Interface-driven human brain injury mechanisms in blast exposure: A fluid–structure interaction model

Blast-induced traumatic brain injury (bTBI) presents a significant challenge for military personnel and civilians exposed to explosions. Beyond combat, bTBI can arise from civilian incidents like industrial accidents (chemical-plant or mining blasts), accidental demolition blasts, fireworks factory explosions, and residential gas-leak detonations. The precise mechanisms by which blast waves damage the brain are still developing. Studies suggest that bTBI is primarily an interface-driven injury, where mechanical forces concentrate at anatomical boundaries including gray–white matter junctions, cortical sulci, cerebrospinal fluid (CSF) spaces, and perivascular structures. Recent research has shown that fluid structure interaction (FSI) simulations are instrumental in capturing shock wave transmission through the skull, CSF, and brain tissue, directly informing the design of protective gear. Here, we developed a high-resolution FSI model of the human head with approximately five million elements and detailed anatomical features (sulci, gyri, CSF compartments, vascular structures) to examine these biomechanical interactions. We employed Friedlander waveform to simulate the blast wave, with adjustments for attenuation through the skull and pressure transmission into the CSF and brain, with peak overpressures ranging from 100 to 1000 kPa and durations up to 6 ms. Our findings indicate that local CSF pressures dropping below its vapor pressure (around –90 kPa) can initiate cavitation, particularly within sulcal and ventricular spaces. This cavitation is accompanied by elevated shear stresses at adjacent gray–white matter interfaces, with strain rates exceeding 250 s⁻¹, co-localizing with diffuse axonal injury (DAI) thresholds. Higher overpressures (500 kPa) also induced intraventricular cavitation and elevated periventricular strain rates. Blast orientation significantly influenced injury distribution, lateral blasts resulted in more diffuse stress fields, while frontal blasts localized damage to anterior cortical regions.