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The biofidelity of the Hybrid III headform in impact is largely dependent on local head geometry and viscoelastic mechanical properties of its polymer skin. Accordingly, for accurate simulation of the ATD headform in computational models, a quantitative understanding of the mechanical properties of skin material is required at a variety of strain rates and strain amplitudes. The objective of this study was to characterize the head skin material of the Hybrid III test dummy for finite deformations and at moderate strain rates for blunt impact simulation using finite element models Head skin material from a single ATD was tested using uniaxial compression. A viscoelastic constitutive model with separable temporal and elastic responses was used to characterize the nonlinear and viscoelastic material behavior.

The cervical facet capsular ligaments are thought to be an important anatomical site of whiplash injury, although the mechanism by which these structures may be injured during whiplash remains unclear. The purpose of this study was to quantify the intervertebral flexibility and maximum principal strain in the facet capsular ligament under combined shear, bending and compressive loads similar to those which occur during whiplash loading. Two motion segments (C3-4 and C5-6) from seven female donors (50 ± P 10 years) were exposed to quasi-static posterior shear loads of 135 N applied to the superior vertebra on four occasions while under compressive axial preloads of 0 N, 45 N, 197 N and 325 N. Vertebral body motions and the full Lagrangian strain field in the right facet capsular ligament were measured using stereophotogrammetry. After flexibility testing, the right facet joint of each motion segment was isolated and failed in posterior shear.

Cervical spine behavior for generalized loading is often characterized using a full three-dimensional flexibility matrix. While experimental studies have been aimed at determining cervical motion segment behavior, their accuracy and utility have been limited both experimentally and analytically. For example, the nondiagonal terms, describing coupled motions, of the matrices have often been omitted. Flexibility terms have been primarily represented as constants despite the known nonlinear stiffening response of the spine. Moreover, there is presently no study validating the flexibility approach for predicting vertebral motions; nor have the effects of approximations and simplifications to the matrix representations been quantified. Yet, the flexibility matrix currently forms the basis for all multibody dynamics models of cervical spine motion.