Dynamic Fracture Characterization of Small Specimens: A Study of Loading Rate Effects on Acrylic and Acrylic Bone Cement

Abstract

A longbar apparatus for subjecting relatively small samples to stresswave loading has been devised for failure characterization. A methodology based on digital image correlation (DIC) used in conjunction with ultra highspeed photography and a longbar impactor has been developed for determining dynamic crack initiation stress intensity factor (SIF) (KIinid), as well as SIFs for a rapidly growing crack (KId) during highstrain rate events. By altering the material of the pulse shaper, a range of strain rates has been attained. Commercial grade PMMA was first used to calibrate the device, and then dynamic fracture characterization was performed for the first time on PMMAbased bone cement (BC). Despite several key differences, the two materials performed similarly during quasistatic fracture tests; however, under dynamic loading conditions, bone cement exhibited significantly lower crack initiation SIF (KIinid), lower dynamic SIFs (KId), and higher crack tip velocities for three different dynamic loading rates (Kآ·=6.524أ—104 MPam s1).