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. The composite uses a porous matrix instead of riser coatings to deflect cracks from the fibers. A processing method involving recently developed methods for reshaping and forming saturated high-volume fraction (>50 vol%) particle bodies was used to form the composite. Good infiltration of the woven fiber 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 against densification during use and thereby prevents forming cracklike voids and retains sufficient porosity for crack deflection. Measurements of interlaminar shear strength and strength of the composite show that composite produced by this processing method is comparable to previous all-oxide materials produced using the oxide fibers used here. The mechanical properties are rationalized in terms of the features on the fracture surfaces. Disintegration of the matrix to allow energy dissipation during fracture was apparent and correlates with the measurements of the fracture toughness of the material. Moderate notch insensitivity was demonstrated with a net section strength in the presence of a notch being 700% of the unnotched strength.