CTEPrevent: Reducing Concussion & CTE Risk Through Advanced Helmet Liner Design
A multi-layer energy-damping helmet liner combining laser-cut PETG honeycomb lattice, polycarbonate, and graded foam layers — validated through FEA simulation and physical impact testing.
Andrew Scarnavack, Arjun Kulkarni, Jackson Cole — Department of Materials Engineering, College of Engineering
Problem
Repeated head impacts in football — including sub-concussive hits — are strongly linked to long-term brain injuries like CTE. Current helmets are good at reducing linear acceleration but poor at reducing rotational acceleration, which drives the large pressure gradients in brain tissue that cause injury.
Existing limitations include lab tests that don't reflect real game impacts, materials that degrade over time, and rotational forces that remain under-addressed. We set out to design a next-gen internal helmet liner that tackles both linear and rotational acceleration by shifting from simply “absorbing hits” to actively controlling energy dissipation and rotation.
Multi-Layer Design
Each layer serves a specific energy management role. The system was iterated through ANSYS simulation and physical prototyping until the layered configuration outperformed current NFL outer helmet liners.
Polycarbonate Shell
1/8"Rigid outer layer — distributes impact load across a wider area
PETG Honeycomb Lattice
3/4"Laser-cut hexagonal lattice — dissipates force through controlled deformation
Silicone Foam
3/4"High-stiffness foam — best safety score (23.6), optimal balance of absorption and compression
EVA Foam
1/4"Mid-range foam — moderate energy absorption, cushioning transition layer
Polyurethane Foam
3/4"Soft inner foam — highest raw energy absorption (~43 kJ), contacts the head
Prototype Materials
PETG Honeycomb Lattice
Laser-cut hexagonal structure for controlled deformation and force dissipation.
Polycarbonate Shell
Rigid outer layer that distributes impact across a wider area before it reaches the foams.
Silicone Foam
Highest stiffness foam — achieved the best safety score of 23.6 in testing.
Polyurethane + EVA Foam
Inner foam layers — polyurethane absorbs the most energy (~43 kJ), EVA provides mid-range cushioning.
Assembled Prototype (Top View)
All layers bonded and labeled for ASTM D1037 drop testing at 75 J impact energy.
Assembled Prototype (Side View)
Cross-section showing distinct layer boundaries — PC, PETG lattice, silicone, EVA, and polyurethane.
Method
Simulation (ANSYS Mechanical)
Layered helmet model: PC shell + PETG lattice + foam stack
Impact conditions: ~1000 J at ~20 m/s
Metrics: linear acceleration, angular acceleration, energy absorption
Realistic material stiffnesses: 22–480 kPa range
Modeled energy absorption by plugging displacement, velocity, and force into kinematic and energy equations
Physical Testing (ASTM D1037)
Tested PC reference first for maximum energy resistance baseline
Built adjustable stand for controlled deformation and shock absorption measurement
Re-tested each layer combination at increasing impact energies (up to 100 J)
3 official runs per helmet, 1 run of PC at 30 J as control
Calculated displacement, velocity, force, and energy absorption from high-speed data
Key Findings
68.7%
Material stiffness influence on safety performance
23.6
Best safety score — Silicone foam optimal configuration
43 kJ
Peak energy absorbed by polyurethane layer
234 kPa
Optimal Young's Modulus (silicone-type)
Energy Absorption ≠ Safety
Polyurethane absorbed the most raw energy (~43 kJ) but had the worst safety score due to excessive compression. Higher stiffness foams like silicone performed better overall.
Stiffness Dominates Performance
Material stiffness accounted for 68.7% of influence on safety outcomes. The optimal configuration used a silicone-type foam at 234 kPa Young's Modulus, 43mm thickness, 321 kg/m³ density.
Results by Material
| Material | Energy Absorbed | Safety Score | Notes |
|---|---|---|---|
| Silicone Foam | ~14 kJ | 23.6 (Best) | Best balance — lowest stress + compression |
| EVA Foam | ~8.3 J | Moderate | Middle performance — good cushioning layer |
| Polyurethane Foam | ~43 kJ | Worst | Highest absorption but excessive compression |
Tools & Materials
Simulation software, testing standards, and prototyping materials
Conclusions
Higher-stiffness foams perform best in simulation — the optimal helmet liner system is PC → PETG → Silicone → EVA → PC.
Our prototype absorbs more energy than the outer helmet liner of current NFL helmets — a promising direction for next-generation head protection.
Future work includes better adhesive bonding between foam layers, thicker and smaller hexagons in the PETG lattice, a blunter drop-test object for realism, and pneumatic rigs for rotational testing.
Limitations & Future Work
Conditions tested are not identical to real football impacts
The data collected is representative of general impact and energy absorption but further implementation into a real helmet geometry with real-impact conditions would be necessary for definitive results. Future iterations would benefit from smaller PETG hexagon sizes, improved inter-layer adhesion, and pneumatic testing rigs for rotational force measurement.