The double cantilever beam test applied to mode I fracture characterization of cortical bone tissue

Abstract

Compliance Fracture toughness Modeling A B S T R A C TThe primary objective of this work was to analyse the adequacy of the Double Cantilever Beam (DCB) test in determining fracture toughness under pure mode I loading of cortical bone tissue. A new data reduction scheme based on specimen compliance and the crack equivalent concept was used to overcome the difficulties inherent in crack monitoring during its growth. It provides a complete resistance curve, which is fundamental in estimating the fracture energy. A cohesive zone model was used to simulate damage initiation and propagation, thus assessing the efficacy of the proposed testing method and data reduction scheme. Subsequently, the DCB test was applied to evaluate the mode I fracture energy of hydrated and thermally dehydrated cortical bone tissue from young bovine femur, in the tangential-longitudinal propagation system. The results obtained demonstrate the efficacy of the DCB test and the proposed data reduction scheme on the bone fracture characterization under mode I loading.

Bone fracture characterization using the end notched flexure test

“…The initial crack length a 0 is formed by a notch (0.3 mm thick) fabricated with a circular saw and a natural short crack with 0.25 mm nominal length, executed using a sharp blade. This procedure avoids unwanted blunt cracks which cause a spurious increase of fracture energy at crack initiation (visible in the R-curve) as observed by Morais et al [4]. In order to induce stable crack propagation, the initial crack had a length a 0 equal to 70% of the specimen half-length L [10], which means that a nominal value of a 0 =21 mm was considered.…”

“…Elastic properties of bovine cortical bone [4,14]. During crack growth the current compliance C is used to estimate an equivalent crack length a e through Eqs.…”

“…Fracture studies found in the literature are predominantly dedicated to mode I fracture [1][2][3][4]. However, a considerable number of fractures in bone are induced by shear loading, which occurs during torsion and twisting efforts.…”

Fracture characterization of human cortical bone under mode II loading using the end-notched flexure test

“…In the last decade there have been several works dedicated to fracture behavior of bone namely development of finite element-based models to predict bone fracture [5]. The large majority is about fracture characterization under mode I loading [7][8][9]23]. However, during daily activities of humans shear fractures are prone to occur.…”

Dynamic Properties of Cortical Bone Tissue: Impact Tests and Numerical Study

“…From mechanics of materials point of view, some previous numerical models were developed using a homogenization theory to predict macroscopic behaviour of cortical bone tissue [14,15]. Also, a recent study [16] demonstrated adequacy of a Double-Cantilever Beam (DCB) test for determining fracture toughness under pure mode I loading of cortical bone by implementing a new data reduction scheme based on specimen compliance. Despite this body of research, experimental and numerical studies of the dynamic behaviour of a cortical bone tissue attracted less attention.…”