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Specimen Geometry Inducing Fatigue in the Measurement Zone of Composite Fatigue Test Specimens

A composite material, geometry technology, used in the preparation of test samples, the use of repetitive force/pulsation force to test the strength of materials, and the analysis of materials, etc., can solve problems such as failure of the measurement area

Active Publication Date: 2016-08-10
THE BOEING CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0006] A test specimen geometry is required that causes failure of the measurement zone in composite test specimens

Method used

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  • Specimen Geometry Inducing Fatigue in the Measurement Zone of Composite Fatigue Test Specimens
  • Specimen Geometry Inducing Fatigue in the Measurement Zone of Composite Fatigue Test Specimens
  • Specimen Geometry Inducing Fatigue in the Measurement Zone of Composite Fatigue Test Specimens

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Embodiment Construction

[0024] The test specimen geometry disclosed herein has particular application in the field of fatigue testing of scratched composite specimens. Composite scratch tests were conducted to determine the adverse effects of various scratch depths on composite test samples comprising layups of multiple layers, each layer comprising fiber reinforced plastic. Adjacent plies differ in fiber direction to provide increased strength and stiffness to the final laminate. The composite layup specimens can be cut using a water jet programmed to the desired specimen geometry. Each specimen includes first and second load application regions at opposite ends of the specimen, where the sheets are to be bonded, and a relatively narrow intermediate section of reduced cross-section (hereinafter referred to as the "measurement region"), which Designed to promote failure in the middle region of the specimen. Each load application area will have a pair of sheets glued to its ends. The sheet facilita...

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Abstract

A specimen geometry to determine failure in a measurement zone (20) of the specimen during a fatigue test. The propensity to fail in the measurement zone (20) is given by using a bow-tie-shaped test piece (10) coupled with a similarly shaped sheet. The test specimen (10) has a bow-tie-shaped profile with tapered sides that converge as it extends from opposite ends of the specimen to the measurement zone (20), forming a pair of trapezoidal sections connected by the measurement zone (20) (16 and 18) (one is the mirror image of the other). These trapezoidal sections (16 and 18) of the sample (10) comprise areas where similar trapezoidal sheets will be attached to the front and back of the sample. The test specimen (10) has a minimum width and constant thickness in the measurement zone (20) and the height of the measurement zone (20) is not more than 3% of the height of the test specimen (10).

Description

technical field [0001] The present invention relates to the geometry of test specimens used in materials testing. Background technique [0002] In materials science, fatigue is the gradual and localized structural damage that occurs when a material is subjected to cyclic loading, that is, upon repeated loading and unloading. If the load is above a certain threshold, microscopic cracks will start to form at stress concentrations. Eventually the crack will reach a critical size and the structure will break. Since the shape of the structure results in stress concentrations at the microscopic level, it significantly affects the fatigue life of the material. [0003] With the recent and rapid adoption of composite materials in aerospace structures, composites testing has received sufficient attention and scrutiny. Fatigue testing of composite material specimens is of particular interest, as satisfactory test methods for accurately determining the fatigue behavior of composite ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N1/28G01N3/32
CPCG01L5/0095G01N2203/0246G01N3/60G01N2203/0073G01N3/08G01N3/02
Inventor M·J·李N·C·金博尔
Owner THE BOEING CO