Percorrer por autor "Mitchell, G. R."
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- Direct writing of conductive polymer tracks as part of an additive manufacturing processPublication . Mitchell, G. R.; Davis, Fred J.The use of electrically conductive polymers to construct hetereogenous structures via additive manufacturing is an attractive possibility. It maintains the all polymeric nature of such structures. In this work we discuss how this might be achieved in practical additive manufacturing equipment.
- Numerical Thermal Analysis of a T Jump System Used for Studying Polymer BehaviourPublication . Gomes, S.; Pascoal-Faria, P.; Mitchell, G. R.; Gkourmpis, T.; Youngs, T.The processing of polymers is highly complex. The study of their crystallisation assumes an important role and needs to be carefully detailed. Scattering experiments can be used to study polymer molecular organisation. However these procedures are still very multifaceted leading to the need for planning all the details in the experiments that are to be performed. This manuscript presents a finite element model developed to study the temperature variation of a T Jump System, which has been used for studying polymer behaviour with the NIMROD instrument at the ISIS Neutron and Muon Source, UK. Results show that the variation across the sample was 2ºC at a maximum temperature of 70ºC and 1ºC at a maximum temperature of 50ºC.
- Structure development during additive manufacturingPublication . Tojeira, A.; Biscaia, S.; Viana, T.; Bártolo, P. J.; Mitchell, G. R.Additive manufacturing involves the shaping of a product through the use of a liquid phase which is subsequently transformed to the solid state by cooling or through the use of chemical cross-linking reactions. Of particular note is the fused deposition modeling which utilizes semi-crystalline polymers such as poly(ε-caprolactone) or poly(lactic acid) and has been employed in CDRsp to prepare highly porous scaffolds for Tissue Engineering. We show that the crystallization process amplifies small levels of molecular anisotropy introduced in the additive writing process. We show that the level of anisotropy is significantly dependent on the process parameters such as temperature, write speed, and flow rate. The differences in the crystalline morphology introduced by changing these process parameters will have a marked impact on the mechanical properties. This in turn will alter the growth of tissue on such scaffold structures. As with other polymer processing procedures, tuning the process parameters provides a route to controlling and defining the structure and morphology of the scaffold and the properties exhibited by that scaffold.