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- ItemBorosilicate glass matrix composites reinforced with short metal fibres(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Boccaccini, Aldo R.; Ondracek, Gerhard; Syhre, ClaudiaThe reinforcement of a borosihcate glass with Hastelloy X short fibres is discussed. A fabrication process consisting of wet mixing of the glass powder and the metallic fibres and hot pressing of the mixtures was developed. Composites containing 15 vol.% fibres homogeneously distributed in a near fully dense glass matrix were obtained. Both Young's modulus and fracture strength increased with increasing volume fraction of fibres. The experimental values for the Young's modulus are in agreement with theoretical predictions. No fibre pull-out during fracture was detected and there is a good interfacial bond. By means of a rule-of-mixture calculation for the fracture energy, a five-fold increase in fracture toughness for composites containing 15 vol.% fibres can be predicted.
- ItemBehaviour of a commercial wired glass under low energy ballistic impact(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2004) Atiq, Shabbar; Rawlings, Rees D.; Boccaccini, Aldo R.Α study of the ballistic impact resistance of a commercial wired glass has been undertaken using a gas gun capable of velocities up to 400 m s-1. The projectile was a steel ball and impact energies up to 7.32 J were used. The extent of the impact damage was assessed by the mass of ejected material, the area of the Hertzian cone left by the impact and residual strength. Crack morphologies similar to those reported in monolithic glasses were observed, namely ring, cone and radial cracks. The impact energy dependencies of the mass of ejected material and cone area were similar showing a rapid increase at energies above about 4.35 J. In contrast, the residual strength remained at 20 % or less of the as received wired glass irrespective of impact energy. This was attributed to the wire mesh remaining intact for the ballistic impact conditions investigated.
- ItemCarbon-fibre reinforced glass matrix composites: self-lubricating materials for wear applications in vacuum(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2001) Boccaccini, Aldo R.; Gevorkian, GevorkThe self-lubricating wear behaviour of a C-fibre reinforced borosilicate glass matrix composite in vacuum was investigated by using a rotating pump experimental facility. The vanes were made of the composite material and the stator of the pump was of cast iron. Glass composite wear was accompanied by material transfer onto the stator surface. The formation of isle-type and continuous graphitic films on the counter-body surface was observed. The continuous film provided adequate lubrication during friction, leading to a relatively low wear rate of the composite for the conditions investigated.
- ItemPreparation and characterization of a glass matrix composite containing aluminium titanate particles with improved thermal shock resistance(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1999) Boccaccini, Aldo R.; Pfeiffer, KerstinImproving the thermal shock resistance of sintered glasses is an important task to broaden their technical and structural applications. In this study, the incorporation of second phase particles with low Young's modulus (E) into glass matrices to form composite materials is shown to be a convenient approach to increase their thermal shock resistance. Novel aluminosilicate glass matrix composites containing aluminium titanate (Al₂TiO₅) particles were fabricated by powder technology and pressureless sintering. By incorporating up to 30 vol.% of aluminium titanate particles a nearly fourfold increase of the thermal shock resistance was achieved. This was determined by measuring the critical temperature difference necessary to cause superficial cracks in cylindrical samples subjected to water-quench tests. The experimental results are shown to confirm qualitatively the theoretical prediction of the model of Hasselman et al. for the thermal shock resistance of low-E'/high-E composites.
- ItemSintered glass-ceramic matrix composites made from Latvian silicate wastes(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2002) Rozenstrauha, Ineta; Cimdins, Rudolfs; Berzina, Liga; Bajare, Diana; Bossert, Jörg; Boccaccini, Aldo R.Powder technology and sintering were used to fabricate glass-ceramic matrix composites from Latvian industrial wastes and alumina platelets reinforcement. The optimization of the sintering behaviour of glass-ceramic compositions containing clay and alumina platelets was carried out. Highly crystalline and dense products (> 90 % theoretical density) were fabricated by sintering at temperatures in the range 1040 to 1060 °C, depending on composition. Addition of waste glass to influence the sintering temperature and sintering interval was also investigated. Composites showed higher fracture strength (up to 97 MPa) and hardness than unreinforced glass-ceramics. The "best" composition in terms of density and mechanical properties contained 20 wt% alumina platelets. The matrix exhibited a microstructure composed mainly of elongated crystals of pyroxene type in a residual glassy matrix. These composites are candidates for applications as building materials, such as floor and wall tiles, and for manufacturing machine elements and parts.
- ItemMechanical behaviour and environmental stability of continuous fibre-reinforced glass-ceramic matrix composites(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1996) West, Grant; Taplin, David M. R.; Boccaccini, Aldo R.; Plucknett, Kevin; Lewis, Mike H.The mechanical behaviour of three continuous Silicon carbide fibre-reinforced glass-ceramic matrix composites has been investigated at room and high temperatures. Commercially available composites with magnesium aluminosilicate, calcium aluminosilicate and barium magnesium aluminosilicate glass-ceramic matrices were considered. The materials were tested in the as-received and aged (heat-treated in a n oxidizing environment) condition. Four-point bend static tests and fiexural creep, fatigue and creep-fatigue tests were carried out a s well as a small quantity of tensile tests of aged composites. The experimental results have highlighted the importance of the carbon-rich layer at the fibre/matrix interface for obtaining "graceful" failures. At temperatures of 700 to 800 °C oxidative degradation of the interface results in significant strength reduction and a transition to brittle fracture mode. By rapid heat treatment of the materials at 1100°C for 1 h it is possible to seal the fibre ends by forming a silica "plug" which prevents oxygen ingress, retaining the carbon-rich interphase and composite behaviour. The results of the creep and creep-fatigue tests indicate low-cycle loading has a strong influence on the life of components at high temperatures.