Variation in flexural properties of photo-pultruded composite archwires: analyses of round and rectangular profiles |
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| Authors: | D W Fallis R P Kusy |
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| Affiliation: | (1) Department of Orthodontics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599–7455, USA;(2) Department of Biomedical Engineering, Curriculum in Applied and Material Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599–7455, USA |
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| Abstract: | Prototype continuous, unidirectional, fiber-reinforced composite archwires were manufactured into round and rectangular profiles utilizing a photo-pultrusion process. Both 0.022 inch (0.56 mm) diameter and 0.021 × 0.028 inch (0.53 × 0.71 mm) rectangular composites were formed utilizing commercially available S2-glass® reinforcement within a polymeric matrix. Reinforcement was varied according to the number, denier and twists per inch (TPI) of four S2-glass® yarns to volume levels of 32–74% for round and 41–61% for rectangular profiles. Cross-sectional geometry was evaluated via light microscopy to determine loading characteristics; whereas two flexural properties (the elastic moduli and flexural strengths) were determined by 3-point bending tests. Morphological evaluation of samples revealed that as the TPI increased from 1 to 8, the yarns were more separated from one another and distributed more peripherally within a profile. For round and rectangular profiles utilizing 1 TPI fibers, moduli increased with fiber content approaching theoretical values. For round profiles utilizing 1 TPI and 4 TPI fibers, flexural strengths increased until the loading geometry was optimized. In contrast, the flexural strengths of composites that were pultruded with 8 TPI fibers were not improved at any loading level. Doubling the denier of the yarn, without altering the loading, increased both the moduli and flexural strengths in rectangular samples; whereas, the increases observed in round samples were not statistically significant. At optimal loading the maximum mean moduli and strengths equaled 53.6 ± 2.0 and 1.36 ± 0.17 (GPa) for round wire and equaled 45.7 ± 0.8 and 1.40 ± 0.05 (GPa) for rectangular wires, respectively. These moduli were midway between that of martensitic NiTi (33.4 GPa) and beta-titanium (72.4 GPa), and produced about one-quarter the force of a stainless steel wire per unit of activation. Values of strengths placed this composite material in the range of published values for beta-titanium wires (1.3–1.5 GPa). © 2000 Kluwer Academic Publishers |
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