title: Mechanical characterization of brain tissue in tension at dynamic strain rates.
abstract: Mechanical characterization of brain tissue at high loading velocities is crucial for modeling Traumatic Brain Injury (TBI). During severe impact conditions, brain tissue experiences compression, tension and shear. Limited experimental data is available for brain tissue in extension at dynamic strain rates. In this research, a High Rate Tension Device (HRTD) was developed to obtain dynamic properties of brain tissue in extension at strain rates of ≤90/s. In vitro tensile tests were performed to obtain properties of brain tissue at strain rates of 30, 60 and 90/s up to 30% strain. The brain tissue showed a stiffer response with increasing strain rates, showing that hyperelastic models are not adequate. Specifically, the tensile engineering stress at 30% strain was 3.1±0.49kPa, 4.3±0.86kPa, 6.5±0.76kPa (mean±SD) at strain rates of 30, 60 and 90/s, respectively. Force relaxation tests in tension were also conducted at different strain magnitudes (10-60% strain) with the average rise time of 24ms, which were used to derive time dependent parameters. One-term Ogden, Fung and Gent models were used to obtain material parameters from the experimental data. Numerical simulations were performed using a one-term Ogden model to analyze hyperelastic behavior of brain tissue up to 30% strain. The material parameters obtained in this study will help to develop biofidelic human brain finite element models, which can subsequently be used to predict brain injuries under impact conditions and as a reconstruction and simulation tool for forensic investigations.
authors.affiliation: School of Mechanical and Materials Engineering, University College Dublin, Belfield, Dublin 4, Ireland. Electronic address: Badar.Rashid@ucdconnect.ie.
authors.forename: Badar
authors.initials: B
authors.lastname: Rashid
authors.affiliation: School of Mathematics, Statistics and Applied Mathematics, National University of Ireland Galway, Galway, Ireland; School of Mechanical and Materials Engineering, University College Dublin, Belfield, Dublin 4, Ireland. Electronic address: michel.destrade@nuigalway.ie.
authors.forename: Michel
authors.initials: M
authors.lastname: Destrade
authors.affiliation: School of Mechanical and Materials Engineering, University College Dublin, Belfield, Dublin 4, Ireland. Electronic address: michael.gilchrist@ucd.ie.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Gilchrist
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001921:Brain / Q000166:cytology*; D055119:Elastic Modulus; D020342:Finite Element Analysis; D008422:Materials Testing; D017711:Nonlinear Dynamics; D013314:Stress, Mechanical; D013552:Swine; D014783:Viscosity
keywords: Axonal; Dynamic; Impact; Ogden; TBI; Traumatic brain injury