MATERAL CHARACIERAAION ELSEVIER Materials Characterization 54(2005)75-83 Effect of thermomechanical loads on microstructural damage and on the resulting thermomechanical behaviour of silicon carbide fibre-reinforced glass matrix composites A.R. Boccaccinia,*. A.M. Torre. C.R. oldanib D.N. Boccaccinic Department of Materials, Imperial College London, Prince Consort Rd, London SW7 2BP UK DEpartamento de Materiales, Universidad Nacional de Cordoba, argentina Dipartimento di Ingegneria dei Materiali e dell'Ambiente, Universita di Modena e, Reggio Emilia, Modena, itah Received 23 July 2004; received in revised form 26 October 2004: accepted 5 November 2004 Abstract The development of microstructural damage in SiC fibre(Nicalon )reinforced glass matrix composites subjected to different mechanical and thermal loads was investigated by assessing the change of the thermal expansion coefficient and the resistance to impact loads of the composites. The thermal expansion coefficient, measured by dilatometry after thermal shock tests from 650C to room temperature, was found to be 'insensitive to microstructural damage such as matrix microcracking, matrix softening or matrix/fibre interface degradation. The impact resistance of the composites, measured by a pendulum-type apparatus, was high even after subjecting the samples to different thermomechanical loads, h as repetitive thermal shocks from 650C for up to 20 cycles. However, the samples showed an appreciable degradation of their impact resistance after thermal aging in air at 700C for 100 h. This was shown to be due to extensive porosity formation due to softening of the glass matrix and due to oxidation of the carbon-rich fibre/matrix interfaces C 2004 Elsevier Inc. All rights reserved Keywords: Glass matrix composites; Thermal expansion; Microstructural damage; Impact behaviour; Thermal shock; Thermal aging 1. Introduction Silicate glasses possess a combination of attractive properties as: high hardness, high resistance to Corresponding author. Tel. +44 20 7594 6731; fax: +44 20 che low density, high wear resistance, 75843194. insulating electrical properties and optical transpar E-mail address. aboccaccini@imperial ac uk ency. The main disadvantages that glasses present for (A.R. Boccaccini) technical applications are their extreme fragility, their 1044-5803/S- see front matter e 2004 Elsevier Inc. All rights reserved doi:10.1016 j. matcha.2004.11.0Effect of thermomechanical loads on microstructural damage and on the resulting thermomechanical behaviour of silicon carbide fibre-reinforced glass matrix composites A.R. Boccaccinia,*, A.M. Torreb , C.R. Oldanib , D.N. Boccaccinic a Department of Materials, Imperial College London, Prince Consort Rd., London SW7 2BP, UK b Departamento de Materiales, Universidad Nacional de Co´rdoba, Argentina c Dipartimento di Ingegneria dei Materiali e dell’Ambiente, Universita` di Modena e, Reggio Emilia, Modena, Italy Received 23 July 2004; received in revised form 26 October 2004; accepted 5 November 2004 Abstract The development of microstructural damage in SiC fibre (NicalonR) reinforced glass matrix composites subjected to different mechanical and thermal loads was investigated by assessing the change of the thermal expansion coefficient and the resistance to impact loads of the composites. The thermal expansion coefficient, measured by dilatometry after thermal shock tests from 650 8C to room temperature, was found to be dinsensitiveT to microstructural damage such as matrix microcracking, matrix softening or matrix/fibre interface degradation. The impact resistance of the composites, measured by a pendulum-type apparatus, was high even after subjecting the samples to different thermomechanical loads, such as repetitive thermal shocks from 650 8C for up to 20 cycles. However, the samples showed an appreciable degradation of their impact resistance after thermal aging in air at 700 8C for 100 h. This was shown to be due to extensive porosity formation due to softening of the glass matrix and due to oxidation of the carbon-rich fibre/matrix interfaces. D 2004 Elsevier Inc. All rights reserved. Keywords: Glass matrix composites; Thermal expansion; Microstructural damage; Impact behaviour; Thermal shock; Thermal aging 1. Introduction Silicate glasses possess a combination of attractive properties such as: high hardness, high resistance to chemical attack, low density, high wear resistance, insulating electrical properties and optical transpar￾ency. The main disadvantages that glasses present for technical applications are their extreme fragility, their 1044-5803/$ - see front matter D 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.matchar.2004.11.001 * Corresponding author. Tel.: +44 20 7594 6731; fax: +44 20 7584 3194. E-mail address:a.boccaccini@imperial.ac.uk (A.R. Boccaccini). Materials Characterization 54 (2005) 75 – 83