MOTIVATION: Warrior Web

Warrior Web system in need of compression element that:
• 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 SOLUTION: Racquet Design

• The racquet design was the first solution
– Capable of achieving the desired loads
– Too rigid to perform all of the necessary tasks
- Uncomfortable
• It was a promising initial design
– The compression column would need to be smaller and capable of becoming more flexible

EULER BUCKLING OF COLUMNS

• If a higher mode of buckling is reached
– The critical buckling load increases by a factor of n2
– The size of the column may be significantly reduced
• This higher mode of buckling may be induced using hard constraints
– Hard continuous constraints (Figure 2)
– Hoop tension cords (that would hold the column against the torso, the spacing depicted in Figure 1)
– Some combination of the two

SYSTEM SCHEMATIC

Relevant dimensions
• Constraint inner thickness
• Constraint inner width
• Column width
• Column thickness
• Buckling modal wavelength
• Displacement imposed on column

THEORETICAL SOLUTION FOR NON-FLOATING CONSTRAINT

What we expect to see:

TESTING

Initial goal: Describe how the column reacts within one continuous floating constraint
• A series of tests have been performed to try and better understand the nature of the column within a single floating constraint
-Different hang ups have been encountered with being able to image the shape of the column for thinner gaps

TESTING INFO

• 4 constraint lengths were tested 12” 6” 4” and 2”
• 4 constraint gaps were tested: 0” .044” .088” and .132”
• Gap from bottom and top 1/8”
• 0/90/0 t700 .5” wide column (measured thickness .023”)
– I chose the 3 ply because there would be less bending resistance, and higher modes will be attainable (it also should be able to carry the loads we are concerned with)
• Column lubricated with WD40
• Videos taken of all tests

RESULTS

PATH FORWARD: Segmented Constraints

• Once the single constraint has been figured out and properly described
– The sizes of the available columns may be narrowed down
- The smallest gap provides the necessary response for the column
• The system will need to be more flexible
– Segmented constraints is one solution

Goal: Determine the ideal length for the constraints

PATHFORWARD: Hoop Tension Constraints

• Incorporate hoop tension constraints to combat global buckling of the system

Goal: Determine the best orientation and number of hoop tension constraints that allow for necessary flexibility when unloaded and compressive capabilities when loaded

ACKNOWLEDGEMENTS

This work is sponsored by DARPA under award number W911QX-12-C-0042
This work is supported by the University of Delaware Mechanical Engineering Department Center for Composite Materials and advisors Dr. John Gillespie and Dr. Shridhar Yarlagadda

Special thanks: Dr. Nicolas Schevshenko, Shashank Sharma, Dr. John Tierney, Tom Cender, John Gangloff, Rick Readdy, Philip Rollins, Philip Roach, Corinne Hamed, Penny O’Donnell, Robin Mack, Michael Yeager, Matthew Walter, Hatice Sas, Chad Philips, Dave Roseman, and many more.