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Image-based high strain rate testing of orthopaedic bone cement

Image-based high strain rate testing of orthopaedic bone cement
Image-based high strain rate testing of orthopaedic bone cement

Bone cement is widely used for the fixation of orthopaedic implants. It is a multi-component material that consists of a PMMA base with a small proportion of (usually ceramic) radiopacifier to enable the cement to be observed by X-ray. Bone cement is formed through an exothermic reaction in which a powder of pre-polymerised beads of PMMA reacts with MMA monomer. The resulting polymer microstructure consists of PMMA beads in a matrix of newly formed PMMA containing radiopacifier particles. In service, bone cement can experience deformation over a range of strain rates, from the lower end in normal gait to 100s of s-1 in the case of falls or impacts. In the current study, it is hypothesised that the response of homogeneous (clear) PMMA to high strain rates will be different to that of bone cement due to the microstructural differences. There have been very few studies on this topic in the past, mostly because of the difficulty involved in adapting the Hopkinson bar protocol to this material, particularly for dynamic tension. The objective of this paper is to present new results on the stiffness and damping of bone cement at strain rates in the range of 100 s-1, and to compare the data with that obtained on clear PMMA. The technique employed here to measure the mechanical properties of both commercial grade PMMA and bone cement is a new image-based DMTA method recently proposed by Seghir and Pierron (Seghir, Pierron, Exp. Mech., 2018). This allows for the measurement of the complex modulus over a range of temperatures and strain rates (100s of s-1). The method relies on imaging the deformation of the specimen bearing a printed grid using a Shimadzu HPV-X camera at up to 5 million frames per second. This allows for the time-resolved displacements to be measured, leading to fields of strain and acceleration, the latter being used to derive stress information to build up stress-strain curves. The methodology is described in more details in www.photodyn.org.

EDP Sciences
Fletcher, Lloyd
48dca64b-f93c-4655-9205-eaf4e74be90c
Regal, Xavier
d71a76b1-09f8-46b4-abb3-d8070f56bf05
Seghir, Rian
cd6555fb-7c90-46e2-b16a-1a6f0a666e59
Pierron, Fabrice
a1fb4a70-6f34-4625-bc23-fcb6996b79b4
Browne, Martin
6578cc37-7bd6-43b9-ae5c-77ccb7726397
Fletcher, Lloyd
48dca64b-f93c-4655-9205-eaf4e74be90c
Regal, Xavier
d71a76b1-09f8-46b4-abb3-d8070f56bf05
Seghir, Rian
cd6555fb-7c90-46e2-b16a-1a6f0a666e59
Pierron, Fabrice
a1fb4a70-6f34-4625-bc23-fcb6996b79b4
Browne, Martin
6578cc37-7bd6-43b9-ae5c-77ccb7726397

Fletcher, Lloyd, Regal, Xavier, Seghir, Rian, Pierron, Fabrice and Browne, Martin (2018) Image-based high strain rate testing of orthopaedic bone cement. In DYMAT 2018 - 12th International Conference on the Mechanical and Physical Behaviour of Materials under Dynamic Loading. vol. 183, EDP Sciences.. (doi:10.1051/epjconf/201818304014).

Record type: Conference or Workshop Item (Paper)

Abstract

Bone cement is widely used for the fixation of orthopaedic implants. It is a multi-component material that consists of a PMMA base with a small proportion of (usually ceramic) radiopacifier to enable the cement to be observed by X-ray. Bone cement is formed through an exothermic reaction in which a powder of pre-polymerised beads of PMMA reacts with MMA monomer. The resulting polymer microstructure consists of PMMA beads in a matrix of newly formed PMMA containing radiopacifier particles. In service, bone cement can experience deformation over a range of strain rates, from the lower end in normal gait to 100s of s-1 in the case of falls or impacts. In the current study, it is hypothesised that the response of homogeneous (clear) PMMA to high strain rates will be different to that of bone cement due to the microstructural differences. There have been very few studies on this topic in the past, mostly because of the difficulty involved in adapting the Hopkinson bar protocol to this material, particularly for dynamic tension. The objective of this paper is to present new results on the stiffness and damping of bone cement at strain rates in the range of 100 s-1, and to compare the data with that obtained on clear PMMA. The technique employed here to measure the mechanical properties of both commercial grade PMMA and bone cement is a new image-based DMTA method recently proposed by Seghir and Pierron (Seghir, Pierron, Exp. Mech., 2018). This allows for the measurement of the complex modulus over a range of temperatures and strain rates (100s of s-1). The method relies on imaging the deformation of the specimen bearing a printed grid using a Shimadzu HPV-X camera at up to 5 million frames per second. This allows for the time-resolved displacements to be measured, leading to fields of strain and acceleration, the latter being used to derive stress information to build up stress-strain curves. The methodology is described in more details in www.photodyn.org.

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e-pub ahead of print date: 7 September 2018
Venue - Dates: 12th International Conference on the Mechanical and Physical Behaviour of Materials under Dynamic Loading, DYMAT 2018, Arcachon, France, 2018-09-09 - 2018-09-14

Identifiers

Local EPrints ID: 423807
URI: http://eprints.soton.ac.uk/id/eprint/423807
PURE UUID: 14c76738-3fa8-4e09-8157-1b940c54fe53
ORCID for Fabrice Pierron: ORCID iD orcid.org/0000-0003-2813-4994
ORCID for Martin Browne: ORCID iD orcid.org/0000-0001-5184-050X

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Date deposited: 02 Oct 2018 16:30
Last modified: 20 Jul 2019 01:17

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Contributors

Author: Lloyd Fletcher
Author: Xavier Regal
Author: Rian Seghir
Author: Fabrice Pierron ORCID iD
Author: Martin Browne ORCID iD

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