Spatiotemporal dynamics of coarse woody debris in a topographically complex, old-growth, deciduous forest

Jessica Glynda-Lee Davis


The focus of this study was to investigate the effect of graphene content on physical, mechanical, and tribological behavior of epoxy resin. Four composite samples, consisting of 0, 1%, 5%, and 10wt% graphene were fabricated using a 3 roll mill for dispersion and heat press for curing. Friction and wear tests were conducted on a laboratory scale tribo-test dynamometer, using a ring-on-flat configuration, for one hour duration at an average sliding speed of 0.3 m/s under a variable pressure of 0.26 to 0.39 MPa. Dynamic mechanical analysis (DMA) was used to determine the storage and loss moduli and contact angle measurements were determined to compute the surface energy of worn and unworn composite samples. Scanning electron microscopy and polarized light microscopy was used to study the graphene dispersion in the epoxy and study the wear mechanisms. In addition, electrical conductivity was measured to determine the percolation threshold and as an alternate method to verify the graphene dispersion in the epoxy. The tests indicate that storage modulus and surface energy increased by 62.5% and 55% respectively with graphene content. The tribological behavior of graphene composites showed that this nanofiller was very effective in stabilizing the coefficient of friction and reducing wear rate as well. Neat epoxy showed a high wear rate and an unstable coefficient of friction. On the other hand, 5wt% of graphene exhibited the highest stable coefficient of friction. The improvement on wear resistance was remarkable, for example, the 10wt% composite resulted in a wear reduction of almost 98% when compared with the neat epoxy. It may be noted that the manufacture of graphene based composites was relatively easy, quick, and inexpensive while the samples exhibited improvements in many relevant properties.