NACA Research Memorandums

Effects of humidity during fabric conditioning and during fabrication upon some physical properties of laminates prepared with glass fabric and an unsaturated polyester resin were investigated. Tests on these laminates included the measurement of flexural strength on the diagonal, both dry and after 7 days' immersion in water, specific gravity, resin content, percentage of voids, and total light transmission. Some data were also taken on lengthwise flexural strength. Effects of humidity during fabrication on flexural strength, both wet and dry, specific gravity, percentage of voids, and light transmission were pronounced when molding temperatures of 220 and 250 F were used. At a molding temperature of 160 F these effects were negligible