Novel uses of carbon composites for the fabrication of external fixators

A novel bone fractures external fixator has been developed by using carbon fibre reinforced epoxy resin components. Aim of the project was the design and fabrication of an external fixator lighter than metallic ones, X-rays transparent, with suitable mechanical properties, and sufficiently stable under vapour sterilization conditions. The hydrothermal stability of carbon fibre epoxy resin composites has been assessed by measuring the elastic and ultimate properties of a properly selected carbon fibre-epoxy resin system after prolonged simulated sterilization treatments in water at 120 °C. The suitability of filament winding as a technique appropriate to produce the tubular elements of the designed fixator has been investigated by determining the relationship between winding angle and required mechanical properties of the tubes. Filament wounded composite tubes have been obtained using a high tenacity PAN based carbon fibre and a DGEBA epoxy resin cross-linked by an anhydride based curing agent. Winding angles have been changed in the range from ±5° to 90°. The axial tensile modulus of composite tubes can be reasonably well predicted on the basis of the lamination theory, while the most promising among the analyzed failure criteria in terms of fitting with the experimental axial tensile strength data, seemed to be the Tsai-Wu criterion.