In industries today, various applications require different materials properties. Some of these properties are hard to achieve from an individual material hence the need to combine one or more of the materials to form a composite. A material or a composite such as those formed from polymers can be reinforced by other materials to improve their mechanical properties hence making them less susceptible to mechanical failures.
Graphene sheets and carbon nanotubes, for example, have been widely used as the reinforcements in polymer composites. Several studies have proved that these materials have the desired properties such as light weights, specific surface area, thermal and mechanical which are crucial for the reinforcement purposes of polymer matrices. However, it has also become an area of interest in knowing which one between the graphene sheets and carbon nanotubes, is the best for polymer composite reinforcement especially for mechanical properties. This is in a bid of rightfully categorizing a particular application to a particular reinforcement type of a polymer composite material.
Professor Quan Wang from Southern University of Science and Technology in China with PhD student Yunlong Li and Professor Shijie Wang from Shenyang University of Technology in collaboration together with Professor Malcolm Xing from University of Manitoba in Canada, conducted a molecular dynamics simulation method to compare and contrast the effects of using carbon nanotubes and graphene sheets as reinforcement materials on the mechanical properties of polymer composites. They investigated Young’s modulus, surface crack energy and tensile strength properties of the polymer nano-composites. They also used models comprising of same masses for the two reinforcements. The research work is published in the journal, Composites part B: Engineering.
The authors choice of molecular dynamic simulations methods was because of its capability of giving a fundamental physical, behavioral analysis of materials at both microscopic and atomic levels in details. This was not the case with the methods used previously. In the simulations, the pull-out process was used as a compliment in the analysis of the intermolecular relationship of the reinforcement materials and the polymer matrices. The mechanical tensile properties of the polymer composites reinforced by carbon nanotubes and graphene sheets methods were studied using the strain constant method.
From the comparison of the three main mechanical properties investigated for the two polymer composite reinforcement materials that is, Young’s modulus, surface crack energy and tensile strength. The research team observed that graphene reinforced polymer composites exhibited better results as compared to carbon nanotubes reinforced polymers. For instance, Young’s modulus, tensile strength, and surface crack energy were found to be 18 percent, 8.7 percent and 5 percent respectively higher in graphene sheets than carbon nanotubes reinforcement.
According to the authors, graphene sheets overtakes carbon nanotubes because they are useful for delaying cracks propagation in the polymer materials by lowering the penetrating forces. Molecular dynamics simulation methods allow for atomic level analyzing which enables analysis of shear forces and van der Waals energy produced from the action between the polymer matrices and the applied nanoreinforcements. However, care should be taken while selecting reinforcement enhancing method to be used which should depend on the intended application for the polymer composite.
Li, Y., Wang, S., Wang, Q., & Xing, M. (2018). A comparison study on mechanical properties of polymer composites reinforced by carbon nanotubes and graphene sheet. Composites Part B: Engineering, 133, 35-41.
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