BS in Materials Engineering
Materials Engineering Department
Chopped strand mat E-glass layers were impregnated with isophthalic marine laminating resin by hand lay-up techniques. Once the primary laminate reached the desired Barcol hardness value, the secondary laminate was applied and allowed to cure. These samples were bonded together at hardness values of 10, 30, 50, 70, and 90 Barcol. Lamination was conducted at 70°F with 35% glass fibers and 65% polyester resin catalyzed with 1.5% methyl ethyl ketone peroxide. The target thickness of each laminate was 6mm for short-beam shear testing requiring eight layers of glass and resin. Using the procedures outlined in ASTM D-2344, each sample set of ten specimens was short-beam shear tested using a 20mm span with 0.125in diameter load nose and supports. The short-beam shear testing of each specimen forced interlaminar shear between the primary and secondary layers, allowing for characterization of the bond strength at different hardnesses. After preliminary testing, all samples showed statistically significant differences with a trend of increasing bond strength with decreasing hardnesses. Twenty percent of the samples delaminated while the other sample failed under flexure loads. The samples that were bonded at higher hardnesses failed under lower loads in tension and compression rather than in shear. Three-point bend testing following ASTM 7264 was conducted to determine the flexural stiffness and strength properties of the samples to determine the validity of preliminary testing. After secondary testing was completed, the preliminary data was confirmed and conclusions were drawn. It was found that hardness does not affect the strength of adhesion in composite laminates. These results suggest that the use of this particular resin-fiber system could eliminate the sanding manufacturing step used during lamination.