Biomimetic composite structure to simulate tendon performance

Abstract

The objective of this study is to design a composite that mimics the mechanical performance of a tendon. The biomimetic composite structure was composed of an elastomeric matrix reinforced with continuous polymer fibers. The matrix material was a thermoplastic polyurethane, Estane 5714 F5P. A polyamide (Nylon 6-6), a polyethylene terephthalate (Dacron) and a block copolymer of polyethylene oxide and aromatic polyurethane (Lycra) were used as the straight fiber reinforcement A crimped Nylon 6 fiber was obtained in order to simulate the crimp in natural tendon.

The composites were manufactured with the polymer matrix in solution form. A solution of the polyurethane and tetrahydrofuran was used to coat the fibers using a single-tow coating device. The effect of structure of the composite on the mechanical properties was examined by manufacturing composites with three different structures: straight fiber reinforced, crimped fiber reinforced and braided composites.

The composites were then examined for physical and mechanical properties. All of the composites exceeded the natural tendon's breaking strength and elongation to failure. Through biomimicking, a composite was manufactured with a higher initial stiffness and strength than the crimped nylon fiber. The shape of the stress-strain curves of tendon and the synthetic composites were also compared.

The scale of the structure of the composites was compared to that of tendon. A non-dimensional ratio of the periodicity of the crimp to filament size (R) revealed a much larger level of structure in the synthetic composites than in the tendon. This ratio was found to have a correlation to the mechanical properties of the composites.