Processing and properties of an all-oxide composite with a porous matrix

Processing and mechanical properties of an all-oxide fiber composite with a porous matrix are presented here. The processing approach for an all-oxide composite was developed to be simple and involve one sintering process. Th e composite uses a porous matrix instead of riser coatings to deflect crack s from the fibers. A processing method involving recently developed methods for reshaping and forming saturated high-volume fraction (> 50 vol%) parti cle bodies was used to form the composite. Good infiltration of the woven f iber tows was obtained. Sintering in a pure HCl gas atmosphere was used to produce a porous matrix without shrinkage during processing. The sintering process also produced coarsening which makes the microstructure stable agai nst densification during use and thereby prevents forming cracklike voids a nd retains sufficient porosity for crack deflection. Measurements of interl aminar shear strength and strength of the composite show that composite pro duced by this processing method is comparable to previous all-oxide materia ls produced using the oxide fibers used here. The mechanical properties are rationalized in terms of the features on the Fracture surfaces. Disintegra tion of the matrix to allow energy dissipation during fracture was apparent and correlates with the measurements of the fracture toughness of the mate rial. Moderate notch insensitivity was demonstrated with a net section stre ngth in the presence of a notch being 700% of the unnotched strength. (C) 2 000 Elsevier Science Ltd. All rights reserved.