FABRICATION AND MECHANICAL-PROPERTIES OF AN OPTICALLY TRANSPARENT GLASS-FIBER POLYMER MATRIX COMPOSITE

A composite with substantial optical transparency was produced by reinforcing poly(methyl methacrylate) (PMMA) with unidirectional borosilicate glass fibers. Optical transparency of the composite was achieved by matching the refractive index (n(D)) of the glass fiber and polymer matrix to within +/- 0.002. The optical transmission of the composite decreased with increasing volume percentage of glass fibers. Composites containing 30 volume percent of unidirectional 12-mu-m diameter fibers had a transmission at 589.3 nm of 20 percent measured through a 10 mm thickness. Composites containing 30 volume percent of 56-mu-m diameter fibers had an optical transmission of 45 percent. Type-written text could be clearly read through the composite when it was laid directly on a printed page. Composites with 40 volume percent fiber had a flexural strength of 600 MPa which is six times greater than that of pure PMMA. The flexural modulus for the same composite was 18 MPa which is nine times greater than the 2 MPa measured for pure PMMA. The work of fracture was 110 kJ/m2 or more than double the 45 kJ/m2 for pure PMMA. Suggestions are made for further improvements in the optical properties.