Honggang Zhu

Tensile properties degradation of GFRP composites containing nanoclay in three different environments

Glass fiber-reinforced polymer (GFRP) composite with neat epoxy matrix and GFRP nanocomposite with epoxy–organoclay nanocomposite matrix were prepared. Their tensile properties degradation at elevated temperatures and in alkaline as well as freeze–thaw cycling environments was studied by performing the uniaxial tension test. Optical microscope in the transmission mode was employed to observe the failed specimens. Results show that the tensile properties of both materials degrade with increasing testing temperature or increasing immersion time in alkaline solution. Interestingly, the degradation rate is reduced, though insignificantly, when epoxy nanocomposite is used as the matrix material. This can be attributed to the improved thermo-mechanical property and barrier property of epoxy nanocomposite. When exposed to freeze–thaw cycles, the tensile properties of both materials degrade first and then level off. However, in this case, organoclay introduction has little effect on the degradation rate of GFRP tensile properties. The failure mechanisms of both materials in different environments were also discussed.

Degradation of glass fiber-reinforced plastic composites containing nanoclay in alkaline environment

The durability of glass fiber-reinforced plastic (GFRP) composites made from neat epoxy and organoclay nanocomposite in the alkaline environment is studied. Accelerated tests are performed by immersing the composite plates in the alkaline solution at 60°C. The tensile test and dynamic mechanical thermal analysis test are performed to evaluate the residual tensile properties and thermo-mechanical properties of aged GFRPs, while Fourier transform infrared spectrometry, micro-indenter, and scanning electron microscopy are employed to characterize the deterioration of the matrix, fiber, and fiber–matrix interface in GFRPs. The tensile properties and storage modulus of the GFRP composites are reduced with increasing aging time. Interestingly, the reduction is significantly mitigated when the organoclay nanocomposite is used as the matrix material. Degradation of matrix material, weakening of fiber–matrix interfacial bonding, and corrosion of glass fibers contribute to the property reduction in both composites. The excellent barrier characteristics of organoclay in the matrix are responsible for the superior performance of the GFRPs made from nanocomposite matrix, which in turn reduces the degree of corrosion of glass fibers.

Thermal performance and flame retardancy studies of vinyl ester and glass fiber reinforced plastic composites containing nanoclay

The thermomechanical properties, thermal stability and flame retardancy of the organoclay-vinyl ester nanocomposites and the glass fiber reinforced plastic composites made from the vinyl ester nanocomposites matrix were studied. The results show that nanoclay addition increases both the storage modulus and glass transition temperature of the vinyl ester and glass fiber reinforced plastic composites due to the reinforcing effects and the molecular relaxing constraining effects of clay platelets. Both the vinyl ester and glass fiber reinforced plastic composites show different thermal degradation behaviors in nitrogen and in air due to the oxidizing effect of oxygen. Nanoclay has little effect on the thermal stability of vinyl ester in nitrogen, while increases the 2nd peak decomposition temperature of vinyl ester in air, resulting from the shielding effect of silicate platelets. However, the thermal stability of the glass fiber reinforced plastic composites in both atmospheres is reduced by nanoclay with unknown reasons. The flame retardancy of vinyl ester and glass fiber reinforced plastic composites is significantly improved due to clay that promotes the formation of carbonaceous char platelets acting as mass and heat barrier. Glass fiber reinforcement alters the thermal dynamic, thermal degradation and combustion behaviors of the vinyl ester nanocomposites.

Wear Resistance of Organic Nanocomposites

The wear resistance of epoxy-based nanocomposites reinforced with octadecylamine-modified clay was studied. Two testing methods, including the ball-on-disc abrasion test and the nanoscratch test, were used to measure the macro- and micro-wear behaviors. The ball-on-disc abrasion test suggests that the short- and long-term wear behaviors of neat epoxy and 5wt% nanoclay composites were similar, although the wear resistance as measured by the volume of material removed was greater for the clay nanocomposite than for the neat epoxy. The incorporation of nanoclay into the epoxy showed little effect on the coefficient of friction.