Center for Composite Materials - University of Delaware

Research Summary

Design of Flexible Bilateral Floating Constraint and Buckling Column

Authors: A. Vanarelli (MSME), J. Gillespie (Ph.D), and S. Yarlagadda (Ph.D)

Introduction and Motivation

Warrior Web program specific design constraints
• Can carry a specified load (soldiers carry from 50 to 150lbs)
• Can be integrated into a garment
• Must be as low profile as possible (weight, Geometry, etc.)
• Must have the capability to be loaded and unloaded based on the wearers needs
• Needs to have enough flexibility so it allows wearer to perform their required tasks

Initial Design

• The buckling column consists of a thin composite column suspended between lateral constraints which induce higher modes of buckling (shown to the right)
• Relevant geometric variables include
- Constraint inner gap
- Constraint inner width
- Column width and thickness
- Constraint and column length

Background

• In past studies the loaded of the buckling column has caused it to experience a repeating series of loading patterns, initial buckling, point contact, line contact, mode transition
• The shape, moment, and shear of the region between contact lengths can be predicted (chai 1998) and those predictions are graphed below

Modeling in Abaqus

• Initial goal: Make a model that accurately predicts the tests under different loading conditions and geometries
• A series of models were made starting with simple. They validated with known values and were made with increase complexity making justifiable assumptions for the unknown
• Below shows the loading of the single precision 12” floating constraint column

Testing

A series of tests were performed varying different parameters
• Constraint and column length
• Constraint gap
• Loading speed
These tests were performed with video captured in parallel to measure important lengths

Analysis

• The shape of the column is shown at different loads with the areas of minimum moment indicated in red (each shape indicated on the load displacement graph to the right)
• The design is too rigid, this information can help find where is best to segment the constraint to increase its flexibility without greatly effecting its loaded

Comparison

• Below shows the difference between the simulation and the actual testing for 12” floating constraint .088” gap system

Path Forward

• Use the lessons learned to ascertain and fix remaining problem with the model
• Use the information found from the modeling to predict the loading of a variety of orientations and where to segment the constraint

Acknowledgements

This work is supported by the Defense Advanced Research Projects Agency under the Warrior Web program under award number W911QX-12-C-0042, The University of Delaware Mechanical Engineering Program, Center for Composite Materials, and advisors Dr. John Gillespie and Dr. Shridhar Yarlagadda

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