Compression Test Fixture with Asymmetric Channels

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Solution Overview

Problem

Conventional compression test fixtures are inadequate for testing off-axis composite specimens due to visual obstruction and insufficient spacing, limiting the use of advanced inspection techniques and preventing the testing of specimens with varying dimensions.

Innovation Solution

A compression test fixture with a first and second specimen engagement member having channels of different depths, allowing a gap for visible major surfaces and accommodating sideways expansion, which supports the specimen without causing failure at the ends and enables testing of specimens with varying widths and lengths.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional compression test fixtures with I-shaped members are used to hold the test specimen, then the specimen is supported during compression testing, but the major surfaces of the test specimen are occluded from view, preventing advanced inspection techniques

Engineering Contradiction:

Improvespecimen support stabilityVSAvoidvisibility of major surfaces

Core Design Contradiction:

ReliabilityVSDifficulty of detecting and measuring

Solution Approach 1:

The fixture is divided into separate engagement members (first and second engagement members) that can be positioned independently. This segmentation allows the specimen to be supported at its ends while leaving the major surfaces exposed for inspection, resolving the contradiction between support stability and surface visibility.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention transitions from a conventional sandwich-style fixture to an end-supported fixture configuration. By supporting the specimen at its ends rather than compressing it between two large surfaces, the major surfaces remain accessible for advanced inspection techniques while maintaining compression testing capability.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Reliability

If conventional compression test fixtures are used, then basic compression strain and failure data can be obtained, but the fixtures do not provide enough spacing for axial load application and prevent testing of specimens with varying dimensions

Engineering Contradiction:

Improvecompression data acquisitionVSAvoidspecimen dimension variability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The fixture design with adjustable engagement members and varying channel depths creates a universal testing system that can accommodate specimens of different dimensions. The same fixture configuration can test various specimen sizes while maintaining reliable compression data acquisition, eliminating the need for fixture changes between tests.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The fixture incorporates adjustable elements that can be reconfigured for different specimen dimensions. This dynamic adaptability allows the fixture to maintain proper spacing for axial load application regardless of specimen size, enabling versatile testing while preserving measurement reliability.

Inventive Principle:

Principle #15Dynamics

3Difficulty of detecting and measuring

If the test specimen is held only at the ends rather than sandwiched between fixture members, then the major surfaces remain visible, but the test specimen may fail at the ends and/or buckle

Engineering Contradiction:

Improvevisibility of major surfacesVSAvoidtest validity

Core Design Contradiction:

Difficulty of detecting and measuringVSReliability

Solution Approach 1:

The fixture provides localized support through engagement members positioned at specific locations (ends and intermediate positions) rather than continuous contact. This local quality approach prevents buckling at critical locations while leaving the major surfaces exposed, maintaining both test validity and surface visibility.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Intermediate support elements act as mediators between the end-supported configuration and full sandwich fixation. These intermediary supports prevent end failure and buckling while maintaining the visibility advantage of end-supported fixtures, resolving the contradiction between support adequacy and surface accessibility.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS10578528B2Compression test fixture and method therefor

Publication Date: 2020.03.03 THE BOEING CO

AI summary

A compression test fixture including a first specimen engagement member having a first channel, the first channel having a first depth; a second specimen engagement member having a second channel having a second depth that is different than the first depth; and at least one coupling member engaged to both the first specimen engagement member and the second specimen engagement member such that a gap is defined between the first specimen engagement member and the second specimen engagement member, where the first channel and the second channel support the test specimen within the gap such that at least one opposing major surface of the test specimen is visible within the gap.