Seawater aging response was investigated in marine-grade glass/epoxy, glass/vinyl ester, carbon/epoxy and carbon/vinyl ester composites with respect to water uptake, interlaminar shear strength, flexural strength, tensile strength, and tensile fracture surface observations. The reduction of mechanical properties was found to be higher in the initial stages which showed saturation in the longer durations of seawater immersion. The flexural strength and ultimate tensile strength (UTS) dropped by about 35% and 27% for glass/epoxy, 22% and 15% for glass/vinyl ester, 48% and 34% for carbon/epoxy 28%, and 21% carbon/vinyl ester composites respectively. The water uptake behavior of epoxy-based composites was inferior to that of the vinyl system.

Low-velocity instrumented impact tests were carried out on sandwich panels made of glass fiber-reinforced plastic facesheets and polyurethane foam core. The tests were carried out using a drop weight instrumented impact tester, connected to a data acquisition system. Four different types of sandwich samples using polyester/e-glass and epoxy/e-glass facesheet materials and polyurethane foam were considered for investigation. Two different face sheet materials were chosen to experimentally examine the effect of their elastic modulus on the impact response of the sandwich structures. The data acquisition system records the impact data such as impact force, penetration time and depth of penetration, and plots impact force versus depth of penetration and penetration time versus depth of penetration curves. From the recorded data the impact parameters such as maximum impact force, penetration time and depth of penetration versus impact energy were plotted to study the impact behavior. The results show that higher impact energy is required to break the epoxy/e-glass facesheet and backsheet sandwich specimens than other types of specimens examined. The impact damage caused to the facesheet, the core and the backsheet were thoroughly studied experimentally and the extent of damage caused to the facesheets and the core were also compared by finite element analyses.

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This paper presents results of the processing of nanocomposites based on epoxy and nanofillers, namely multiwalled carbon nanotubes (up to 10 wt%) and carbon black (up to 15 wt%). The twin screw extruded nanocomposites showed increases in electrical and thermal conductivities, tensile strength, microhardness and glass transition temperature. Electrical conductivity increased on the order of 10 11 at 10 wt% of nanotubes loading and at 15 wt% of carbon black. Greater increases in thermal and mechanical properties were observed in cases of nanotube-dispersed composites more so than others. SEM and AFM were used to examine the dispersion of the fillers.

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