Fracture behaviour of hybrid glass matrix composites: Thermal ageing effects

The thermal aging of a glass matrix composite reinforced by short carbon fibres as well as by ZrO2 particles (hybrid composite) was investigated at temperatures in the range 500-700 °C for exposure durations of 24 h in air. The mechanical properties of as-received and aged samples were evaluated at room temperature by using the three-point flexure chevron notch technique. The fracture toughness values of as-received specimens were in the range 2.6-6.4 MPa m1/2. Fracture toughness was affected by the thermal aging conditions. For thermal aging at temperatures <700 °C, degradation of fibre-matrix interfaces occurred and therefore the apparent fracture toughness and flaw tolerant resistance decreased. For the most severe ageing conditions tested (700 °C/24 h), fracture toughness values dropped to 0.4 MPa m1/2. Significant degradation of the material was detected for this aging condition, mainly characterised by porosity formation in the matrix as a result of softening of the glass and oxidation of the carbon fibres. © 2003 Elsevier Ltd. All rights reserved.