Mechanical properties and modelling of a hydrophilic composite used as a biomaterial

Artificial ligaments were fabricated by reinforcing a hydrophilic thermoplastic polyurethane matrix with poly-ethyleneterephtalate (PET) fibres, using the filament winding technology. The specimens were then tested in simple tension to measure the mechanical properties of the artificial ligaments. In order to investigate on the effect of technological parameters, three types of windings were manufactured, each type being identified by the winding angle and the fibre volume fraction that were used. Moreover, a certain amount of the PET fibres was plasma-treated before winding, so composite ligaments reinforced with plasma-treated fibres were obtained. All of the artificial ligaments displayed the typical J-shaped stress–strain curve of natural ligaments, the plasma-treated ones mainly exhibiting a smaller toe region. A mathematical model is proposed to predict the mechanical behaviour of the artificial ligaments. The model is able to reproduce the behaviour of the artificial ligaments, especially the ones reinforced with plasma-treated fibres, and can be further used to simulate the behaviour of artificial ligaments subject to a more physiological deformation history, such as the combination of tension and torsion.