Characterisation and modelling of continuous electrospun poly(ɛ- caprolactone) filaments for biological tissue repair

This study investigates the mechanical behaviour of poly($\varepsilon$-caprolactone) (PCL) continuous filaments produced by a novel electrospinning (ES) method. These filaments can be processed into woven or braided structures, showing great promises as scaffolds for ligament and tendon repair. Mechanical characterisation of the filaments using DMA and uniaxial tensile tests shows that the filament response is viscoelastic–viscoplastic. Filaments tested using bollard grips present an initially linear elastic response, followed by plastic yielding with two-stage hardening. The filaments are highly stretchable, reaching more than 1000% strain. The different deformation stages are correlated to the evolution of the micro-fibre network observed using SEM, involving the untangling, alignment and stretching of the fibres. A large deformation viscoelastic–viscoplastic model is proposed, which successfully captures the mechanical response of the filaments under non-monotonic loading conditions. Our study also highlights the sensitivity of the measured mechanical response to the type of mechanical grips, namely bollard or screw-side grips.