MATERIALS CIENCE EIEERIG ELSEVIE Materials Science and Engineering A 417(2006)341-347 www.elsevier.com/locate/msea Mechanical properties of oxide-fiber reinforced glass matrix composites with Bn or SnO2 interfaces D Raab,K. Pfeifer D. Hulsenberg, A R bo occaccin o,* a Technische Universitat ILmenau, Institut fiir Werkstoftechnik, Gustav-Kirchhof-Str 6, D-98693 iLmenau, germany Imperial College London, Department of Materials, Prince Consort Road, London SW7 2BP U Received in revised form 28 October 2005; accepted 3 November 2005 Abstract With the aim of developing optomechanical inorganic materials, boron nitride- coated Nextel M 440 fibers and tin oxide-coated Zen TronM glass fibers were used for manufacturing continuous and short fiber reinforced borosilicate glass matrix composites. No evident loss in tensile strength occurred for the BN-coated Nextel M fibers whereas coating the Zen TronM fiber with tin oxide caused a significant strength decrease Composites with <12 vol% of short or continuous fibers were fabricated by a standard slurry infiltration and hot-pressing process. The mechanical properties of the composites were investigated by uni-and biaxial flexural strength tests. Nextel M 440 short fiber reinforced composites with boron nitride interfaces demonstratedquasi-ductile fracture behaviour under biaxial stress loading with biaxial fracture strength values of up to 88 MPa. The boron nitride layers caused fiber pull-out during fracture of long fiber reinforced composites, leading to a fracture toughness(Ki) value of3. 3 MPam 4. In contrast to this, the Zen Tron M glass fiber reinforced glass matrix composites with SnO2 interface exhibited brittle fracture o 2005 Elsevier B.V. All rights reserved Keywords: Glass matrix composites; Oxide fibres; Optomechanical composites; Interfaces; Fracture toughness 1. Introduction composites containing oxide fibers exhibiting suitable optical and thermomechanical properties, the so-calledoptomechani- The reinforcement of glass with ceramic fibers or particles is cal composites[7-13] a common approach to improve mechanical, thermo-mechanical The successful development of glass matrix composites and functional properties of this material [1-3]. Usually carbon with effective reinforcement and improved mechanical prop- or SiC fibers are used as reinforcing elements [1]. The resulting erties strongly depends on achieving optimal properties of glass matrix composites are useful lightweight materials, e.g. fiber-matrix interfaces. The responsible mechanisms for rein- for the manufacturing of specialized machine parts, such as hot forcement and enhancement of fracture toughness in these brittle glass and metals handling tools [4], or for other applications in matrix composites, such as crack bridging, crack deflection, fiber the aerospace machinery and automotive sectors [1-3, 5, 6] debonding or fiber pull-out are well understood [1, 2]. In the nfortunately, in the course of the manufacturing process the case of oxide fiber reinforced glass matrix composites, special outstanding glass property itself-optical transparency -is lost attention should be placed ( besides the optical compatibility of because of the black carbon or SiC fibers used or due to the fibers and glass matrix)on engineering the microstructure of different optical properties of the composite constituents. The the interfaces, due to the possibility of extensive chemical reac- formation of carbon-rich interphases due to reactions between tions between the fibers and the silicate matrix during processing fibers and matrix is another reason leading to opaque com- [14-16]. Many different interfaces have been studied to deter- posites [3-5]. Therefore, current research efforts are focused mine their suitability in glass matrix composites reinforced by on the development of transparent or translucent glass matrix oxide fibers [ 12-16]. The main role of the interfaces is to prevent a strong bonding of fiber and matrix during the technological steps of composite manufacturing, and thus to enable a sliding ng author.Tel:+44207594673l;fax:+442075946757 process between fiber and matrix during fracture From the opti- E-mail address: a boccaccini@ imperial ac uk(A R. Boccaccini) cal point of view, besides meeting the mechanical and thermal 0921-5093/S-see front matter Elsevier B V. All rights reserved doi:10.1016 J.msea.2005.11001Materials Science and Engineering A 417 (2006) 341–347 Mechanical properties of oxide-fiber reinforced glass matrix composites with BN or SnO2 interfaces D. Raab a, K. Pfeifer a, D. Hulsenberg ¨ a, A.R. Boccaccini b,∗ a Technische Universit ¨at Ilmenau, Institut f ¨ur Werkstofftechnik, Gustav-Kirchhoff-Str. 6, D-98693 Ilmenau, Germany b Imperial College London, Department of Materials, Prince Consort Road, London SW7 2BP, UK Received in revised form 28 October 2005; accepted 3 November 2005 Abstract With the aim of developing optomechanical inorganic materials, boron nitride-coated NextelTM 440 fibers and tin oxide-coated ZenTronTM glass fibers were used for manufacturing continuous and short fiber reinforced borosilicate glass matrix composites. No evident loss in tensile strength occurred for the BN-coated NextelTM fibers whereas coating the ZenTronTM fiber with tin oxide caused a significant strength decrease. Composites with ≤12 vol% of short or continuous fibers were fabricated by a standard slurry infiltration and hot-pressing process. The mechanical properties of the composites were investigated by uni- and biaxial flexural strength tests. NextelTM 440 short fiber reinforced composites with boron nitride interfaces demonstrated “quasi”-ductile fracture behaviour under biaxial stress loading with biaxial fracture strength values of up to 88 MPa. The boron nitride layers caused fiber pull-out during fracture of long fiber reinforced composites, leading to a fracture toughness (Kic) value of 3.3 MPa m1/2. In contrast to this, the ZenTronTM glass fiber reinforced glass matrix composites with SnO2 interface exhibited brittle fracture behaviour. © 2005 Elsevier B.V. All rights reserved. Keywords: Glass matrix composites; Oxide fibres; Optomechanical composites; Interfaces; Fracture toughness 1. Introduction The reinforcement of glass with ceramic fibers or particles is a common approach to improve mechanical, thermo-mechanical and functional properties of this material [1–3]. Usually carbon or SiC fibers are used as reinforcing elements [1]. The resulting glass matrix composites are useful lightweight materials, e.g. for the manufacturing of specialized machine parts, such as hot glass and metals handling tools [4], or for other applications in the aerospace machinery and automotive sectors [1–3,5,6]. Unfortunately, in the course of the manufacturing process the outstanding glass property itself – optical transparency – is lost because of the black carbon or SiC fibers used or due to the different optical properties of the composite constituents. The formation of carbon-rich interphases due to reactions between fibers and matrix is another reason leading to opaque com￾posites [3–5]. Therefore, current research efforts are focused on the development of transparent or translucent glass matrix ∗ Corresponding author. Tel.: +44 207 5946731; fax: +44 207 5946757. E-mail address: a.boccaccini@imperial.ac.uk (A.R. Boccaccini). composites containing oxide fibers exhibiting suitable optical and thermomechanical properties, the so-called ‘optomechani￾cal composites’ [7–13]. The successful development of glass matrix composites with effective reinforcement and improved mechanical prop￾erties strongly depends on achieving optimal properties of fiber–matrix interfaces. The responsible mechanisms for rein￾forcement and enhancement of fracture toughness in these brittle matrix composites, such as crack bridging, crack deflection, fiber debonding or fiber pull-out are well understood [1,2]. In the case of oxide fiber reinforced glass matrix composites, special attention should be placed (besides the optical compatibility of fibers and glass matrix) on engineering the microstructure of the interfaces, due to the possibility of extensive chemical reac￾tions between the fibers and the silicate matrix during processing [14–16]. Many different interfaces have been studied to deter￾mine their suitability in glass matrix composites reinforced by oxide fibers[12–16]. The main role of the interfaces is to prevent a strong bonding of fiber and matrix during the technological steps of composite manufacturing, and thus to enable a sliding process between fiber and matrix during fracture. From the opti￾cal point of view, besides meeting the mechanical and thermal 0921-5093/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2005.11.001