A.R. Boccaccini et al. /Journal of Materials Processing Technology 169(2005)270-280 4. Conclusions The system sapphire fibre reinforced borosilicate glass matrix composite was studied aiming at developing"optome- chanical composites". Different techniques of fabrication were used: randomly orientated chopped fibre reinforced Imperial College composites were fabricated by pressureless sintering, unidirectionally oriented fibre reinforced composites were fabricated by hot-pressing and by sandwiching two slides London of glass and an array of parallel fibres(sandwich structure composites) Pressureless sintered samples were porous, specially near the fibre/matrix interfaces and there was poor contact between the fibres and the matrix Hot-pressed and"sandwich struc ture"composites were dense and showed a strong interface between fibres and matrix. Interface engineering should be introduced by coating the fibres with a suitable material(e.g SnO2)in order to obtain a weaker interface and improve toughness by inducing significant fibre pull-out effect. Pressureless sintered and hot-pressed samples were due to residual ever, the hot-pressed unreinforced matrix was translucent. On the other hand," sandwich structure"composites were transparent and showed significant light transmittance in the mper visible wavelength range, only 20% lower than that of the n unreinforced matrix(borosilicate glass slides). These results indicate that this technique of fabrication is viable for pro- duction of"optomechanical composites"with borosilicate 0 mm glass matrix. The samples fabricated, which exhibit strong fibre/matrix interface bonding, represent an improved(but less cost-effective) version of the traditional fire and impact es qualitatively demonstrating the transparency of the samples. The images resistant material wired glass. The composites should there how that it is possible to see through the composites. The under-laying text fore be interesting materials for high performance fire resis- remains clearly legible if the sample is placed (a)in direct contact with th tant windows, requiring high impact strength and avoidance text and(b )even if the composite is not directly above the tex of fragmentation upon fracture, obviously in cases where stringent requirements may justify the higher costs of the Acknowledgments Experimental assistance of Mr. Norbert Galy is appre- d-b ciated. ARB acknowledges financial support of the Royal Society, London, UK(Grant nr. 574006G503 References 350400450 600650700750800 [I.w. Donald, Review. Methods for improving the mechanical prop erties of oxide glasses, J. Mater. Sci. 24(1989)4177-4208 [2]KM. Prewo, J.J. Brennan, G K. Layden, Fiber reinforced glasse 12. Results of the measurements of light transmittance of selected san and glass-ceramics for high performance applications, Ceram. Bull the UV and visible wavelength ranges: hot-pressed sample without 65(1986)305-322 fibres(a), "sandwich structure" sample without fibres(b) and"sandwich 3R. D. Rawlings, Glass-ceramic matrix composites, Composites 25 structuresample with fibres, before and after polishing(c and d, respec 994)372-379 tively). For the composites, light transmittance was measured perpendicu- 14 A.R. Boccaccini, Glass and glass-ceramic matrix composite materi- larly to the fibre axes. als: a review, J. Ceram Soc. Jpn. 109(7)(2001)S99-0S10A.R. Boccaccini et al. / Journal of Materials Processing Technology 169 (2005) 270–280 279 Fig. 11. Macroscopic appearance of polished “sandwich structure” compos￾ites qualitatively demonstrating the transparency of the samples. The images show that it is possible to see through the composites. The under-laying text remains clearly legible if the sample is placed (a) in direct contact with the text and (b) even if the composite is not directly above the text. Fig. 12. Results of the measurements of light transmittance of selected sam￾ples in the UV and visible wavelength ranges: hot-pressed sample without fibres (a), “sandwich structure” sample without fibres (b) and “sandwich structure” sample with fibres, before and after polishing (c and d, respec￾tively). For the composites, light transmittance was measured perpendicu￾larly to the fibre axes. 4. Conclusions The system sapphire fibre reinforced borosilicate glass matrix composite was studied aiming at developing “optome￾chanical composites”. Different techniques of fabrication were used: randomly orientated chopped fibre reinforced composites were fabricated by pressureless sintering, unidirectionally oriented fibre reinforced composites were fabricated by hot-pressing and by sandwiching two slides of glass and an array of parallel fibres (sandwich structure composites). Pressureless sintered samples were porous, specially near the fibre/matrix interfaces and there was poor contact between the fibres and the matrix. Hot-pressed and “sandwich struc￾ture” composites were dense and showed a strong interface between fibres and matrix. Interface engineering should be introduced by coating the fibres with a suitable material (e.g. SnO2) in order to obtain a weaker interface and improve toughness by inducing significant fibre pull-out effect. Pressureless sintered and hot-pressed samples were opaque due to residual porosity and sintering defects. How￾ever, the hot-pressed unreinforced matrix was translucent. On the other hand, “sandwich structure” composites were transparent and showed significant light transmittance in the visible wavelength range, only 20% lower than that of the unreinforced matrix (borosilicate glass slides). These results indicate that this technique of fabrication is viable for pro￾duction of “optomechanical composites” with borosilicate glass matrix. The samples fabricated, which exhibit strong fibre/matrix interface bonding, represent an improved (but less cost-effective) version of the traditional fire and impact resistant material wired glass. The composites should there￾fore be interesting materials for high performance fire resis￾tant windows, requiring high impact strength and avoidance of fragmentation upon fracture, obviously in cases where stringent requirements may justify the higher costs of the material. Acknowledgments Experimental assistance of Mr. Norbert Galy is appre￾ciated. ARB acknowledges financial support of the Royal Society, London, UK (Grant nr. 574006.G503). References [1] I.W. Donald, Review. Methods for improving the mechanical prop￾erties of oxide glasses, J. Mater. Sci. 24 (1989) 4177–4208. [2] K.M. Prewo, J.J. Brennan, G.K. Layden, Fiber reinforced glasses and glass-ceramics for high performance applications, Ceram. Bull. 65 (1986) 305–322. [3] R.D. Rawlings, Glass-ceramic matrix composites, Composites 25 (1994) 372–379. [4] A.R. Boccaccini, Glass and glass-ceramic matrix composite materi￾als: a review, J. Ceram. Soc.Jpn. 109 (7) (2001) S99–0S109