MIATERIALS ENE S ENGINEERING ELSEVIER Materials Science and Engineering A278(2000)187-19 www.elsevier.com/locate/msea The mechanical behaviour of glass and glass-ceramic matrix composites K.-L. Choy a, * P. Duplock a, P.S. Rogers a, J. Churchman-Davies b, M.T. Pirzada Department of Materials, Imperial College of Science, Technology and Medicine, Prince Consort Road, London SW 2BP, UK b 5la Charlton Road, Wantage, Oxon, OX 12 8H. UK Received 10 November 1998: received in revised form 10 August 1999 Abstract The mechanical behaviour of several glass and glass-ceramic composites was studied, with particular interest in axial and off-axis properties. The embrittlement of a cross-ply composite of carbon fibre reinforced borosilicate glass was attributed to the formation of a fibre /matrix interfacial reaction layer during processing. The tensile properties for cross-ply BMAS(BaO, Mgo Al,O3, Sio,) glass-ceramic composites reinforced with silicon carbide fibres exhibited higher matrix cracking stresses in the 90 and 0 plies than the carbon fibre reinforced borosilicate glass composite. These were attributed to the presence of residual stresses that caused the glass-ceramic matrix in compression. Failure strengths in excess of 300 MPa were found for these glass-ceramic composites. Off-axis properties for cross-ply laminates were found to strongly depend on the volume fraction of fibres Composites with lower fibre volume fractions exhibited higher interlaminar strengths than those with higher fibre volume fractions. There also appeared to be a link between inhomogeneous microstructures and a larger variation in mechanical properties o 2000 Elsevier Science S.A. All rights reserved. Keywords: Glass; Glass-ceramics: Matrix composites; Mechanical properties 1. Introduction of faws must be combined with an increase in the resistance to crack growth and a decrease in the sensi- Advanced materials for structural applications at tivity of the strength to the size of those flaws that are high temperatures have been largely restricted to ad- present. These criteria have led to the development of vanced metallic alloys. In high temperature applica- ceramic composites, where two phases are combined tions, a sophisticated breed of Ni-, Co- and Fe-base with weak inter-linking bonds for crack deflection. Fi alloys has evolved both in terms of microstructural and bres of many different shapes, sizes and geometries can structural design. Nevertheless, the high temperature be embedded in a ceramic matrix. This paper is con- applications of such alloys are still restricted by the cerned with long fibre composites that contain rela melting points of the metals. For continued develop- tively large volume fractions of continuous aligned ment, ceramics offer one of the few avenues to a fibres in unidirectional composites or laminae, the lam significant increase in the service temperatures. Their inae being stacked together and consolidated to multi low density, low chemical reactivity and high hardness directional laminates. The technology is most advanced offer additional potential for extending performance for glass and glass-ceramic matrix systems, such as limits beyond those offered by metallic materials [1]. borosilicate lithium-alumina-silicate (Las),magne The reliability of structural ceramics in engineering sium-alumina-silicate(MAS)and barium osumilite applications is a major problem. Improving the proper- (BMAS). A slurry impregnation route is employed to ties of these brittle ceramic materials is achieved by flaw incorporate the fibres into the unconsolidated matrix, control and toughening [2]. A reduction in the incidence followed by hot pressing for consolidation. Most devel- opment work has been carried out using multifilament author. Tel /fax: +44-171-5946750 tary tows of small diameter(7-15 um) SiC or C fibres kchoy@ic ac uk(K.-L Choy) [3] 0921-5093/00/S- see front matter c 2000 Elsevier Science S.A. All rights reserved. PI:s0921-5093099)00572-9Materials Science and Engineering A278 (2000) 187–194 The mechanical behaviour of glass and glass–ceramic matrix composites K.-L. Choy a,*, P. Duplock a , P.S. Rogers a , J. Churchman-Davies b , M.T. Pirzada a a Department of Materials, Imperial College of Science, Technology and Medicine, Prince Consort Road, London SW7 2BP, UK b 51a Charlton Road, Wantage, Oxon, OX 12 8HJ, UK Received 10 November 1998; received in revised form 10 August 1999 Abstract The mechanical behaviour of several glass and glass–ceramic composites was studied, with particular interest in axial and off-axis properties. The embrittlement of a cross-ply composite of carbon fibre reinforced borosilicate glass was attributed to the formation of a fibre/matrix interfacial reaction layer during processing. The tensile properties for cross-ply BMAS (BaO, MgO, A12O3, SiO2) glass-ceramic composites reinforced with silicon carbide fibres exhibited higher matrix cracking stresses in the 90 and 0° plies than the carbon fibre reinforced borosilicate glass composite. These were attributed to the presence of residual stresses that caused the glass–ceramic matrix in compression. Failure strengths in excess of 300 MPa were found for these glass–ceramic composites. Off-axis properties for cross-ply laminates were found to strongly depend on the volume fraction of fibres. Composites with lower fibre volume fractions exhibited higher interlaminar strengths than those with higher fibre volume fractions. There also appeared to be a link between inhomogeneous microstructures and a larger variation in mechanical properties. © 2000 Elsevier Science S.A. All rights reserved. Keywords: Glass; Glass–ceramics; Matrix composites; Mechanical properties www.elsevier.com/locate/msea 1. Introduction Advanced materials for structural applications at high temperatures have been largely restricted to ad￾vanced metallic alloys. In high temperature applica￾tions, a sophisticated breed of Ni-, Co- and Fe-base alloys has evolved both in terms of microstructural and structural design. Nevertheless, the high temperature applications of such alloys are still restricted by the melting points of the metals. For continued develop￾ment, ceramics offer one of the few avenues to a significant increase in the service temperatures. Their low density, low chemical reactivity and high hardness offer additional potential for extending performance limits beyond those offered by metallic materials [1]. The reliability of structural ceramics in engineering applications is a major problem. Improving the proper￾ties of these brittle ceramic materials is achieved by flaw control and toughening [2]. A reduction in the incidence of flaws must be combined with an increase in the resistance to crack growth and a decrease in the sensi￾tivity of the strength to the size of those flaws that are present. These criteria have led to the development of ceramic composites, where two phases are combined with weak inter-linking bonds for crack deflection. Fi￾bres of many different shapes, sizes and geometries can be embedded in a ceramic matrix. This paper is con￾cerned with long fibre composites that contain rela￾tively large volume fractions of continuous aligned fibres in unidirectional composites or laminae, the lam￾inae being stacked together and consolidated to multi￾directional laminates. The technology is most advanced for glass and glass–ceramic matrix systems, such as borosilicate lithium–alumina–silicate (LAS), magne￾sium–alumina–silicate (MAS) and barium osumillite (BMAS). A slurry impregnation route is employed to incorporate the fibres into the unconsolidated matrix, followed by hot pressing for consolidation. Most devel￾opment work has been carried out using multifilamen￾tary tows of small diameter (7–15 mm) SiC or C fibres [3]. * Corresponding author. Tel./fax: +44-171-5946750. E-mail address: k.choy@ic.ac.uk (K.-L. Choy) 0921-5093/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved. PII: S0921-5093(99)00572-9