Mechanical engineering- material science- composite materials

The effect of cerium addition on wear behaviour of ascast Al-4Si-4Mg alloys has been studied. Dry sliding wear tests were performed against a hardened carbon steel (Fe-2.3%Cr-0.9%C) using a pin-on-disc configuration with fixed sliding speed of 1 m/s and a range of load 10 N, 30 N and 50 N at room temperature (25 o C). Morphologies of both worn surfaces and collected debris were characterised by a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDX). It was revealed that 1 -5 wt% of cerium addition resulted in the formation of intermetallic phase Al-Ce and Al-Si-Ce. The increase of cerium content in the alloy led to higher wear resistance behaviour for ascast alloys. Formation of craters and localised plastic deformation were observed on the worn surface of the alloys, resulting fine particulate and sheet-like wear debris. The change in morphology of the wear debris was also found consistent with the change in worn surface appearance.

The work presented in this article is directed towards the application of CFRP foam core sandwich structures as primary structures in commercial aviation. With closed cell rigid foams, it is possible to produce comparatively low priced high-integral sandwich components having a complex geometry in terms of a curved and a variable lateral cut. Sandwich structures are offering a good bending stiffness and strength to weight ratio. Thus, they are suited for using in structures which are at risk to fail by buckling. The investigations are focused on a CFRP sandwich structure with polymethacrylimide (PMI) foam core, named ROHACELLRIST. Besides good structural stability at thermal conditions, the foam is characterized by a good strength and stiffness to weight ratio. Primary structures in aircraft applications are exposed to a superposition of in-service loads and environmental conditions. The typical working loads in combination with environmental conditions were investigated. The structure needs a sizing with respect to large temperature changes and influences of humidity. Thus, the time, temperature, and moisture dependency of the mechanical behavior were studied for the single components of the structure and for the composite itself. Therefore, Finite Element Models on macroscopic level were built with reference to the experiments. For each in-service case, the residual stresses arising during manufacturing have to be regarded and quantified. During manufacturing, the sandwich structure is cured at 180C. Due to the different stiffnesses and coefficients of thermal expansion of the foam and the CFRP face sheets, residual stresses are induced by cooling down to service temperature. Among others, some tests were made at laterally closed CFRP sandwich structures with a storage time up to half a year at certain climate conditions. The aging process is not only controlled by external conditions, but also by a rearrangement of molecules, for example, the relaxation behavior of the PMI foam. Another question of the long-term behavior of the CFRP foam core sandwich structure is the characteristic of delamination of the face sheets from the inner core after an impact has occurred. To describe the crack growth behavior of the sandwich structure fracture mechanical principles can be used estimating the damage tolerance. Sandwich specimens with initial damage were loaded up to 3 million mechanical load cycles.

Necessity of resource is increasing due to continuously increase in World population and rapid 15 industrialization, while natural resources are getting exhausted day by day. Usage of waste 16 materials or by-products in highway constructions has substantial environmental and economic 17 benefits. In this study, the usage of cullet and waste glass bottle dust as mineral filler material in hot 18 mix asphalt alternate to traditional crushed stone dust were investigated. Optimum bitumen content 19 was determined by Marshall Mix Design Method by using 6 different bitumen contents (4.0, 4.5, 20 5.0, 5.5, 6.0, and 6.5%). With the optimum bitumen content, 3 different mineral filler type (cullet, 21 glass bottle waste and stone dust) and 6 different filler ratios (4, 5, 6, 7, 8 and 9%) were used to 22 prepare asphalt mixture samples. Samples were performed by Marshall Stability test and the results 23 were compared. It is concluded that cullet and glass bottle waste can be used in asphalt mixtures as 24 mineral filler alternate to crushed stone dust if the economic and environmental factors are in favor. highway constructions and road layers from top to subgrade. Higher performance and 37 environmental friendly road pavements can be constructed by the use of by-products instead of 38 traditional materials [1]. 39 40

Components press formed from layered or laminated metallic materials have wide engineering application in aerospace, automobile, electrical, electronic and process industries. High strength ferrous metals are widely used in automobile industries for utilization of its high strength to weight ratio. Such high strength metals offer poor formability. Formability of such metals can be improved by applying a layer of metal having higher formability. This paper deals with springback behavior of a laminated stainless steel and aluminum in
V bending. Investigation of bending characteristics like thickness ratio and bending angles of sheet before/after springback is carried out in this paper. First part of this paper is on numerical analysis for springback prediction of laminated sheet. In second part, experiments are performed for different cases on V bending machine. The experimental results show that springback of sheet metal laminate is greatly affected
by relative position of strong/weak layers and thickness ratio of each layer.

Regenerator is very important part of the desiccants dehumidifier system. It is used to regain the concentration of the solution by removing the moisture from the solution so that it can be reuse. The celdek pads as packing material and lithium bromide as the desiccant has been used in the regeneration system. The counter flow of air and desiccant solution is selected in the current research paper. The effect of solution flow rate and air inlet temperature  will be studied on different outlet parameter; the evaporation rate, regenerator effectiveness, out let dry bulb temperature of the air, %age change in the concentration and solution outlet temperature The results show that there is increment in the evaporation rate and regenerator effectiveness with increase these inlet parameters.

Determining the efficiency and performance of polymer formulations used as consolidants for fragile, multilayered decorative coatings is often a great challenge in conservation. This paper reports the results of tests that investigated the performance of a variety of consolidants for the stabilization of such coatings. East Asian lacquer coatings were used as a typical representative of multilayered coatings with protein-bound (gesso-type) foundation layers that show brittle fracture, delamination, and flaking. Mechanical strength tests were undertaken with a fracture mechanics approach using the standardized double cantilever beam (DCB) method. The independent material property fracture energy, GIc, was measured, and the fracture behaviour of the brittle, protein-bound foundation layers was determined. DCB specimens were prepared, fractured, then consolidated with a variety of polymer formulations and re-fractured to provide data for direct comparison. The tested consolidants inclu...

Manufacturing Firms sometimes suffers from Productivity, Low Production rate and Delivery
problems. Production time is the top priority at every manufacturing firm, and each firm wants to
minimize it as much as possible to deliver their product on time to time their valuable customers. .
Some of the biggest time eaters in the industry are Setup time, Manufacturing time, Material
handling time, and wait time. After the brief survey at VBC Hydraulics, we have conclude that
setup time, manufacturing time, and wait time can not be utilize more than current because they
are already using best possible machines and technology to manufacture Gear Pumps. But,
material handling time and man-machine utilization can be improved by some engineering
analysis. We did man-machine utilization by using man-machine utilization charts and some brief
calculations and also focused to improve the material handling in the industry by implementation of GT(Group Technology) layout as they are mainly focused to manufacturing of Gear Pumps of different specifications with bulk Production.

Hazard Identification, Risk Assessment and Determining Control (HIRADC) is part of the standard OHSAS 18001:2007 clause 4.3.1, which is the organization shall establish implement and maintain a procedure for ongoing hazard identification, risk assessment and determination of necessary controls. This was a HIRADC report for a specific operation process at Solar Company that was obtained by conducting the risk assessment together with the fellow subordinates. Based on hazard identification analysis on operation area, it was revealed 10 potential hazards which are the physical hazard, radiation and chemical hazard. Found out the total risk level score without control was at medium level for all the activities except on hazard no 9 which on lower level. After the risk assessment taken place and all the necessary control measure were carried out all the activities have fallen into low risk level category which are at level 1 and 2.

Austenitic Stainless steel (316L) is a low carbon high chromium containing high alloy steel, it has a good number of application because of its high strength, high ductility and corrosion resistance. It is used in jet engine parts, heat exchanger application and pharmaceutical application. It is compatible in cryogenic temperature to red hot temperature. The paper presents an experimental investigation on different parameters which affect the cutting process and also cause significant effect on the chip formation in machining of Austenitic Stainless steel (316L). In this study, experiments were conducted on Austenitic Stainless steel (316L) at different cutting speed, feed and depth of cut and the effect of different influential parameters on the process of chip formation has been studied subsequently. Quality characteristic of machined item is depending much on material behaviour during machining. Present experimental analysis on machining has been performed by implementing Von Mises stress evaluation employing true stress-true strain behaviour of the materials under consideration. Experimental true stress-true strain plot was required to find out the strength coefficient and strain hardening exponent of the material and using the same, Von Mises stress was estimated by using material property consideration. Experimental study on machining was performed on austenitic stainless steel (316L) to know the trend of variation of chip thickness, shear angle, Von Mises stress and total work done with respect to cutting velocity. From the study it showed that austenitic stainless steel gets work hardened at higher cutting speed. Therefore this type of material can be machined at lower cutting speed only.

The corrosion behaviour of 6082 aluminium alloy was studied by measuring the
electrochemical impedance spectra and electrode polarization curves. After the
electrochemical tests, a microstructural analysis of the samples was conducted
by using optical microscopy and electron scanning microscopy techniques to
determine the corrosion mechanism. The results show that the Nyquist plot of
the electrochemical impedance data in the NaCl solution consists of high‐ and
low‐frequency capacitive impedance loops. When SO24− ions are added to the
NaCl etchant, the Nyquist plots of the electrochemical impedance data are
composed of two different curves: a high‐frequency capacitive impedance loop
and a low‐frequency inductive impedance loop. The corrosion current density
increases with increasing SO24− concentration, and as a result, the corrosion
resistance of the aluminium alloy decreases. The microstructures of 6082
aluminium alloy consist of Mg2Si secondary particles in a large α‐Al matrix.
Pitting corrosion initially occurs at the boundary between the matrix and
secondary particles because the electrode potentials of the matrix and secondary
particles are different. Then, corrosion paths develop along the network‐like
grain boundaries, and finally, massive network‐like corrosion occurs throughout the entire alloy.

The effects of particle size and polymer location (core or shell) on the mechanical properties of core/shell materials composed of polystyrene (PST) and poly(butyl acrylate) (PBA) made by a two-stage emulsion or microemulsion polymerization process are reported. Low-seed content (LSC) latexes were made by batch polymerization in microemulsions stabilized with DTAB in the presence of an organic salt (dibutyl phosphite). High-seed content (HSC) latexes were produced by microemulsion or emulsion polymerization in semi-continuous process. These latexes were subsequently used to form core/shell particles of PST/PBA or PBA/PST and their mechanical properties were examined and compared.

Sandwich structures with face sheets made of carbon fiber reinforced plastics (CFRP) demonstrate a high potential to reduce both production costs and the weight of primary aircraft structures. This potential has however yet not been realized mainly due to the complex structural and material behavior of sandwich structures under different kinds of loading and adverse effects like moisture take up of honeycomb core material [1]. Using closed cell hard foams such as PMI foam, better known as Rohacell®, the issue of moisture take-up has been solved. One more critical issue however is the often criticized lack of damage tolerance of sandwich structures [2].
Impact damage resistance is part of the larger topic of damage tolerance. It can be treated separately as impacts may cause a damage that is used a starting point for a damage tolerance analysis while not vice versa. In consequence the resulting damage size of a predefined impact scenario is of great importance.

As is well known, repair, rehabilitation and strengthening of old concrete or seismically vulnerable structures is a technique that is used very often in order to extend the operational life of buildings and concrete structures. Such techniques are usually based on traditional, often inefficient techniques and on conventional materials, which may soon exhibit new durability problems. For structural upgrading, reinforced concrete jacketing and surface-bonded steel plates are mostly used. However, during the last decades high-performance advanced composites of the type routinely used in aerospace, such as carbon fibre reinforced plastics, are entering the stage, despite their much higher material costs. In the present work different methods of repairing, using CFRP laminates, of a concrete beam having a center crack are discussed analytically. The stresses and the deformations calculated are analytically discussed and the different repairing methods are evaluated systematically. Problems concerning the dynamic characteristics of the repaired structures are also presented, and a new approach for the repair strategy is introduced.

Preparation and characterization of aluminum metal matrix composites reinforced with aluminum nitride was carried out. A graphite crucible and a stainless steel permanent mould was used to prepare the samples. An optimum stirring speed was determined for a fixed stirring time before cast in the permanent mould. Morphology of the composite and particle distribution were investigated by optical microscopy. The reinforcing particles were clearly shown present at the edges and around grains of silicon primary, silicon needles and inter-metallic compound of FeMg 3 Si 6 Al 8. The result of hardness test was 44 Hv for Al-Si matrix and increased to 89 Hv for an Al-Si composite reinforced with 5% wt.% AlN powder. The higher values in hardness indicated that the AlN particles contributed to the increase of hardness of the matrix.

Within the work, on the basis of previously obtained real components, the design, dimensioning and analysis of hexacopters were performed. The 3D virtual model was developed using the SolidWorks software package, and then the necessary stress analysis by the finite element method was performed. After 3D modeling, an analytical load calculation was performed on the hexacopter landing and take-off mechanism. During the calculation, real loads were used during the landing and take-off of the hexacopter. After the analytical calculation, a numerical analysis was performed using the finite element method, where the mechanisms for landing and taking off hexacopters were observed separately. In FEM analysis, the principal stresses at characteristic places were observed, as well as displacements or deformations on the take - off mechanism. After that, a comparison of analytical calculation and numerical (FEM) analysis of the hexacopter structure was performed. On that occasion, a good match between the results of these two methodswas established, which verified the numerical method used.

Synthetic refrigerant has better characteristic and technical properties compared to hydrocarbon refrigerant, odorless, non-toxic, easy to get and affordable price. However, hydrocarbon refrigerant is environmentally friendly but flammable material. The objective of this research was to determine the refrigeration capacity as affected by pressure and temperature change at evaporator and condensor towards the power consumed by compressor. As resulted from measurement and simulation, the temperature occurred at evaporator and condenser and also the power consumption of compressor increased while the refrigeration capacity decreased. This condition reduced the coefficient of performance of vapor compression heat pump system. The optimum power of vapor compression heat pump system using R134a occurred at condenser temperature was 59 oC. The largest coefficient of performance for refrigeration and heating was 3.04 and 4.21, respectively with refrigerant mass flow rate was 0.00673 kg/s

For certain medical applications such as bone and teeth implant it is required to fabricate certain bio-composite materials that are compatible with natural human organs. This paper is primarily focused on the theoretical design and analysis of a set of two natural bio-composites made of Hydroxide Apatite (HA) as ceramic matrix. Two fillers of Titanium (TI) metallic powder and Polyamide 6 (PA 6)  will be used as reinforcements respectively. The analysis will be based on two mechanical and one physical property of the bio-composites including strength (σ) ,Young’s modulus (E) and composite density (ρ), at fibre volume fractions ranging from 0-50 % respectively, using two well-known comparative methodologies as Rules of Mixture (ROM) and Halpin-Tsai (HPTS) for each bio-composite independently.

An epoxy resin (EP) matrix has been modified with depolymerized natural rubber (DNR). The 0.5, 1.0, 1.5, 2.0, and 2.5 wt% DNR-filled epoxy were used for the present investigation. The primary aim of this development is to scrutinize the mechanical properties of such cured epoxy filled with DNR. When the rubber content was low, the mechanical strength was low and the free volume of DNR in epoxy matrix was less. With the increase in rubber content, the free volume of rubber in the composite increases and the mechanical strength increases; however, after a specific weight percentage of rubber, if we increase the amount of rubber, the mechanical strength decreases and the free volume of rubber in the composite increases quickly, but with the increase in DNR weight percentage in epoxy matrix, the hardness decreases. The scanning electron microscopy (SEM) results justified the results obtained from the mechanical tests.

Plate and shell analysis using classical plate theory (CPT) has a lack of accuracy in predicting the influence of transverse deformation, because of its assumption that the line normal to the surface remains straight and normal to the midplane before and after deformation. The next revision by constant shear deformation theory or famous as first order shear deformation theory (CSDT/FOSDT) still suffers a disadvantage that has a constant value in the shear term that is called shear locking phenomenon. This matter has been corrected by higher order shear deformation theory (HOSDT) using a refined assumption that the line normal to the surface should be in a parabolic function and not normal to the midplane, but normal to the surfaces so that it fulfills the zero strain in the surface. The analysis of the bending part of laminated composite flat shell element is applied by higher order lamination theory (HOLT) that is adopted from HOSDT. This model is accurate for thicknesses variation and complex materials. HOLT model is implemented into finite element procedure to find deflection, stresses and internal forces. It can be concluded that the displacement and stresses in HOLT model are higher than FOLT the ones (first order lamination theory) in small ratio of a/h dan its result almost the same value for a/h ratio more than 10. In a square plate case, the displacement gets smaller if the fiber arranged into cross-ply sequence. Interlaminar stresses along the thickness is not distributed continuously, but they have certain modes that depend on the depth of point position, the lamina or layer number, fiber orthotropic angle of each layer and a/h ratio.

Determining the efficiency and performance of polymer formulations used as consolidants for fragile, multilayered decorative coatings is often a great challenge in conservation. This paper introduces a new application of the standardised double cantilever beam (DCB) test method used in fracture mechanics as an improved means to tackle this problem. The adapted DCB method was employed to determine the independent material property fracture energy, GIc, and the fracture behaviour of brittle, protein-bound (gesso-type) foundation layers on wooden substrates that typically suffer from delamination and flaking. DCB specimens containing the brittle foundation layer between wooden beams were prepared. Once fractured, the specimens were consolidated with different polymer formulations and re-fractured to provide data for direct comparison. The results showed that the method could determine measurable differences in fracture energy, and also supply valuable and detailed information on change...

Various nano- and micro-sized fillers can be integrated into polymers to enhance their flame-retardant performance. In this work, a diglycidyl-ether bisphenol A epoxy was used as the matrix and nanostructured silica aerogel (AG) and ammonium polyphosphate (APP) microparticles were investigated as fillers to improve the flame-retardant and thermal properties of the epoxy. The anti-flame, thermal, and mechanical properties of the composites were investigated for different volume fractions of filler particles. It was found that APP decreased the burning rate while significantly improving the thermal stability. To investigate the flame resistant properties of combined AG and APP, an optimized ratio of AG and APP was added to the epoxy, leading to a stable flame-retardant epoxy with a low thermal conductivity and improved glass transition temperature (Tg). The synergy between the AG and APP in composite samples resulted in an interesting burning behavior where sample core was relatively ...

Damage following static indentation of jute/hemp (50 wt.% total fiber content) hybrid laminates was detected by a number of nondestructive testing (NDT) techniques, in particular, near (NIR) and short-wave (SWIR) infrared reflectography and transmittography, infrared thermography (IRT), digital speckle photography (DSP), and holographic interferometry (HI), to discover and evaluate real defects in a laminate with a complex structure. A comparative study between thermographic data acquired in the mid- (MWIR) and long-wave infrared (LWIR) spectrum bands, by pulsed (PT) and square pulse (SPT) thermography, is reported and analyzed. A thermal simulation by COMSOL

The distribution of stresses in laminated composite plates with a central circular hole and having various stacking sequences, different geometric dimensions and subjected to in-plane axial tensile loading was investigated. The ANSYS computer program was utilized using the finite element method to study the linear and nonlinear material effects. A new method was proposed for the purpose of incorporating the material nonlinearity model into the ANSYS computer program using the secant modulus material model. The aim of the authors is to analyze the effect of

This study aims to investigate the moisture absorption of recycled newspaper fiber and recycled newspaper-glass fiber hybrid reinforced polypropylene composites to study their suitability in outdoor applications. In this work composite materials were made from E-glass fiber (G), recycled newspaper (NP) and polypropylene (PP), by using internal mixing and hot-pressing molding. Long-term water absorption (WA) and thickness swelling (TS) kinetics of the composites was investigated with water immersion. It was found that the WA and TS increase with NP content in composite and water immersion time before an equilibrium condition was reached. Composites made from the NP show comparable results as those made of the hybrid fiber. The results suggest that the water absorption and thickness swelling composite decrease with increasing glass fiber contents in hybrid fiber composite. It is interesting to find that the WA and TS can be reduced significantly with incorporation of a coupling agent (maleated polypropylene) in the composite formulation. Further studies were conducted to model the water diffusion and thickness swelling of the composites. Diffusion coefficients and swelling rate parameters in the models were obtained by fitting the model predictions with the experimental data.

The use of fiber-metal laminates (FML) allows for substantial advantages over a fuselage skin made of monolithic aluminum materials. Glass fiber prepreg reinforced aluminium is characterized by high damage tolerance capabilities, supporting the structural strength capability in case of any kind of damage. For this reason, FML, and GLARE in particular, have been identified as superior materials for aerospace applications. More than 400m2 FML is applied on each A380, as skin panels and as D-noses for both, vertical and horizontal stabilizer. FML possess the potential to become the baseline material for next-generation single-aisle aircrafts [1, 2, 6]. The development of a new production chain that will allow automated fuselage production for future short-haul aircrafts is the focus of the studies that make up the joint project AUTOGLARE. As part of the fifth call-up for the German Aeronautical Research Programme (LuFo), the German Aerospace Center (DLR) is working with its project par...

This work focuses on identifying the thermal conductivity of composites loaded with phase-change materials (PCMs). Three configurations are studied: (1) the PCMs are divided into identical spherical inclusions arranged in one plane, (2) the PCMs are inserted into the matrix as a plate on the level of the same plane of arrangement, and (3) the PCMs are divided into identical spherical inclusions arranged periodically in the whole matrix. The percentage PCM/matrix is fixed for all cases. A comparison among the various situations is made for the first time, thus providing a new idea on how to insert PCMs into composite matrices. The results show that the composite conductivity is the most important consideration in the first case, precisely when the arrangement plane is parallel with the flux and diagonal to the entry face. In the present work, we are interested in exploring the solid-solid PCMs. The PCM polyurethane and a wood matrix are particularly studied.

The present study investigates the influence of graphene nanopellets (GnPs) on the damping and vibration characteristics of fiber-reinforced basalt/epoxy composites for different weight contents of GnPs particles (0.1, 0.2 and 0.3 wt%). The variation of dynamic properties in terms of loss and storage modulus was explored by using the experimental modal analysis. The damping properties were determined by using logarithmic decrement method from the acceleration-time envelope curves. Results showed that the incorporation of GnPs at weight contents of 0.1% and 0.2% significantly affected the damping and vibration characteristics of the samples as a result of the interfacial strength between the GnPs particles-fiber-matrix interactions. The natural frequencies increased by 20.7% and 25% at GnPs contents of 0.1 and 0.2 wt%, whereas the damping ratios increased by 28.5% and 57.1%, respectively.

In the present work, the effects of adding nanoalumina and marble dust on the wear behavior of dental composites were investigated. The hardness of dental composite was determined using Vickers micro-hardness tester. A two-body abrasive wear test was performed on the dental wear simulator under the medium of artificial saliva. The experiments were performed as per the Taguchi orthogonal array and steady state condition by varying parameters such as filler content, normal load, sliding velocity, and number of cycles. The hardness results indicated that the incorporation of 5 wt. % of nanoalumina increased the hardness of the dental composite by 12%, whereas the incorporation of 5 wt. % of marble dust increased the hardness of the dental composite by 7%. Also, for the experiments as per the Taguchi orthogonal array, the mean volumetric wear in the case of nanoalumina-filled dental composite was 9.6% less than that of marble dust-filled dental composite. However, in both the cases, the...

The decision on sequencing of operations, tool travel and machining time calculations is done in
microplanning. After a set of processes has been selected for all the features of part, the sequencing task
begins by searching and analysing relationship between features. This is done by rule to detect geometrical
interactions and the appropriate precedence relationship in knowledge base. For deciding sequence of
operations precedence relationship among the different operations is developed using decision rules.
CNC program is generated based on the process plan of a given component. The generated CNC program
is then validated by simulation software before giving it to CNC machine.

Flax fibers can be used as ecological alternatives to conventional reinforcing fibers (e.g., glass) in composites. Flax fibers have some advantages over glass fiber, because they are less dense, renewable, combustible and are relatively low in price. This excellent price-performance ratio at low weight, in combination with the environmentally friendly character is very important for the acceptance of natural fibers in large volume engineering markets. A major restriction to the successful use of natural fibers in durable composite applications is their high moisture absorption and poor dimensional stability. In order to improve the above qualities, various surface treatments of fibers including silane treatment, benzoylation, and peroxide treatment were carried out, to improve mechanical performance of fiber composites. Also, composites consisting of high-density polyethylene (HDPE) or linear low-density polyethylene (LLDPE) or HDPE/LLDPE, chemically treated fibers and additives were prepared by extrusion process. The extruded samples were then ground and test samples were prepared by rotational molding. The chemical analysis showed that selective chemical treatments increased the α-cellulose content of flax fibers from 73% to 95%, but caused a decline in hemicellulose and lignin content. Derivative thermogravimetry (DTG) curves indicated that chemically treated fibers were thermally stable in the region below 250 °C and chemcial treatments increased the onset thermal decomposition temperature of flax fibers. The mechanical properties demonstrated an increase in tensile strength from 17.56 MPa of untreated fiber (20 wt%) reinforced LLDPE to 25.86 MPa of peroxide treated fiber (20 wt%) reinforced LLDPE. The increased hardness of flax fiber-reinforced composites was also very promising; it was 22.1 of untreated fiber (20 wt%) reinforced HDPE compared to 25.1 of silane treated fiber (20%) reinforced HDPE. This increase in fiber content has a positive effect on the mechanical properties of composites. The water absorption of the chemically treated flax fiberbased composites was lower than that of the untreated fiber-based composites.

Sandwich structures with  face sheets made of carbon fibre reinforced plastics  (CFRP) have a high potential in  reducing production costs and  weight of primary  aircraft structures. Their  advantage is based on their superior bending stiffness compared to solid laminates. This allows a less complex and highly integrated structural design which typically reduces the number of parts and joints significantly. The highlighted potential has however yet not been realized within primary aircraft structures mainly due to the complex structural behaviour. Another adverse effect often mentioned is moisture take up of the core material. Using closed cell hard foams such as PMI foam, better known as Rohacell®, for the core, the problem of moisture take-up has been solved. Damage tolerance however has been one of  the most critical  issues regarding the  use of sandwich structures [1]  [2]. Extensive research has been conducted on CFRP foam core sandwich structures with mostly PVC foam for application in marine vessels, which provides a large benefit for today’s level of understanding. Past and current research  concentrates on describing material behaviour with damage, damage growth under cyclic loading  and consequently  maximum  damage  sizes [3]-[5]. Less attention  has however  been given to damage initiation by localized impact events. Low Velocity impact may lead to face sheet
and/or core damages [6]-[8].

Carbon fiber reinforced polymer (CFRP) is widely used in high-tech industries because of its interesting characteristics and properties. This material presents good strength and stiffness, relatively low density, high damping ability, good dimensional stability, and good corrosion resistance. However, the machinability of composite materials is complex because of the matrix/fiber interface, being a challenging machining material. The CFRP milling process is still necessary to meet dimensional tolerances, the manufacture of difficult-to-mold features like pockets or complexes advance surfaces, finish the edges of laminated composites, or drill holes for the assembly of the components. Besides, the demand for low-cost, reconfigurable manufacturing systems of the industry demonstrates that the application of industrial robots (IRs) in the CFRP milling process becomes an alternative for providing automation and flexibility. Therefore, the objective of this work is to evaluate the perfor...

A sliding wear behaviour of several commercial bearing alloys were tested against a hardened AISI 4340 steels at three different sliding distance, 500, 800 and 1500 m. Under a pin-on-disc configuration, the test was performed in a lubricated condition (engine oil) in order to imitate the contact behaviour of a connecting rod and a crankshaft in an engine. In this work, deformations of the bearings were being monitored by an acoustic method via airborne. With frequencies ranging from 0 to 20 kHz, deformed bearing signals were then analysed by MATLAB software including the 3D I-kaz method. It was found that wear coefficient, K' for 500 m sliding speed showed 8.5x10 -5 mm³/Nm and based on FFT analysis a signal was generated during the test done. Thus, it can be concluded that the wear loss can be recorded via airborne which was induced by generated sound from the pin and disc contacts.

Concrete is frequently used in the construction industry because it is readily available and has proven high ductility. A primary component of concrete is cement, the production of which, however, is energy consuming and results in environmental pollutants. Consequently, researchers have begun to use geopolymers as an adhesive with chemical, thermal, or mechanical activators. The use of geopolymers is cost effective and energy saving because it is self-produced from industrial recycling. This research replaces cement with geopolymers to evaluate concrete behavior. Results show that use of geopolymers increases the compressive strength of concrete while lowering the temperature of the concrete environment due to decreased hydration rates.

Abstract
The purpose of the present research work is to study the structural, mechanical and wear properties of artificial hip ceramic composites with varying proportion of aluminum and chromium oxide. The ceramic composites containing fixed amount of zirconium oxide, magnesium oxide, silicon nitride with varying amount of aluminum and chromium oxide were fabricated by using spark plasma sintering process and subsequently evaluated for structural (XRD, X-ray diffraction), elemental (EDS, energy-dispersive spectroscopy), mechanical (fracture toughness, elastic modulus and hardness) and wear properties. The results showed that aluminum and chromium oxide contents have a significant influence on the mechanical and wear properties of the fabricated ceramic composites. In particular, the composites containing 1.5 wt% chromium oxide and 70.5 wt% of aluminum oxide showed better mechanical properties with improved wear resistance. This result clearly indicates that the proposed ceramic materials may be a better alternative for artificial hip material.
Keywords: Artificial hip material _ Ceramic composites _ Mechanical Wear

Hot forming of ultra high strength steel (UHSS) sheet metal grade 22MnB5 boron for channel components using water cooling is studied on a laboratory scale. After hot forming, the different microstructures such as martensite, bainite, and pearlite in formed component are produced, which are closely related with mechanical properties of formed component. The effect of forming start temperature and the contact state between blank and die on the microstructure evolution is investigated. In addition, the effect of processing parameters, such as forming start temperature and blank holder force (BHF), on the final quality of component, i.e., springback, that happens after hot forming of UHSS is investigated. It can be concluded that the forming start temperature has a significant effect on the final mechanical properties of formed components. The effect of forming start temperature on springback is examined in detail under a wide range of operating conditions. The higher the BHF and the forming start temperature, the lower is the springback after hot forming. Furthermore, thermo-mechanically coupled finite element analysis model encompassing heating of sheet blank, forming and quenching are developed for hot forming process. The stress distributions on sheet blank under different conditions during hot forming are compared to gain a fundamental understanding of the mechanism of springback. Comparisons show that numerical simulation results have good agreement with experimental results.

The behaviour of thin composite laminates (unidirectional, cross-ply and angle-ply) under compressive loads has been examined in cases where multiple delaminations are present. The problem is solved using the Finite Element Method (FEM) both with linear analyses, based on the eigenvalues research problem, and with nonlinear analyses, based on incremental-iterative procedures. In particular, the role of the delamination length, of the angle of the plies and of the stacking sequence on the critical load is investigated. Results are compared with those found in literature derived from experimental or numerical 2D analyses.