Saad M. Aldousari

Cell and nanoparticle transport in tumour microvasculature: the role of size, shape and surface functionality of nanoparticles

Through nanomedicine, game-changing methods are emerging to deliver drug molecules directly to diseased areas. One of the most promising of these is the targeted delivery of drugs and imaging agents via drug carrier-based platforms. Such drug delivery systems can now be synthesized from a wide range of different materials, made in a number of different shapes, and coated with an array of different organic molecules, including ligands. If optimized, these systems can enhance the efficacy and specificity of delivery compared with those of non-targeted systems. Emerging integrated multiscale experiments, models and simulations have opened the door for endless medical applications. Current bottlenecks in design of the drug-carrying particles are the lack of knowledge about the dispersion of these particles in the microvasculature and of their subsequent internalization by diseased cells (Bao et al. 2014 J. R. Soc. Interface 11, 20140301 (doi:10.1098/rsif.2014.0301)). We describe multiscale modelling techniques that study how drug carriers disperse within the microvasculature. The immersed molecular finite-element method is adopted to simulate whole blood including blood plasma, red blood cells and nanoparticles. With a novel dissipative particle dynamics method, the beginning stages of receptor-driven endocytosis of nanoparticles can be understood in detail. Using this multiscale modelling method, we elucidate how the size, shape and surface functionality of nanoparticles will affect their dispersion in the microvasculature and subsequent internalization by targeted cells.

Effect of agglomeration and dispersion on the elastic properties of polymer nanocomposites: A Monte Carlo finite element analysis

Abstract Owing to their superior mechanical and physical properties, carbon nanotubes (CNT) seem to hold a great promise as an ideal reinforcing material for composites of high-strength and low-density. In most of the experimental results up to date, however, only modest improvements in the strength and stiffness have been achieved by incorporating carbon nanotubes in polymers. In the present paper, the influence of single wall carbon nanotube agglomeration on the effective stiffness is analyzed by using an Eshelbys inclusion model. Analytical expressions are derived for the effective elastic stiffness of single wall carbon nanotube-reinforced composites with the effects of agglomeration. The present study not only provides the important relationship between the effective properties and the morphology of CNT-reinforced composites, but also may be useful for improving and tailoring their mechanical properties. In addition, a multiscale Monte Carlo finite element method (MCFEM) was used for determining mechanical properties of polymer nanocomposites (PNC) that consist of polymers reinforced with single-walled carbon nanotubes (SWCNT). Specifically, the method uses a multiscale homogenization approach to link the structural variability at the nano/micro scales with the local constitutive behavior. Subsequently, the method incorporates a FE scheme to determine the Youngs modulus and Poisson ratio of PNC. The use of the computed properties in macroscale modeling is validated by comparison with experimental tensile test data.

Fatigue Life Behaviour of Nanocomposite Coated Carbon Steel

Abstract Recently, nano-materials have received increasingly more attention for their potential applications as structural and functional materials. The unique mechanical properties of CNTs, their high strength and stiffness and the enormous aspect ratio provide potentials for the improvement of the mechanical properties of structural materials. The aim of this research is to investigate experimentally the effect of nanocomposite coating on the fatigue life of carbon steel AISI 1045 specimens with different surface finishes. Nanoadhesives of epoxy resin are synthesized and evaluated. They are originally modified by multiwalled carbon nanotubes (MWCNT) with 0.5 wt.-% as reinforcement. Fatigue tests are conducted on the respective specimens by a rotating bending machine of the cantilever type. Comparing the results for specimens coated with 0.5 wt.-% MWCNT-epoxy composition with the base materials it is found that fatigue life increased five times for a roughness of 0.3 µm and three times for an average specimen roughness of 0.8, 1.6 and 2.5 µm, respectively.

Material optimization of a cemented tibia tray using functionally graded material

Abstract Joint replacement surgeries are doubtlessly the gift of science and technology for human welfare. In the cemented knee replacement joint, the stiffer implant carries the majority of the load, which is actually carried by the bone itself before implantation. The resulting implant induced stress-shielding and subsequent bone remodeling causes bone resorption at the proximal bone under the tibia tray. The aim of this study is to optimize the material of the cemented tibia tray using functionally graded material FGM. The target is to find the optimal material and the optimal gradation direction for the cemented tibia tray. The results showed that the optimal vertical FGM changed from titanium at the lower tibia stem to bioglass at the upper layers of the tibia tray. The vertical FGM reduced the stress shielding by 56 and 80 % in cancellous epiphyseal and diaphyseal bone, respectively, compared to cemented titanium tibia tray. However, the optimal horizontal FGM changes from titanium at the stem core to bioglass at the rim of tibia tray layers. This horizontal gradation reduced the stress shielding in cancellous epiphyseal bone by 62 %. However, the stress shielding in cancellous diaphyseal bone did not change compared to cemented titanium tibia tray.

Effect of Nanocomposite Coating with Different Concentrations on the Fatigue Life of Stainless Steel316 with Different Surface Roughness

Abstract Many experimental researches succeeded to improve fatigue properties of materials by treating their surfaces. In this study, the benefits of nanocomposite material are used to investigate the fatigue life of stainless steel specimens with different surface roughness. Nanocomposite coating was prepared with different concentrations (0.3 %, 0.5 %, and 0.7 %) of multi wall carbon nano tubes MWCNT. This coating was applied on stainless steel test specimens with four different values of the surface roughness (0.3, 0.8, 1.6, and 2.5). It turned out that fatigue life increased more than four times compared to the original material when using 0.5 % and 0.7 % MWCNT concentration in coating composition with the 0.3 surface roughness, while no significant difference was detected at another roughness.

Design Optimization of an Automobile Connecting Rod Using FEM

Abstract In automotive engines, the connecting rod is subjected to high cyclic loads. These are represented by high compressive loads due to combustion, and high tensile loads due to the connecting rod mass of inertia. The main objective of this study is to optimize the shape of a connecting rod in an automobile engine. A model of the connecting rod has numerically been built and has been solved by the Finite Element Method (FEM) using the ANSYS package to determine the stresses distribution over the entire rod. In addition, the transition force analysis of the connecting rod and the verification of the analysis are shown. The aim of the optimization has been to minimize the respective Von Mises stresses which occur at connected rod in both cases, i. e. compressive loads coming from the gas pressure at maximum engine output and the bending loads resulting from the inertia force at the maximum engine power. The weight of the connecting rod should be maintained to prevent increasing of the inertia force. The results of this study indicate that the maximum compression stress occur at compressing loads at the small end section of the connecting rod. Optimizing the radius at the small end decreases such stresses. On the other hand, the inertia forces of the connecting rod mass cause a maximum bending stress at the large end section. By changing the shape and geometry of this section the maximum Von Mises stresses are reduced by 16.5 %, as compared to the original design. A buckling analysis has been carried out for the original and the optimized model and the results have been compared. The load factor (critical load / applied load) is increased by 7 % compared to the original design. Finally, a shape optimization for connecting rod reduces the stresses over the entire rod.

Material Composition Optimization of FGM Plates Containing a Hole

Abstract By definition, Functionally graded materials (FGM) are new advanced composite materials which are used to produce components featuring engineered gradual transitions in microstructure and/or composition. FGMs permit tailoring of material composition so as to derive maximum benefits from their inhomogeneity. The aim of the study behind this contribution is to optimize the composition variation between the ceramic and the metal in order to minimize the maximum stress concentration around the hole in a plate made of FGMs in case of the plate is subjected to pressure, heating or both pressure and heating. The finite element method (FEM) has been used to optimize the material composition of functionally graded materials made from Al 1100 as the metal portion and SiC as the ceramic portion using the ANSYS package. The objective has been to minimize the stress concentration factor around a hole in a plate expressed by the ratio between the principal stress calculated by the ANSYS and the applied stress at different volume fractions of the metal and the ceramic. The investigations have shown that when applying pressure or heating to the plate the optimum for minimizing the stress concentration is to have a ceramic-rich plate and when the plate is subjected to both pressure and heating the optimality is to have a metal-rich plate.

Comparison of titanium and FGM dental implants with different coating types

Abstract Despite their proven record in promoting osseointegration, titanium and titanium alloys present certain other challenges to providing an optimal dental implant. Titanium and suitable titanium alloys have a higher stiffness than human bone, and therefore dental implants formed from such materials absorb most of the forces of mastication. This can lead to a phenomenon known as a stress shielding of the surrounding bone. A variety of bioceramics have been developed and used in different implants due to their excellent biological performance. However, only a few of them have been used in clinical applications, especially in low load bearing implants, due to their poor mechanical strength. Little existing research has been reported for the design of dental implants made of FGM materials. However, many researchers have studied the effect of improving the dental implant surface by coating its surface with different materials including functionally graded materials (FGM). On the other hand, the effect of coating the FGM dental implant with a homogenous material has not been studied yet. The main goal of this work is to compare the biomechanical behavior of three types of dental implant models. Three dimensional models are created. The first model is a homogenous dental implant with a homogenous coating material. The second model represents a homogenous dental implant with a FGM coating and. the third model is a functionally graded implant with a homogenous coating material. The FGM implant with homogenous coating appears as the most suitable model. It reduces the bone stress on cancellous bone by 4.6 % and by 6.5 % on cortical bone compared to homogenous implant with homogenous coating. This leads to reduction of bone stress shielding as well as reduction of the aseptic loosening of bone/implant/coating interfaces which increase the life time of the implant.

Influence of different nanomaterials on the mechanical properties of epoxy matrix composites

Abstract Carbon nanotubes (CNTs) and other nanoparticles such as silicon carbide (SiC), alumina (AL2O3) are used to improve the material properties of polymers and in general are considered to be highly potential fillers. However, questions concerning the proper type and amount of CNTs, e. g., single-wall CNTs (SWCNT), double-wall CNTs (DWCNT), or multi-wall CNTs (MWCNT) and other nanoparticles such as silicon carbide, alumina and their influence are still to be answered. This work studies the effect of the amount and types of nanofillers on the mechanical properties of epoxy based nanomaterials and their functionalization. In the present work, epoxy resin was modified with different types of nanofillers including SWCNT, DWCNT, MWCNT, SiC and AL2O3. The amount of CNTs (SWCNT, DWCNT and MWCNT) used for each type of CNTs were 0.1, 0.3 and 0.5 wt.-%. By contrast, the amount used for (SiC), and (Al2O3) measured 0.5, 1 and 1.5 wt.-% for each type. Tensile test were conducted for each group to investigate the mechanical properties of epoxy based nanomaterials. The results show that CNTs of 0.3 wt.-% is optimal compared with other amounts, e. g. 0.1 and 0.5 wt.-%. The tensile strength at 0.3 wt.-% SWCNT/E, DWCNT/E and MWCNT/E increased by 44 %, 37.4 % and 35.9 %, respectively compared to the neat epoxy. For (SiC), and (Al2O3), the results show that an amount of 1.5 wt.-% is optimal compared with other amounts, e. g. 0.5 and 1 wt.-%. The tensile strength at 1.5 wt.-% for Sic/epoxy and Al2O3/epoxy nanocomposite increased by 25 %, and 43 %, respectively compared to the neat epoxy. Finally, the results show that the (SWCNT) is optimal compared to the other nanofillers.

Estimation of the mechanical properties of nanocomposites based on the properties prediction of single wall carbon nanotubes (SWCNT)

Abstract A finite element model has been developed based on molecular mechanics to predict the mechanical properties of single wall carbon nanotubes (SWCNT). In addition, the mechanical properties of nanocomposite were investigated analytically and experimentally. This work consists of three parts; the first part is prediction of Youngs modulus of single wall carbon nanotubes by molecular mechanics based finite element modeling. The second part describes the experimental work. The third part deals with the validation of the analytical part and the experimental work. The mechanical properties of SWCNT were obtained from FE. The mechanical properties of neat epoxy were experimentally determined. Both of them were used to estimate the mechanical properties of SWCNT/epoxy nanocomposite analytically. A comparison between the analytical and experimental results of SWCNT/epoxy nanocomposite has been done. The modeling and analysis of (SWCNT) were carried out using FEM by MATLAB and ANSYS software. However, in the experimental work the epoxy resin was modified by adding SWCNT with different ratio, i. e. 0, 0.1, 0.3, 0.5 and 0.7 wt.-%, respectively. The materials were characterized in tension to obtain the mechanical properties of SWCNT/epoxy nanocomposite experimentally. The results from the FE model were compared with the results in the literature and good agreement was achieved. The FE approach is a valuable tool for studying the mechanical behavior of carbon nanotubes. The results show that a nanotube weight percent of 0.3 wt.-% of SWCNT improves all mechanical properties such as tensile strength, modulus of elasticity and toughness. The weight percent greater than 0.5 wt.-% SWCNT should be avoided. To predict the mechanical properties of the composite materials analytically, it is worth considering the conventional rule of mixtures using the reasonable nanotube volume fractions and exact value of the efficiency parameter.