Abstract: A system and method for designing a helmet to reduce mild traumatic brain injury sustained by a user during primary or secondary head impact include modeling a helmeted head including a head, brain, and helmet using a finite element computer model, the finite element computer model including material properties for the head, brain structures, and helmet and estimating at least intracranial pressure, brain strain and strain rate in response to an impact; and selecting at least one of a helmet cushion material and helmet shell material to limit at least one of intracranial pressure, brain strain and strain rate to a corresponding threshold for an associated impact.

Abstract: A system and method for designing a helmet to reduce mild traumatic brain injury sustained by a user during primary or secondary head impact include modeling a helmeted head including a head, brain, and helmet using a finite element computer model, the finite element computer model including material properties for the head, brain structures, and helmet and estimating at least intracranial pressure, brain strain and strain rate in response to an impact; and selecting at least one of a helmet cushion material and helmet shell material to limit at least one of intracranial pressure, brain strain and strain rate to a corresponding threshold for an associated impact.

Abstract: Protective headgear includes an outer shell rotatable relative to an inner shell via a thin layer of elastically and/or plastically yielding material disposed between and secured to the inner and outer shells. The yielding material deforms continuously but non-linearly at least in the tangential or shear direction to mitigate angular acceleration of the head during an impact. The yielding material prevents the inner and outer shells from separating or stopping suddenly to avoid imparting a large angular acceleration to the head. In one embodiment, a protective helmet includes an outer shell secured to an inner shell by a yielding material that elastically deforms continuously but non-linearly when subjected to an angular acceleration below a first threshold and plastically deforms when subjected to an angular acceleration above the first threshold.