title: The anisotropic mechanical behaviour of electro-spun biodegradable polymer scaffolds: Experimental characterisation and constitutive formulation.
abstract: Electro-spun biodegradable polymer fibrous structures exhibit anisotropic mechanical properties dependent on the degree of fibre alignment. Degradation and mechanical anisotropy need to be captured in a constitutive formulation when computational modelling is used in the development and design optimisation of such scaffolds. Biodegradable polyester-urethane scaffolds were electro-spun and underwent uniaxial tensile testing in and transverse to the direction of predominant fibre alignment before and after in vitro degradation of up to 28 days. A microstructurally-based transversely isotropic hyperelastic continuum constitutive formulation was developed and its parameters were identified from the experimental stress-strain data of the scaffolds at various stages of degradation. During scaffold degradation, maximum stress and strain in circumferential direction decreased from 1.02 ± 0.23 MPa to 0.38 ± 0.004 MPa and from 46 ± 11 % to 12 ± 2 %, respectively. In longitudinal direction, maximum stress and strain decreased from 0.071 ± 0.016 MPa to 0.010 ± 0.007 MPa and from 69 ± 24 % to 8 ± 2 %, respectively. The constitutive parameters were identified for both directions of the non-degraded and degraded scaffold for strain range varying between 0% and 16% with coefficients of determination r(2)>0.871. The six-parameter constitutive formulation proved versatile enough to capture the varying non-linear transversely isotropic behaviour of the fibrous scaffold throughout various stages of degradation.
authors: National Centre for Advanced Tribology at Southampton (nCATS), Engineering Sciences, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, UK; Bioengineering Science Research Group, Engineering Sciences, Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, UK; Division of Biomedical Engineering, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory 7935, South Africa. Electronic address: g.limbert@soton.ac.uk.
authors: Georges
authors: G
authors: Limbert
authors: Cardiovascular Research Unit, Chris Barnard Department of Cardiothoracic Surgery, Faculty of Health Sciences, University of Cape Town, Observatory 7935, South Africa.
authors: Rodaina
authors: R
authors: Omar
authors: Cardiovascular Research Unit, Chris Barnard Department of Cardiothoracic Surgery, Faculty of Health Sciences, University of Cape Town, Observatory 7935, South Africa.
authors: Hugo
authors: H
authors: Krynauw
authors: Cardiovascular Research Unit, Chris Barnard Department of Cardiothoracic Surgery, Faculty of Health Sciences, University of Cape Town, Observatory 7935, South Africa.
authors: Deon
authors: D
authors: Bezuidenhout
authors: Division of Biomedical Engineering, Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory 7935, South Africa; Centre for Research in Computational and Applied Mechanics, University of Cape Town, Rondebosch 7701, South Africa; Research Office, University of Cape Town, Mowbray 7701, South Africa.
authors: Thomas
authors: T
authors: Franz
mesh_terms: D016880:Anisotropy; D004560:Electricity; D055595:Mechanical Phenomena; D008970:Molecular Weight; D011091:Polyesters / Q000737:chemistry*; D013314:Stress, Mechanical; D054457:Tissue Scaffolds / Q000737:chemistry*; D014520:Urethane / Q000737:chemistry
chemical_list: D011091:Polyesters; D014520:Urethane
keywords: Biodegradable; Constitutive modelling; Electro-spinning; Mechanical properties; Polymer; Transverse isotropy