Center for Composite Materials - University of Delaware

Research Summary

Rapid Prototyping of Advanced Passive Dynamic Ankle-Foot Orthoses (PD-AFO) Designs for Wounded Warriors

Authors: Prof. John W. Gillespie Jr., Dr. S. Yarlagadda, Dr. J. Tierney, Center for Composite Materials, UD

Program Objective

- Develop integrated design and manufacturing toolchain to enable rapid prototyping of composite Passive Dynamic – Ankle Foot Orthosis (PD-AFO)
-- Rapid turnaround – 24 hrs is Objective
- Majority of combat wounds are extremity injuries
--- 26% are fractures, evenly divided between upper and lower extremities
--- Surgical advancements leading to limb salvage and rehab
--- PD-AFOs – rehab and enable soldier return to duty

- Unique aspects of PD-AFOs
Every one is different (individual customization)
-- PD-AFO requirements change over time for same individual during rehab (tunable properties)
-- Ideally needs very low profile (shoe wearable around it)
-- Soldier loads high (high performance demands)
-- Extreme durability (soldiers break anything…)
-- Rapid turn around (can’t wait weeks to begin rehab)

Program Schematic

Proposed Approach (Two Phases)

- Establish integrated toolset combining geometry, design, analysis and manufacturing (including tooling)
-- Commercial tools already combine geometry, design and analysis
-- Proposed effort will integrate manufacturing and cost models for a variety of composite manufacturing processes
- Exercise toolset to generate library of parametric PD-AFO component models
-- Allows orthotist to match patient needs to AFO concept and establish parameters using biomechanics basis for prescription
-- Selected PD-AFO includes complete manufacturing specification
- Additive Manufacturing for Rapid Custom Tooling
- Downselect optimal manufacturing process (es) for composite PD-AFO
- Process implementation and validation at CCM (Phase 2)
- Demonstrate complete methodology with composite PD-AFO build and evaluation (Phase 2)

Parametric AFO Model

Composite AFO Design

- Orthotist prescribes desired ankle response in AFO based on Patient assessment
-- Example below shows case where linear stiffness may be needed to recover function – more general case will be non-linear (on-going work)


Manufacturing/Tooling

Composite AFO Performance

- Static and Dynamic Performance
-- Develop M-N (moment-cycles) curves for AFOs
--- Initial assessment on 3D printed Polymer AFOs
--- Several generations for carbon fiber AFOs
---- Develop curves from 1st percentile to 99th percentile
- Goal – to demonstrate 1 million cycle durability (~3 years of walking)
- Patient trials leveraged through BADER

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