PIRHONEN ET AL. 200kV5.04000XBSE99 10vkd2 Figure 5. The SEM image of the observed area. The fiber has been immersed in SBF for 5 weeks. The layers in figure from top to bottom are glass, Si-rich layer, CaP-rich layer, and had formed already after 24 h of immersion and a slight Cap had disintegrated from the surface during sample prep- increase of Ca and P ions could already be detected at this aration time point. After 5 weeks of immersion, the thickness of the There is interest to develop new materials for biomedical ilica layer varied from 5 to 30 um and the inner Cap layer purposes and bioactive glass fibers bring interesting possibi showed a constant thickness of 2 um. Although the Cap ities for example as a reinforcement in polymeric composites content of this sample was initially higher, the outer layers of Thus, the idea of using bioactive glass fibers to reinforce biopolymers is not new, and several research groups have studied this issue. For example, the processing and mechan- ical properties of bioactive or resorbable glass fiber rein- forced composite materials have been reported by Dunn et al (1985), Lin(1986), and Krebs et al. (1993).Marcolongo et al. have also published in vitro and in vivo studies on bioactive glass fiber reinforced polysulfones. They found that bone tissue exhibited direct contact with the glass fibers and strengths significantly higher than with polymer controls ic djacent polymer matrix, resulting in interfacial bo As reinforcement in composites, the fiber strength is the most infuential factor on the strength of the composite. The strength of the glass fiber is dependent on the defect structure, for example, cracks, voids, and impurities of the fiber, and possibly also on the stress state of the fiber. Thinner fibers have a smaller surface area, that is, a smaller probability for the existence of flaws, and this will lead to higher strength values. This may also explain the variation in tensile and 100 um flexural stress values in this study. In the three-point testing. Ovc the area under maximum stress is significantly smaller com- pared with the situation in tensile testing. Figure 6. A SEM image using back scattered electron (BCE)of a fiber The cooling of the glass fiber in melt spinning happens immersed in SBF for 5 weeks. The glass is seen as a light gray, silica rather quickly. This causes stress distribution that affects the as a dark gray, and CaP as a white zone in the image. The black arrow glass fiber, resulting in compression stress in the surface parts shows remnant of a second Cap layer and tensile stress in the inner parts. This toughening phenhad formed already after 24 h of immersion and a slight increase of Ca and P ions could already be detected at this time point. After 5 weeks of immersion, the thickness of the silica layer varied from 5 to 30
m and the inner CaP layer showed a constant thickness of 2
m. Although the CaP content of this sample was initially higher, the outer layers of CaP had disintegrated from the surface during sample prep￾aration. There is interest to develop new materials for biomedical purposes and bioactive glass fibers bring interesting possibil￾ities for example as a reinforcement in polymeric composites. Thus, the idea of using bioactive glass fibers to reinforce biopolymers is not new, and several research groups have studied this issue. For example, the processing and mechan￾ical properties of bioactive or resorbable glass fiber rein￾forced composite materials have been reported by Dunn et al. (1985),17 Lin (1986),18 and Krebs et al. (1993).19 Marcolongo et al. have also published in vitro and in vivo studies on bioactive glass fiber reinforced polysulfones. They found that bone tissue exhibited direct contact with the glass fibers and adjacent polymer matrix, resulting in interfacial bond strengths significantly higher than with polymer controls.20 As reinforcement in composites, the fiber strength is the most influential factor on the strength of the composite. The strength of the glass fiber is dependent on the defect structure, for example, cracks, voids, and impurities of the fiber, and possibly also on the stress state of the fiber.21 Thinner fibers have a smaller surface area, that is, a smaller probability for the existence of flaws, and this will lead to higher strength values. This may also explain the variation in tensile and flexural stress values in this study. In the three-point testing, the area under maximum stress is significantly smaller com￾pared with the situation in tensile testing. The cooling of the glass fiber in melt spinning happens rather quickly. This causes stress distribution that affects the glass fiber, resulting in compression stress in the surface parts and tensile stress in the inner parts. This toughening phenom￾Figure 5. The SEM image of the observed area. The fiber has been immersed in SBF for 5 weeks. The layers in figure from top to bottom are glass, Si-rich layer, CaP-rich layer, and epoxy. Figure 6. A SEM image using back scattered electron (BCE) of a fiber immersed in SBF for 5 weeks. The glass is seen as a light gray, silica as a dark gray, and CaP as a white zone in the image. The black arrow shows remnant of a second CaP layer. 232 PIRHONEN ET AL