Mechanical properties of oxide-fiber reinforced glass matrix composites with BN or SnO2 interfaces

With the aim of developing optomechanical inorganic materials, boron nitride-coated Nextel™ 440 fibers and tin oxide-coated ZenTron™ glass fibers were used for manufacturing continuous and short fiber reinforced borosilicate glass matrix composites. No evident loss in tensile strength occurred for the BN-coated Nextel™ fibers whereas coating the ZenTron™ fiber with tin oxide caused a significant strength decrease. Composites with <=12 vol% of short or continuous fibers were fabricated by a standard slurry infiltration and hot-pressing process. The mechanical properties of the composites were investigated by uni- and biaxial flexural strength tests. Nextel™ 440 short fiber reinforced composites with boron nitride interfaces demonstrated "quasi"-ductile fracture behaviour under biaxial stress loading with biaxial fracture strength values of up to 88 MPa. The boron nitride layers caused fiber pull-out during fracture of long fiber reinforced composites, leading to a fracture toughness (Kic) value of 3.3 MPa m^1/2. In contrast to this, the ZenTron™ glass fiber reinforced glass matrix composites with SnO2 interface exhibited brittle fracture behaviour.