Feasibility of using a novel instrumented human head surrogate to measure helmet, head and brain kinematics and intracranial pressure during multidirectional impact tests

Abstract

Objectives: Aim of the work is to present the feasibility of using an Instrumented Human Head Surrogate (IHHS-1) during multidirectional impacts while wearing a modern ski helmet. The IHHS-1 is intended to provide reliable and repeatable data for the experimental validation of FE models and for the experimental evaluation of modern helmets designed to enhance the degree of protection against multidirectional impacts. Design: The new IHHS-1 includes 9 triaxial MEMS accelerometers embedded in a silicone rubber brain, independently molded and presenting lobes separation and cerebellum, placed into an ABS skull filled with surrogate cerebrospinal fluid. A triaxial MEMS gyroscope is placed at the brain center of mass. Intracranial pressure can be detected by eight pressure sensors applied to the skull internal surface along a transversal plane located at the brain center of mass and two at the apex. Additional MEMS sensors positioned over the skull and the helmet allow comparison between outer and inner structure kinematics and surrogate CSF pressure behavior. Methods: The IHHS-1 was mounted through a Hybrid III neck on a force platform and impacted with a striker connected to a pendulum tower, with the impact energies reaching 24J. Impact locations were aligned with the brain center of mass and located in the back (sagittal axis), right (90 • from sagittal axis), back/right (45 •), and front right (135 •) locations. Following dynamic data were collected: values of the linear accelerations and angular velocities of the brain, skull and helmet; intracranial pressures inside the skull. Results: Despite the relatively low intensity of impacts (HIC at skull max value 46), the skull rotational actions reached BrIC values of 0.33 and angular accelerations of 5216 rad/s 2 , whereas brain angular acceleration resulted between 1,44 and 2,1 times lower with similar values of BrIC. Conclusions: The IHHS-1 is a physical head surrogate that can produce repeatable data for the interpretation of inner structures behavior during multidirectional impacts with or without helmets of different characteristics.

Examining ski area padding for head and neck injury mitigation

“…As with all testing, our model had limitations including ATD biofidelity and study design. The geometry and stiffness of the Hybrid-III head and neck are different from a live person and biofidelic heads and necks 21,22 that could influence the results. The head and neck rotation in our tests could be dependent on the attachment between the padding and the wooden pole, the friction between the head/helmet and padding, 15 or both.…”

Head and neck injury potential during water sports falls: examining the effects of helmets

“…The larger diameters and irregularities of a live person's head would be expected to increase the effective (total) drag coefficient (C T ) in unhelmeted falls and would reduce the differences between unhelmeted and helmeted tests. While other headforms may be more biofidelic than the Hybrid-III, such as novel human head surrogates [31] or the NOCSAE headforms, their availability or the ability to waterproof the sensors made them too difficult to use in this testing.…”

A Novel Multi-Axial Pressure Sensor Probe for Measuring Triaxial Stress States Inside Soft Materials

“…Indeed, such materials are widely used where high flexibility and strain are required, and their instrumentation represents a challenge that could improve the measurement of the human body and wearable devices. Soft materials such as polydimethylsiloxane (PDMS) or other silicone rubbers are investigated as possible soft tissue surrogates [ 1 , 2 ], and brain surrogates made of these materials are adopted by researchers who are trying to improve the biofidelity of their physical models of the human head [ 3 , 4 , 5 , 6 ]. A biofidelic head model is needed to improve the evaluation of brain kinematics during impacts and, thus, the effectiveness of head protective gear.…”

“…However, despite the number of physical surrogates already developed [ 3 , 4 , 5 , 6 ], finite element (FE) models of the head are still superior in terms of measure capability, as the stress state of tissues is given as a continuous field. On this matter, an estimate of brain strain and stress during dynamic impacts is available only with numerical methods [ 7 , 8 , 9 ] and lacks an experimental counterpart that could validate FE models and improve the comprehension of this phenomena.…”