The main aim of this research was to investigate the effect of machining parameters towards surface quality during edge trimming process on a specific CFRP material. There were two variation of machining parameters focused in this work namely spindle speed (N) and feed rate (Vf). The CFRP panel is measured 3.25 mm in thickness and the type of fabric was unidirectional (UD). It has 28 number of plies in total and were arranged multi-directional. Router or burr tool geometry made of uncoated tungsten carbide with a diameter of 6.35 mm was used to perform the edge trimming process. Surface roughness measurement was taken using Mitutoyo Surftest SJ-410. Furthermore, optical microscope Nikon MM-800 is utilized to further observe the trimmed surfaces. The result reveals that the smallest value of the surface roughness (1.31 µm) is obtained by Run 8 (R8) which the spindle speed, N applied was 2506 rpm and feed rate, Vf at 376 mm/min. Meanwhile, the highest surface roughness value (12.62 µm) exhibited by the R9 which had the highest setting of spindle speed, N 7518 rpm and the highest feed rate, Vf 1128 mm/min. The result is supported by the observation of trimmed surface through optical microscopy which clearly exhibits uncut fibers and matrix degradation condition. Details results elaborated and discussed further in this paper.
This study focused on the relationship between adhesion force and withdrawal speed, which is one of the primary time-dependent characteristics of the surface force. Highly precise measurement of the surface force was conducted using a surface force apparatus. Polydimethylsiloxane (PDMS) and glass (BK7) were used for the spherical probe and Si wafer was used for the plate sample. The results showed that the adhesion force, adhesion displacement, and withdrawal energy increased as the withdrawal speed was increased when the PDMS probe and Si sample were used in combination. These characteristics could not be seen in the adhesion forces between BK7 and Si. Moreover, we proposed an empirical theoretical model of the PDMS-Si contact assuming viscoelasticity. The spring constant and the damping coefficient of the contact were formulated as functions of the withdrawal speed and the displacement with reference to the experimental results. It was found that the spring constant decreases and the damping coefficient increases as the displacement increases or the withdrawal speed decreases.
Copper based particles were synthesized by a wood-powder-template-based process. Wood powders mixed with an aqueous cooper salt solution were heated under N2 gas flow, and then, the mixture of the charcoal powder and copper particles were heated in air to remove charcoal. Finally, oxidized wood-derived copper particles (OWCu) of less than 1 μm were synthesized. Wood powders acted as the template and limited the sizes of the copper particles. In addition, the tribological properties of OWCu in synthetic oil were investigated using a pin-on-plate reciprocating tribometer. Our results revealed that 0.5 mass% OWCu reduced both the friction coefficient (max 45%) and wear volume (max 39%) of SUJ2 lubricated by PAO4. The best reduction effect was obtained for OWCu synthesized at 400°C under N2 gas flow, which had the smallest average particle size, where the coverage of the OWCu layer on the wear track was the largest. These facts suggest that the particle size reduction of OWCu can increase the coverage and improve the friction coefficient and wear volume reduction effects of the lubricant. Control of the wood-powder-template-based synthesized particles to the optimal size for the roughness of the sliding surface would help achieve better tribological performance.
Graphene oxide (GO) and oxidized wood-derived nanocarbon (oWNC) were dispersed in an epoxy resin to improve the mechanical and tribological properties of an epoxy resin. Mechanical properties of the GO/epoxy (GO/EP) and oWNC/epoxy composites (oWNC/EP) were investigated by tensile tests and nano-indentation. Under dry, water, and oil lubrication conditions, friction coefficients and wear volumes of these composites were measured. GO has single-layered structure. oWNC has chain-like nanostructures, and the nanochains are aggregated. GO and oWNCs have same surface chemical composition due to the same oxidation treatment. Thus, in this study, the structure and morphology dependences of the nanocarbons in mechanical and tribological properties will be appeared when the nanocarbons were used as the additives in the resin. The tensile strength, tensile modulus, and hardness increased by 20%, 63%, and 35% in maximum by the addition of GO and oWNC to the epoxy resin, respectively. Moreover, the wear resistance of GO/EP and oWNC/EP was enhanced compared to that of a neat epoxy. The reduction rates of the wear volume for 5.0 mass% GO/EP and 1.0 mass% oWNC/EP achieved to 91% and 67%, respectively. Comparing GO and oWNC, oWNC effectively reduced the friction coefficient and wear at a lower concentration. The improvement of tribological properties after the addition of the oxidized nanocarbons can be attributed to the increase in the hardness and lubricity of the composites.
Climate change is affecting every being on the planet. The time has arrived to give a big push for harvesting renewable energy sources, thus reducing the dependencies on fossil fuels and chemical batteries. This inspired Nanotechnologists to explore energy harvesting techniques from the environment. Triboelectric nanogenerator (TENG) is one such emerging, promising, and a reliable technology to extract micropower from the abundantly available natural mechanical energy. In this study, we have addressed the durability issues of TENG using Diamond-like Carbon (DLC) films as a triboelectric surface. Our findings indicate a high potential for DLC films for TENG applications attributing to its outstanding tribological, mechanical and insulating properties. Hydrogenated DLC (H-DLC) film, Fluorinated DLC (F-DLC) film, and PTFE were used as dielectric surfaces on a rotary based sliding-TENG. The output performance of each pair differed with the sliding frequency where H-DLC/F-DLC pair produced the maximum output at a moderate frequency of 4 Hz. As the frequency was raised, H-DLC/PTFE pair exhibited the highest output at 10 Hz, equal to that of the Al/PTFE pair. The durability evaluation of DLC-TENG showed very promising outcomes producing stable output current for 2 h. This study is expected to encourage the development of DLC-based sliding-TENGs, with enhanced durability and output efficiency.
Regarding micropitting, which is one of the fatigue damages that occur under conditions where the oil film thickness is smaller than the surface roughness, the effects of hardness and roughness of the test piece and differences in lubricants were confirmed. Endurance tests and friction tests were conducted using two-disc test rig. On the condition with harder and rougher surface of test pieces, deeper micropits were produced. The phosphorus additive blended oil led to a shallower pit depth than the sulfur additive blended oil. It was further suggested that the friction coefficient had little effect on micropit progress, and the influence of the lambda ratio (ratio of the oil film thickness to the root mean square roughness) after initial running-in was large. In a surface of high hardness and high roughness, micropitting tend to progress more easily. However, it was found out that the progress can be suppressed by suitable lubricants additives.