Martine Dubé

Three-Dimensional Printing of Multifunctional Nanocomposites: Manufacturing Techniques and Applications.

The integration of nanotechnology into three-dimensional printing (3DP) offers huge potential and opportunities for the manufacturing of 3D engineered materials exhibiting optimized properties and multifunctionality. The literature relating to different 3DP techniques used to fabricate 3D structures at the macro- and microscale made of nanocomposite materials is reviewed here. The current state-of-the-art fabrication methods, their main characteristics (e.g., resolutions, advantages, limitations), the process parameters, and materials requirements are discussed. A comprehensive review is carried out on the use of metal- and carbon-based nanomaterials incorporated into polymers or hydrogels for the manufacturing of 3D structures, mostly at the microscale, using different 3D-printing techniques. Several methods, including but not limited to micro-stereolithography, extrusion-based direct-write technologies, inkjet-printing techniques, and popular powder-bed technology, are discussed. Various examples of 3D nanocomposite macro- and microstructures manufactured using different 3D-printing technologies for a wide range of domains such as microelectromechanical systems (MEMS), lab-on-a-chip, microfluidics, engineered materials and composites, microelectronics, tissue engineering, and biosystems are reviewed. Parallel advances on materials and techniques are still required in order to employ the full potential of 3D printing of multifunctional nanocomposites.

Metal mesh heating element size effect in resistance welding of thermoplastic composites

The objective of this work is to determine the effects of metal mesh heating element size on resistance welding of thermoplastic composites. The materials to be resistance-welded consisted of carbon fiber/poly-ether-ketone-ketone (CF/PEKK), carbon fiber/poly-ether-imide (CF/PEI) and glass fiber/PEI (GF/PEI). Four different metal mesh sizes were used as heating elements. The samples were welded in a lap shear joint configuration and mechanically tested. Maximum Lap Shear Strengths of 52, 47 and 33 MPa were obtained for the CF/PEKK, CF/PEI and GF/PEI specimens, respectively. The ratio of the heating element’s fraction of open area and wire diameter was shown to be the most important parameter to be considered when selecting an appropriate heating element size.

Tension-tension fatigue behaviour of woven flax/epoxy composites

Understanding the fatigue performance of biocomposites is critical in order to increase their acceptance, but current literature in this area is mostly limited to nonwoven reinforcements. This paper considers the tension–tension fatigue of three different woven flax/epoxy composites, for which two of them are prepreg-based and the other is manufactured using the Vacuum Assisted Resin Transfer Moulding (VARTM) process. Good fatigue performance of flax fibres comparable to those exhibited by glass fibres has shown the potential of this material to be implemented in load-bearing applications. The results suggest that minimizing the crimp in the yarns is a major concern to increase the resistance to fatigue damage in this class of materials. In addition to the three mentioned composites, two hybrids of flax/glass/epoxy were manufactured using the same VARTM process to check if the fatigue stability of flax fibre is extendable to its hybrids. The results show that an increase in the strength is possible, while maintaining similar fatigue behaviour as the plain flax/epoxy composites.

Modeling and experimental investigation of induction welding of thermoplastic composites and comparison with other welding processes

A three-dimensional finite element model of the induction welding of carbon fiber/polyphenylene sulfide thermoplastic composites is developed. The model takes into account a stainless steel mesh heating element located at the interface of the two composite adherends to be welded. This heating element serves to localize the heating where it is needed most, i.e. at the weld interface. The magnetic, electrical, and thermal properties of the carbon fiber/polyphenylene sulfide composite and other materials are identified experimentally or estimated and implemented in the model. The model predicts the temperature–time curves during the heating of the composite and is used to define processing parameters leading to high-quality welded joints. The effect of the heating element size and input current on the thermal behavior is investigated, both experimentally and using the developed model. The welds quality is assessed through microscopic observations of the weld interfaces, mechanical testing, and observations of the fracture surfaces. A comparison with two other welding processes, namely resistance welding and ultrasonic welding is finally conducted.

Optimization of thermoplastic composites resistance welding parameters based on transient heat transfer finite element modeling

The use of resistance welding technology to join thermoplastic composite aerospace structures is still contingent upon a better understanding of the heat transfer mechanisms occurring during welding, which govern the joint quality and mechanical performance. In this study, two-dimensional (2D) and three-dimensional (3D) transient heat transfer finite element models were developed to simulate resistance welding of thermoplastic composites. The 2D model was used to investigate the effect of the length of the exposed areas of the heating element to air (clamping distance) on the local overheating at the edges and the effects of the input power level on the thermal behavior of the welds. It is shown that controlling the clamping distance improves the thermal uniformity of the weld. The 3D model shows that heat conduction along the length of the laminates influences the thermal uniformity of the weld interface. An optimization chart is developed in order to minimize the undesirable edge effect and to define the conditions required to obtain a complete weld. The results of the 3D model are compared with experimental data.

Characterization of resistance-welded thermoplastic composite double-lap joints under static and fatigue loading

An experimental investigation of resistance welding of thermoplastic composite double lap shear (DLS) joints is presented. DLS specimens consisting of unidirectional carbon fibre/polyetheretherketone (CF/PEEK), carbon fibre/polyetherketoneketone (CF/PEKK), carbon fibre/polyetherimide (CF/PEI) and 8-harness satin weave fabric glass fibre/polyetherimide (GF/PEI) composites were resistance welded using a stainless steel mesh heating element. The welded specimens were tested under static and fatigue loadings, and the quality of the welds was examined using optical and scanning electron microscopy. Weld strengths of 53, 49, 45 and 34 MPa were obtained for CF/PEEK, CF/PEKK, CF/PEI and GF/PEI DLS joints, respectively. Indefinite fatigue lives were obtained between 20 and 30% of the ultimate static failure loads of the joints. Performances of the resistance-welded DLS and single lap shear (SLS) joints were compared. It was shown that the effect of joint geometry, that is, DLS versus SLS, on the mechanical performance of the resistance-welded joints is minimal, indicating a good resistance of welded joints to peel stresses.

Development of a morphing wing extrados made of composite materials and actuated by shape memory alloys

This article focuses on the development of a shape morphing composite skin representing a wing extrados. The objective is to design and manufacture a skin capable of changing its geometry in order to improve its aerodynamic efficiency. One geometry is considered to be the nominal geometry and a deformed geometry is identified. It is obtained upon application of a displacement at the aftmost boundary of the active portion of the wing profile. The displacement is imposed on the skin by shape memory alloy wires. These actuators are combined with a self-locking transmission mechanism that maintains the deformed geometry without any further energy consumption. The lay-up of the composite skin is optimised such that the deformed profile approaches the desired geometry as closely as possible. This lay-up selection routine is done through an ANSYS Parametric Design Language sub-routine. The finite element model is validated experimentally by conducting mechanical testing on the composite skin.

Preparation of hydrophobic nonwoven using recycled jute fibre and a titanium dioxide/fatty acid coating

E Arc Furnace (EAF) usage in producing steel is gaining importance day by day due to its special advantages. During smelting and refining of steel, the gases leaving the furnace carries a substantial amount of fine dust particles. The amount of dust generated is usually in the range of 9-18 kg per ton of scrap melted. The dust is important resource for the recovery of zinc and always better than its disposal as landfill. In order to recover zinc, the hydrometallurgical processes have been considered which are more eco-friendly and produces residues suitable for safe disposal as zinc could be selectively dissolved in suitable lixivants viz. sulphuric acid, hydrochloric acid, ammoniacal solution, sodium hydroxide have been used on bench scale. Sodium hydroxide however is selective for zinc dissolution but it needs further development for the metal recovery from the sodium zincate solution by electrolysis. Processes based on hydrochloric acid have not yet found any commercial application due to non-selective leaching and costly material of construction. Sulphuric acid have been found to be effective reagents for treatment of EAFD. The present paper examines and optimizes various parameters to recover zinc from EAF dust.

6.13 Additive Manufacturing of Multifunctional Nanocomposites and Composites

There is currently an increasing effort toward manufacturing of three-dimensional (3D) high-end products using additive manufacturing (AM) approach. The main limitations of the common AM techniques have been the limited choice of compatible materials combined with the nonfunctionality (e.g., electrical and thermal insulating) and relatively low mechanical strength of conventional printing materials (e.g., pure polymers). The main goal of this chapter is to review the different state-of-the-art AM methods compatible with nanocomposite and composite materials; explain the material designs, manufacturing parameters and the printed system properties, functionalities, and applications. The printable composite materials are designed with multiple constituents in order to offer a wide variety of functionalities (e.g., electrical and thermal conductivities, magnetism, piezoresistivity) to 3D structures at the nano, micro, or macroscales.

Preparation of a hydrophobic recycled jute-based nonwoven using a titanium dioxide/stearic acid coating

Abstract This work aims at developing a hydrophobic treatment for jute fiber-based nonwovens. Three solutions of titanium dioxide (TiO2) nanoparticles were prepared through a sol–gel method by varying the molar ratio of the various constituents. The nonwoven was pretreated with these solutions before being impregnated with different concentrations of stearic acid. The TiO2 nanoparticles synthesized are amorphous; their size varies with the concentration of ethanol used as a solvent in the sol–gel method. The nanoparticle coating produced on the jute fibers is uniform. The nonwoven wettability was evaluated by measuring its water contact angle and retention time; the nonwoven became hydrophobic at the lowest fatty acid concentration tested. An increase in the stability of the hydrophobicity was observed when the TiO2 nanoparticle pretreatment was used compared to the application of the stearic acid treatment only. No detrimental effect of the hydrophobic treatment on the nonwoven mechanical performance and thermal stability was observed. These results demonstrate the potential of the TiO2 nanoparticle/stearic acid treatment as a fast method to provide a stable hydrophobicity to recycled jute-based nonwovens.