# Enhancing Tangential Impact Protection in Helmets: A Numerical and Experimental Evaluation of the O-DAMP System with Shear Thickening Fluids

Daniel Colombo, Nicolas Bailly, Giuseppe La Fauci, Maria Federica Parisi, Martino Colonna

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Daniel Colombo, Nicolas Bailly, Giuseppe La Fauci, Maria Federica Parisi, Martino Colonna. Enhancing Tangential Impact Protection in Helmets: A Numerical and Experimental Evaluation of the O-DAMP System with Shear Thickening Fluids. Multidisciplinary Biomechanics Journal, 2025, 50th congress of the., 10.46298/mbj.16149. hal-05191701v2

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# Enhancing Tangential Impact Protection in Helmets:
A Numerical and Experimental Evaluation of the
O-DAMP System with Shear Thickening Fluids

Daniel Colombo<sup>a*</sup>, Nicolas Bailly<sup>b</sup>, Giuseppe La Fauci<sup>a</sup>,
Maria Federica Parisi<sup>a</sup>, Martino Colonna<sup>a</sup>

<sup>a</sup> Sport Technology Lab, University of Bologna Bologna, Italy

<sup>b</sup> LBA, Marseille, France

* Corresponding author: daniel.colombo2@unibo.it

Received date: 06/04/2025

Accepted date: 27/06/2025

Publication date: 27/10/2025

**Keywords:** helmet, rotational acceleration, non newtonian fluid, finite element method, impact test

© 2025 The Authors
Licence CC-BY 4.0
Published by Société de Biomécanique

## 1. Introduction

Rotational accelerations resulting from oblique impacts are widely recognized as a primary cause of traumatic brain injuries (TBI) (Bourdet, Deck, Tinard, & Willinger, 2011) in motorcyclists. Unlike linear accelerations, which are effectively mitigated by traditional energy-absorbing liners, rotational forces induce shear stresses within the brain, contributing to diffuse axonal injuries and concussions. Despite recent updates in safety standards, helmet designs still struggle to protect against such dynamic loading conditions.

To address this gap, O-DAMP was developed as an innovative anti-rotational system aimed at reducing the transmission of tangential accelerations to the head. O-DAMP is both the commercial name of the product and the name of a university spin-off based at the University of Bologna. The technology is protected by an Italian patent, currently undergoing international extension in Europe and the United States. A second patent application is currently pending. The system exploits non-Newtonian shear thickening fluids to dissipate energy and mitigate brain injury risk.

Unlike existing commercial solutions, which are typically optimized for the velocity ranges defined by regulatory tests, O-DAMP leverages non-Newtonian fluid-based dampers to adaptively dissipate energy across a wide range of impact conditions. This distinctive feature provides enhanced rotational protection even in off-normative scenarios, marking a significant advancement over current state-of-the-art systems.

<figure><img src="image_3.png" /><figcaption>**Figure 1.** Operating principle of the O-DAMP system and its main components</figcaption></figure>

## 2. Methods

The numerical campaign was carried out using the explicit solver Radioss, replicating tangential impact conditions defined by the ECE 22.06 regulation. The study followed a stepwise approach, progressively increasing model complexity while maintaining connection with previous experimental data.

Initial simulations on helmet segments, impacted at 7.5 m/s, were used to calibrate material behavior and contact interactions among internal components, the anvil, and striker. This configuration was transferred to a full-helmet model without O-DAMP and validated against experiments.

The focus then shifted to the non-Newtonian fluid in the O-DAMP system. Sub-models simulated the rheological response of single damper elements. To support
the calibration process, a dedicated test procedure
was developed to compare tangential force transmis-
sion across various fluids. Experimental force-time and
displacement curves enabled matching the numerical
model with physical energy dissipation.

After defining helmet and damping components,
the complete O-DAMP-equipped helmet model was
subjected to tangential impact simulations. Particular
attention was given to the integration of damping units,
their mechanical coupling with surrounding materials,
and dynamic interactions during impacts. Boundary
conditions and contact algorithms matched the validated
experimental setup.

3. Results and Discussion

Experimental impact tests, conducted at a certified lab-
oratory, compared the baseline helmet with prototypes
equipped with O-DAMP technology. The inclusion of
the system resulted in a 17.1% reduction in the Brain
Injury Criterion (BrIC), a 7.9% decrease in the Peak
Rotational Acceleration (PRA), and a 12.5% reduction
in peak angular velocity. These values will serve as ref-
erence targets for validating the numerical simulations,
allowing a direct comparison between standard and
O-DAMP-equipped configurations.

Simulations without O-DAMP showed high fidelity
with experimental responses, supporting the accuracy of
calibration and contact definitions. The fluid sub-models
reproduced expected energy dissipation mechanisms
under dynamic loading.

The simulation framework enables a deeper under-
standing of how internal components contribute
to energy absorption under oblique loading. Local
deformation patterns, stress distributions, and interac-
tion forces typically inaccessible through experiments
can now be assessed with high spatial and temporal
resolution.

This environment also provides a reliable platform
for design analysis and parameter optimization based
on validated results.

4. Conclusions

O-DAMP demonstrated clear potential in reducing
rotational injury metrics in certified experimental tests,
and the numerical environment successfully replicated
these trends. The developed simulation protocol sup-
ports ongoing validation and future design optimization
efforts.

Conflict of Interest Statement

None.

Contributor Roles

Daniel Colombo: corresponding author, experimen-
tal and numerical analysis; Nicolas Bailly: numerical
Analysis; Giuseppe La Fauci: experimental Analysis;
Maria Federica Parisi: material caracterization; Martino
Colonna: material caracterization.

Data, software, code availability

Altair Hyperworks, Radioss.

References

La Fauci, G., Parisi, M., Nanni, A., Crosetta, L.,
Pugno, N. M., & Colonna, M. (2023). Design and
proof-of-concept of an advanced protective sys-
tem for the dissipation of tangential impact energy
in helmets, based on non-Newtonian fluids. *Smart
Materials and Structures*, 32(4), 044004. https://doi.
org/10.1088/1361-665X/acc148

Bourdet, N., Deck, C., Tinard, V., & Willinger, R. (2011). Behaviour of helmets during head impact in real accident cases of motorcyclists. *International Journal of Crashworthiness*, 16(6), 661–670. https://doi.org/10.1080/13588265.2011.613328