A New Device for High-Speed Biaxial Tissue Testing: Application to Traumatic Rupture of the Aorta

A biaxial test device was designed to obtain the material properties of aortic tissue at rates consistent with those seen in automotive impact. Fundamental to the design are four small tissue clamps used to grasp the ends of the tissue sample. The applied load at each clamp is determined using subminiature load cells in conjunction with miniature accelerometers for inertial compensation. Four lightweight carriages serve as mounting points for each clamp. The carriages ride on linear shafts, and are equipped with low-friction bearings. Each carriage is connected to the top of a central drive disk by a rigid link. A fifth carriage, also connected to the drive disk by a rigid link, is attached at the bottom. A pneumatic cylinder attached to the lower carriage initiates rotation of the disk. This produces identical motion of the upper carriages in four directions away from the disk center. Initial slack in a low-stretch, high-strength rope that connects the cylinder to the lower carriage allows the cylinder to achieve the desired test speed before initiating motion in the carriages. Two lasers, focused on the top and bottom surfaces of the tissue samples measure sample thickness throughout a given test.