Abdulhakim A. Almajid

Manufacturing Aspects of Advanced Polymer Composites for Automotive Applications

Composite materials, in most cases fiber reinforced polymers, are nowadays used in many applications in which light weight and high specific modulus and strength are critical issues. The constituents of these materials and their special advantages relative to traditional materials are described in this paper. Further details are outlined regarding the present markets of polymer composites in Europe, and their special application in the automotive industry. In particular, the manufacturing of parts from thermoplastic as well as thermosetting, short and continuous fiber reinforced composites is emphasized.

Design of bimorph piezo-composite actuators with functionally graded microstructure

Piezoelectric actuators with functionally graded microstructure (FGM) are designed with the aim of reducing the stress concentration at the middle interface that exists in the standard bimorph actuators while maintaining high bending displacement. A FGM piezoelectric laminate consists of a number laminae, which are composite materials with electroelastic properties varied through the laminate thickness. The electroelastic behavior of piezo-actuators with laminated composite is studied by two-stage hierarchical model, the first based on the Eshelby’s model for predictions of the electroelastic properties of each lamina, the second based on classical lamination theory (CLT). The in-plane stresses and out-of-plane displacements are obtained by the CLT for both standard and FGM piezoelectric bimorph actuators under the assumption of cylindrical bending. The microstructure of the FGM biomorph actuator is optimized by using CLT model to achieve the best performance of the FGM piezoelectric actuator, i.e. large bending displacement while minimizing the induced stress field. Based on the optimized microstructure of the FGM bimorph actuators by the CLT model, we processed the FGM bimorph actuator that is composed of six laminae, and also the standard bimorph actuator. The bending displacements of these actuators are then measured by a laser displacement measurement apparatus as a function of applied voltage. The measured data of the bending displacements versus applied voltage are compared with the predictions by the CLT, resulting in a good agreement.

Amorphous SiO2 NP-Incorporated Poly(vinylidene fluoride) Electrospun Nanofiber Membrane for High Flux Forward Osmosis Desalination

Novel amorphous silica nanoparticle-incorporated poly(vinylidine fluoride) electrospun nanofiber mats are introduced as effective membranes for forward osmosis desalination technology. The influence of the inorganic nanoparticle content on water flux and salt rejection was investigated by preparing electrospun membranes with 0, 0.5, 1, 2, and 5 wt % SiO2 nanoparticles. A laboratory-scale forward osmosis cell was utilized to validate the performance of the introduced membranes using fresh water as a feed and different brines as draw solution (0.5, 1, 1.5, and 2 M NaCl). The results indicated that the membrane embedding 0.5 wt % displays constant salt rejection of 99.7% and water flux of 83 L m(-2) h(-1) with 2 M NaCl draw solution. Moreover, this formulation displayed the lowest structural parameter (S = 29.7 μm), which represents approximately 69% reduction compared to the pristine membrane. Moreover, this study emphasizes the capability of the electrospinning process in synthesizing effective membranes as the observed water flux and average salt rejection of the pristine poly(vinylidine fluoride) membrane was 32 L m(-2) h(-1) (at 2 M NaCl draw solution) and 99%, respectively. On the other hand, increasing the inorganic nanoparticles to 5 wt % showed negative influence on the salt rejection as the observed salt flux was 1651 mol m(-2) h(-1). Besides the aforementioned distinct performance, studies of the mechanical properties, porosity, and wettability concluded that the introduced membranes are effective for forward osmosis desalination technology.

Effect of Equal-Channel Angular Pressing Process on Properties of 1050 Al Alloy

Annealed 1050 Al samples with coarse-grained microstructure of 600 µm were equal-channel angular pressing (ECAP) processed using two routes, A and BC. The samples were processed up to four passes through a die with an internal angle of 90o using both routes. Electron back-scattered diffraction (EBSD) technique was used to study the developed microstructure after ECAP processing. The cell size distribution, misorientation, and the fraction of high angle boundaries were determined. The microstructure study was conducted on both the extrusion direction and the shear plane. The produced microstructure depends on the used route and number of passes. A study of mechanical behavior was conducted by using tensile and compression specimens from the specimens produced by ECAP in the extrusion direction. Enhanced strength was observed but with anisotropic behavior between tension and compression. The dimple size and distribution on fractured surface of tensile specimens was affected by the ECAP route and number of passes.

Poly-Para-Phenylene-Copolymer (PPP): A High-Strength Polymer with Interesting Mechanical and Tribological Properties

This paper illustrates the high strength and modulus of a poly-para-phenylene-copolymer in comparison to other high-performance polymers. In particular, it outlines how its microhardness, fracture toughness, scratch resistance and specific wear rate against steel compare to corresponding values of polyether ether ketone.

A TiO2 nanofiber/activated carbon composite as a novel effective electrode material for capacitive deionization of brackish water

Based on its excellent characteristics, high surface area, environmentally safe and availability in nature; activated carbon (AC) is the best candidate as a capacitive deionization (CDI) electrode material. Among the various modification methods for AC, incorporation of TiO2 nanoparticles into the activated carbon proved to be an effective approach to enhance the desalination performance. Compared to the nanoparticulate morphology, nanofibers have a large axial ratio which provides a better electrosorption performance. Herein, for the first time, TiO2 nanofibers (TNFs) prepared by the electrospinning process were exploited with activated carbon to form a hybrid network electrode for capacitive deionization. The phase morphology and crystal structure were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The electrochemical behavior was evaluated by cyclic voltammetry (CV). Furthermore, the desalination performances under different applied voltages and salty water concentrations were investigated using a prototype CDI unit in a continuous mode water flow. The results indicated that the electrode prepared from 10 wt% nanofibers (ACTNF 10%) exhibits the best results compared to other electrodes having 5 and 15 wt% TiO2 nanofibers. Typically, the best electrode networks showed very good specific capacitance (380 F g−1), excellent electrosorptive capacity (17.7 mg per gcarbon) at a cell potential of 1.2 V and an initial NaCl concentration of 292 mg L−1, and a distinguished salt removal efficiency (∼89.6%). Moreover, the introduced electrode shows interesting recyclability and easy full regeneration.

Effect of Solution Heat Treatment on the Hot Workability of Al–Mg–Si Alloy

The current work presents a detailed study on the high temperature processing of solution treated Al–Mg–Si alloy in the temperature range of 623 K to 773 K and at different strain rates in the range of 5 × 10−5 to 6 × 10−2 s−1. A constitutive relation that can be used in modeling the forming process of this alloy under similar hot working conditions is established. Also, the prevailing deformation mechanism was investigated through relations of the steady state stress dependence on strain rate which revealed a stress exponent of 8.5 (strain rate sensitivity; m ∼ 0.12). This stress exponent is higher than what is usually observed in Al and Al–Mg alloys under similar experimental conditions. This high stress exponent may arise from the presence of threshold stress that results from dislocation interaction with second phase particles (Mg2Si), precipitating during the deformation at high temperatures. The values of threshold stress showed an exponential increase with decreasing temperature and a dependence with an energy term Qo = 38 kJmol−1. The apparent activation energy for solution treated condition was calculated to be about 320 kJmol−1, which is higher than the activation energy for self-diffusion in Al (Qd = 143 kJmol−1) and for the diffusion of Mg in Al (115–130 kJmol−1). By incorporating the threshold stress in the analysis, the true activation energy was calculated to have a value of 111 kJmol−1, and the normalized strain rates can be represented by a power function of the effective stress with stress exponent of ∼3. Ductility was documented to reveal the best working condition for this alloy in solution treated condition. The ductility exhibited a maximum value of about 120% at 773 K at a strain rate of 0.064 s−1. The results of the current work is, also, compared to the results of another heat treatment condition (T4-naturally aged) to reveal which ever condition holds better hot forming characteristics.

Mg/BN nanocomposites: Nano-BN addition for enhanced room temperature tensile and compressive response

The present study elucidates the effects of nanoscale boron nitride particles addition on the microstructural and mechanical characteristics of monolithic magnesium. Novel light-weight Mg nanocomposites containing 0.3, 0.6 and 1.2 vol% nano-size boron nitride particulates were synthesized using the disintegrated melt deposition method followed by hot extrusion. Microstructural characterization of developed Mg/x-boron nitride composites revealed significant grain refinement due to the uniform distribution of nano-boron nitride particulates. Texture analysis of selected Mg-1.2 boron nitride nanocomposite showed an increase in the intensity of fiber texture alongside enhanced localized recrystallization when compared to monolithic Mg. Mechanical properties evaluation under indentation, tension and compression loading indicated superior response of Mg/x-boron nitride composites in comparison to pure Mg. The uniform distribution of nanoscale boron nitride particles and the modified crystallographic texture achieved due to the nano-boron nitride addition attributes to the superior mechanical characteristics of Mg/boron nitride nanocomposites.

Effects of graphene and CNT on mechanical, thermal, electrical and corrosion properties of vinylester based nanocomposites

Abstract Vinylester nanocomposites with graphene and carbon nanotubes were investigated regarding thermal and viscoelastic behaviour, flexural properties, hardness, scratch resistance and electrical conductivity. The latter showed a percolation threshold for the graphene nanocomposites at ∼2 wt-%, whereas the nanotube system exhibited this transition at 0·03 wt-%. Investigations (SEM) by charge contrast imaging demonstrated a high degree of dispersion of both fillers, with the formation of a continuous percolation network. Quantitative tests regarding the corrosion resistance revealed that the conductive hybrid composites, applied as a coating to a metal substrate, exhibited a better performance than the neat vinylester.

Reinforcing Low-Volume Fraction Nano-TiN Particulates to Monolithical, Pure Mg for Enhanced Tensile and Compressive Response

Novel Mg (0.58, 0.97, 1.98 and 2.5) vol. % TiN nanocomposites containing titanium nitride (TiN) nanoparticulates of ~20 nm size are successfully synthesized by a disintegrated melt deposition technique followed by hot extrusion. Microstructural characterization of Mg-TiN nanocomposites indicate significant grain refinement with Mg 2.5 vol. % TiN exhibiting a minimum grain size of ~11 μm. X-ray diffraction studies of Mg-TiN nanocomposites indicate that addition of up to 1.98 vol. % TiN nanoparticulates aids in modifying the strong basal texture of pure Mg. An attempt is made to study the effects of the type of titanium (metal or ceramic), size, and volume fraction addition of nanoparticulates on the microstructural and mechanical properties of pure magnesium. Among the major strengthening mechanisms contributing to the strength of Mg-Ti-based nanocomposites, Hall-Petch strengthening was found to play a vital role. The synthesized Mg-TiN nanocomposites exhibited superior tensile and compression properties indicating significant improvement in the fracture strain values of pure magnesium under loading. Under tensile and compression loading the presence of titanium (metal or ductile phase) nanoparticulates were found to contribute more towards the strengthening, whereas ceramics of titanium (brittle phases) contribute more towards the ductility of pure magnesium.