Viscoelastic and Mechanical Properties of Multi-layered Graphene Polyester Composites

In this study, multi-layered-graphene (MLG) reinforced unsaturated polyester (UP) were prepared by adding different weight percentage of graphene in polyester resin and subsequently cross linked using mixture of methyl ethyl ketone peroxide. The mechanical properties of polyester-graphene were also studied. The maximum increase Tg was obtained from 80.85°C to 87.59°C in case of 0.7 wt%. The Vickers microhardiness (HV) was increased up to 116% compared to monolithic polyester. Flexural modulus of 0.7 wt% reinforcement recorded the highest modulus with 1.19Gpa. It was found that the addition of multi-layered graphene significantly improved the dynamic and mechanical properties of the composites

Effect of cutting tools and working conditions on the machinability of TI-6AL-4V using vegetable oil-based cutting fluids

The cutting of titanium alloys is usually associated with low productivity, poor surface quality, short tool life and high machining costs. This is due to the excessive generation of heat in the cutting zone and difficulties in heat dissipation due to the relatively low heat conductivity of this metal. Cooling applications in machining processes are crucial, since many operations cannot be performed efficiently without cooling. Improving machinability, increasing productivity, and enhancing surface integrity and part accuracy are the main advantages of the use of cutting fluids (CFs). Conventional cutting fluids such as mineral oil-based, synthetic and semi-synthetic fluids are the most common types used in the machining industry. Although these cutting fluids can be beneficial, they pose a great threat to human health and to ecosystems. Vegetable oils (VOs) are being investigated as a potential source of environmentally favourable lubricants, due to a combination of biodegradability, good lubrication properties, low toxicity, high flash points, low volatility, high viscosity indices and thermal stability. The fatty acids of vegetable oils are known to provide thick, strong, and durable lubricant films. These strong lubricating films give the vegetable oil base stock a greater capability to absorb pressure and a high load carrying capacity. This paper details the main experimental results from an investigation of the impact of various vegetable oil-based cutting fluids, cutting tool materials and working conditions when turning Ti-6Al-4V. A full factorial experimental design was employed involving 24 trials to evaluate the influence of process variables on average surface roughness (Ra), tool wear and chip formation. In general, values of Ra varied between 0.5 µm and 1.56 µm and the Vasco1000 cutting fluid exhibited a level of performance comparable to other fluids in terms of surface roughness, while the uncoated coarse grain WC carbide tool achieved lower flank wear at all cutting speeds. On the other hand, all tools tips were subject to uniform flank wear during the cutting trials. Additionally, formed chip thickness (tc) ranged between 0.1 mm and 0.14 mm with a noticeable decrease in chip size when higher cutting speeds were used

An Investigation into CO2 Laser Trimming of CFRP and GFRP Composites

The paper outlines results for an investigation of CO2 laser trimming of fibre reinforced plastic (FRP) composites. Process variables include cutting speed, laser beam power, gas pressure and workpiece material. These have been evaluated against key response measures involving material removal rate (MRR), surface roughness and kerf width. Higher MRRs have been obtained when trimming GFRP. Maximum MRR of 8 cm3/min was acquired when trimming GFRP at 1750 mm/min, 5 bar and 2500 watt respectively. Scanning electron microscope (SEM) analysis revealed that matrix constituent in both composites incurred to elevated cutting temperature which most likely resulted in a charring/melting and adhered to the cut surface which adversely affected its quality (Ra of up to ∼ 6 μm). Maximum entry kerf width of 0.5 mm and 0.28 mm was measured for GFRP and CFRP samples respectively

Weld overlay cladding repair - An investigation of tensile strength variation in processed metallic substrate

Weld Overlay Cladding (WOC) is a surfacing technique commonly applied on subsea Oil and Gas components to provide additional properties such as wear and corrosion resistance at a more superior level. This process involves a clad metal with certain desirable characteristics – tends to be a superalloy – being fusion-welded onto a lower cost standard metallic substrate such as steel. In some cases, a repair is required to recondition damaged or corroded clad surfaces. This paper presents an investigation on tensile strength variation that occurs in the metallic substrate post-repair. Tensile tests were carried out on specimens extracted from a repaired substrate and a section of unclad substrate. Results were compared and have shown that variations occurred in both pieces – neither were close to the values stated on the material certificate or previous test certificate. Through literature review, suggestions were made for the reasons behind this phenomenon. Recommendations were proposed as to how such non-uniformity can be prevented or rectified through amending material procurement and cladding procedure

Experimental investigation on micromachining of epoxy/graphene nano platelet nanocomposites

This paper investigates the effect of graphene nano platelet (GNP) content (%weight fraction) on the machinability of epoxy/GNP nanocomposites. The machinability of nanocomposites with varying loadings of GNP content was evaluated experimentally through the characterisation of cutting forces, surface morphology, chip morphology and tool wear. The minimum chip thickness phenomena of epoxy/GNP occurred at feed per tooth (FPT) between 0.2 and 0.4 μm. In order to achieve to better surface quality, the FPT should be over 0.4 μm. Epoxy/GNP with 1.0 wt% nanocomposite has produced the highest cutting force of a feed rate of ~ 3 N at 12 μm/rev. Epoxy/GNP nanocomposites exhibit the different cracking tendencies compared with plain epoxy, and the tool wear for GNP/epoxy nanocomposites is very small compared with metal nanocomposites. There is no significant difference in slot width accuracy between different types of tools, such as uncoated tool, diamond-like carbon-coated and diamond-coated tools

Modelling of cutting fibrous composite materials: current practice

Using fibre reinforced polymers (FRP) is increasing across many industries. Although FRP are laid-up in the near-net shape, several cutting operations are necessary to meet quality and dimensional requirements. Modelling of cutting is essential to understand the physics of the cutting phenomena and to predict quality and cost of products. This paper aims at reviewing the current practice in modelling of cutting FRP including analytical, numerical, mechanistic and empirical approaches, with emphasis on analytical models of cutting forces and delamination. Processes detailed include orthogonal cutting, drilling, milling and turning. Finally, advances in machining of metal-composite stacks are presented

Drilling of carbon fibre reinforced plastic composites

Following an extensive literature survey focusing on the machinability of carbon fibre reinforced plastics (CFRP), three main phases of experimental work were undertaken to evaluate the drilling of CFRP and associated stack materials. Phase 1 and 2 involved small diameter holes (1.5 mm) in thin CFRP laminates (3 mm thick) while Phase 3 addressed the feasibility of one-shot drilling (6.35 mm diameter holes) in multilayer workpiece stacks comprising titanium, CFRP and aluminium. Machinability was assessed in terms of tool life/wear, force/torque, hole size and geometrical accuracy, workpiece surface integrity and chip morphology

Meshfree formulation for modelling of orthogonal cutting of composites

The Element-Free Galerkin method (EFG) is a prominent member of the meshfree methods family. In this work, EFG is utilised to simulate the orthogonal cutting process of unidirectional composites. The mathematical model is derived from the weak form of the momentum conservation equation with frictional contact constraints based on penalty method. Spatial discretisation using moving least squares shape functions are used. The onset and progression of damage are predicted by two stress-based failure criteria. Full Newton Raphson solver is used to solve the non-linear system equations iteratively. Numerical experiments investigating the effect of rake angle and fibre orientation are conducted. Cutting forces are compared against experiments and finite element simulations available in literature. Simulations show that the meshfree model is capable of predicting cutting forces as a function of the fibre orientation. Sensitivity analysis is conducted to investigate the effect of important meshfree parameters such as the domain of influence and weight function on forces. One of the strongest advantages of the proposed model is the simple and automatic set up process, as meshing for domain discretisation is not required