Effect of loading rate on the apparent fracture toughness of acrylic bone cement

In this study, a determination is made of the effect of loading rate, v (0.1 mm min(-1) versus 1.0 mm min(-1) versus 10 mm min(-1)) on the value of the plane strain fracture toughness, K(Ic), of three commercial formulations of acrylic bone cement (Osteopal), CMW3, and Copal), that are characterized as "low-", "medium-", and "high-" viscosity brands, respectively). For all formulations, K(Ic) increases with increase in v. However, while this trend is statistically significant for CMW3 and Copal, this is not so for Osteopal. The CMW3 and Copal results are explained in terms of changes of the molecular relaxation transitions in the cement and the thermal state at the crack tip of the test specimen. Two implications of the findings are discussed. In the case of Osteopal, a recommendation for further study is made.