of the intersecting arms come closer into the specimen it reduces the amount of uni-axial stress at that point. In order to reduce the stress even more, tapered thickness gage section milling is required to achieve adequate bi-axial failure. In the proposed research these specimens will be modified so that no milling of the gage section is required. The process of milling the gage section of the composite laminate could inflict initial damage to the specimen which would yield inaccurate results. The modified bi-axial specimen will instead have aluminum shims bonded to the rounded corner to ensure bi-axial failure. The location of the shims was determined using Finite Element Analyses which verified the location and magnitude of the stress concentrations. The use of the aluminum shims could allow the cruciform specimen to be completely unscathed of any initial damage. The specimens are thick woven carbon fiber/epoxy bi-axial specimens which previously havent been tested before. Two types of geometries were fabricated, one out of IM7/UF3352 and one out of IM7/PATZ materials, both with a [(0/90)]s lay-up. The first geometry had the aluminum shims. The second configuration consisted of a smaller composite laminate sandwiched in between two pre-fabricated G10 glass/epoxy panels and only machining away the G10 material, keeping the composite laminate unscathed. Both geometries had tapered thickness gage section counterpart…
abstract: Bi-axial testing of composite structures has been an important topic in the research community for some years now. Bi-axial test specimens in the past have typically been cruciform specimens with a tapered thickness gage section. This ensures that the specimen will fail under bi-axial loading rather than uni-axial loading due to high stress concentrations at the intersecting loading arms. To reduce the stress concentration in the loading arms the intersection points are rounded and curved inward toward the center of the specimen. By having the curvature of the intersecting arms come closer into the specimen it reduces the amount of uni-axial stress at that point. In order to reduce the stress even more, tapered thickness gage section milling is required to achieve adequate bi-axial failure. In the proposed research these specimens will be modified so that no milling of the gage section is required. The process of milling the gage section of the composite laminate could inflict initial damage to the specimen which would yield inaccurate results. The modified bi-axial specimen will instead have aluminum shims bonded to the rounded corner to ensure bi-axial failure. The location of the shims was determined using Finite Element Analyses which verified the location and magnitude of the stress concentrations. The use of the aluminum shims could allow the cruciform specimen to be completely unscathed of any initial damage. The specimens are thick woven carbon fiber/epoxy bi-axial specimens which previously havent been tested before. Two types of geometries were fabricated, one out of IM7/UF3352 and one out of IM7/PATZ materials, both with a [(0/90)]s lay-up. The first geometry had the aluminum shims. The second configuration consisted of a smaller composite laminate sandwiched in between two pre-fabricated G10 glass/epoxy panels and only machining away the G10 material, keeping the composite laminate unscathed. Both geometries had tapered thickness gage section counterpart…
author: Torres, Anthony
language: English
keywords: Fibrous composites--Testing, Materials--Dynamic testing, Finite element method.
date published: 2010-09-10T07:00:00Z
date modified: 2026-07-24T05:26:55Z
provider: University of New Mexico
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of New Mexico

PropertyValue
property ID: Handle
value: http://hdl.handle.net/1928/11179