In-Fiber Bragg Grating Impact Force Transducer for Studying Head–Helmet Mechanical Interaction in Head Impact

Abstract

In this paper, we present the first Bragg-grating-based transducer system for application to trauma biomechanics, more specifically head-helmet contact force measurements secondary to headform impact. The transducer comprises an aluminum superstructure designed to withstand typical impact forces in helmeted impact and to have resonances that allow the overall sensor system to capture all relevant spectral components of force transients in impact. Structural finite-element models and strain-optic relationships are used to predict transducer sensitivity to impact force as well as mechanical resonances. The model predictions are verified through experimental calibration, and calibration results are, on average, within 10% of model predictions of force sensitivity. The model predicted first mechanical resonance is 72 kHz. The impact force transducer is also validated for helmeted impacts using an industry standard impact experiment and test headform. Results indicate excellent repeatability: maximum standard deviation of force measurements of 0.4% of the net force applied to the impacted headform and average error in the time duration of the force transients of only 4%. Transient impact forces measured with the Bragg grating transducer are in agreement with magnitudes inferred from work of previous researchers. The presented transducer can be applied with both helmet test and anthropomorphic headforms to measure distributions of transient forces and therefore hypotheses related to helmet performance and head injury.Index Terms-Bragg grating, concussion, force transducer, head injury, helmet, impact force, mild brain injury, optical fibre, skull fracture.

A Fiber-Optic Sensor-Embedded and Machine Learning Assisted Smart Helmet for Multi-Variable Blunt Force Impact Sensing in Real Time

“…The randomized selection of data records for training and testing is vital for an accurate representation of the parent database—and all of its intrinsic characteristics— in both sets. The 7–25% split in the parent database was chosen because previous studies [ 17 , 18 , 19 ] reported that such a split is able to ensure proper training of the ML models. The data split is also useful for testing the prediction accuracy of the models in a rigorous manner.…”

“…Owing to its unique advantages, such as light weight, small size, high flexibility, etc., the fiber optic sensor can be embedded into the helmet without influencing the functionality of the structure [ 10 , 11 ]. As one of the widely applied fiber optic sensors, the fiber Bragg grating (FBG) has attracted many interests for sensing applications such as strain [ 12 , 13 ], vibration [ 14 , 15 ], and impact [ 16 , 17 , 18 ]. Compared with other types of widely used single-point fiber optic sensors, such as fiber optic interferometers [ 19 , 20 , 21 , 22 ] and long-period fiber gratings [ 23 , 24 ], FBG has a simple and robust in-line structure.…”

“…Butz and Dennison developed an in-fiber grating impact force transducer, which allowed the overall sensor system to capture all relevant spectral components of force transients from impacts for studying head-helmet mechanical interactions from head impacts. The transducer showed good repeatability in validation experiments [ 18 ].…”

A Test Bed to Examine Helmet Fit and Retention and Biomechanical Measures of Head and Neck Injury in Simulated Impact

“…Arrange five fit sensors on the skin of the headform, positioned on the front, back, left, right and top (Figure 2). NOTE: The sensors are a modified version of Bragg grating force transducers developed within the research group 19,20,21,22 , optimized to measure fit forces over a range of 0 to 50 N. The modified sensors have a thickness and diameter of 2.6 mm and 14 mm respectively. 2.…”

Strain Modal Analysis of Small and Light Pipes Using Distributed Fibre Bragg Grating Sensors

“…Unlike conventional electrical techniques, Fibre Bragg Grating (FBG) sensors adopt light as a sensing signal, which gives FBG sensors various attractive characteristics, such as small size, light weight, immunity to electromagnetic interference, and large multiplexing capability [7,8,9]. In recent years, FBG sensors have been investigated and applied for dynamic strain measurement and modal analysis [10,11,12,13].…”