A DOUBLE INCLUSION MODEL FOR MICROCRACK ARREST IN FIBER REINFORCED BRITTLE MATERIALS

A model for the prediction of microcrack growth in a fibre reinforced brittle matrix composite material is suggested. The model is based on composite material theory and linear elastic fracture mechanics. The microcracks in question are so-called large microcracks, i. e. , microcracks which are bridged by the reinforcing fibres. The crack bridging fibres are 'smeared' out to form a homogeneous medium. This homogeneous medium constitutes together with the matrix crack an ellipsoidal so-called 'double inclusion. ' Matrix cracking as well as interfacial debonding can be analysed and this analysis can be synthesized and interpreted as a determination of the strength of the reinforced matrix. The model is compared with some experimental results, and good agreement is found. The model can serve as a tool for the design of brittle matrix composite materials because it identifies the significance of fibre geometry, volume fraction of fibres, and adhesion between fibres and matrix.