Analysing the High Strain Rate Behaviour of Cortical Bone with the Image-Based Inertial Impact (IBII) Test

Area of Science:

• Biomechanics
• Materials Science
• Orthopedics

Background:

• Traumatic bone fractures are often caused by high strain rate loading.
• Limited high strain rate data exists for cortical bone, especially in tension.
• Existing split-Hopkinson bar (SHB) methods are challenging for tensile testing of quasi-brittle materials like bone.

Purpose of the Study:

• To apply the Image-Based Inertial Impact (IBII) test to obtain novel high strain rate data for cortical bone.
• To determine the orthotropic stiffness components and tensile failure stress of cortical bone under high strain rates.
• To investigate the rate sensitivity of cortical bone's mechanical properties.

Main Methods:

• Utilized the Image-Based Inertial Impact (IBII) test for high strain rate material analysis.
• Tested bovine cortical bone samples parallel (longitudinal) and perpendicular (transverse) to the long axis.
• Acquired data on elastic stiffness, tensile failure stress, and shear modulus.

Main Results:

• Average longitudinal stiffness: 26 GPa at 1150 s⁻¹; transverse stiffness: 15.2 GPa at 1300 s⁻¹.
• Longitudinal samples showed 22% rate sensitivity; transverse samples showed 5.5% rate sensitivity.
• Average tensile failure stress: 146 MPa (longitudinal) and 53.6 MPa (transverse) at 5200 s⁻¹.
• Average shear modulus: 6.9 GPa at 1200 s⁻¹.

Conclusions:

• The IBII test successfully generated high strain rate orthotropic mechanical data for cortical bone.
• Cortical bone exhibits significant rate sensitivity in its stiffness and failure properties.
• This study provides valuable data for biomechanical modeling and understanding bone fracture mechanisms under dynamic loading.