Forming of noncircular cross-section SiO2 glass fibers

Abstract

Silica glass fibers with triangular and rectangular cross-sections have been produced by two different means, namely preform drawing and powder extrusion. For the preform drawing method, silica glass rods were machined and polished to yield preforms with the desired cross-sections. These were then heated to temperatures in excess of 1600°C and drawn to fibers with approximately 265 μm × 265 μm × 265 μm triangular and 275 μm × 100 μm rectangular cross-sections exhibiting tensile strengths between 300 and 400 MPa and bending radii smaller than 50 mm. For the extrusion route, a silica nanopowder was compounded at ≈ 150°C with a polyethylene-based binder and extruded at similar temperatures through dies with the desired exit cross-section. The fibers were debound by thermally decomposing the binder and sintered at 1100°C to yield amorphous glass fibers with approximately 205 μm × 205 μm × 205 μm triangular and 275 μm × 90 μm rectangular cross-sections. Although the two manufacturing processes are radically different, both involve flow of a fluid with a temperature-dependent viscosity and this dictates that shape trueness (i.e. flat faces and sharp corners) is a function of the drawing and extrusion rates and the temperature during drawing and sintering.