The development of a numerical modelling approach for carbon bre reinforced plastic energy absorbing structures designed for crash events using Abaqus/CZone is described within this master thesis. Several crash tube series have been designed, manufactured, and tested with a rather unconventional cross-sectional geometry. The squared cross-sectional geometry consisted of "curved" at sections, and double flanges for adhering two halves together. The crash tube halves contain carbon bre epoxy UD laminates, and are manufactured using a hot-press machine. Adjustments for experimental tests were made in the geometry, laminate denition, and impact velocity. Numerical simulations were focused on geometry, laminate definition, impact velocity, flange geometry, material model, laminate thickness, and crush properties. The numerical model consisted of two parts, namely a 3D discrete rigid planar shell as impactor plate without material properties, and a 3D shell crash tube with an imported geometry from Dassault Systems CATIA V5. Material, and cohesive properties were assigned to the crash tube using the Abaqus Ply Fabric material model, and CZone. Mesh seed length was smaller than the critical mesh seed length. An initial clearance between the impactor and crash tube has been implemented within the assembly. Step size was set to 0.05 s, and dynamic explicit step type was selected. General contact was defined using default settings. A qualitative good agreement between numerical and experimental test results is achieved for V100, V500, V600, and V700 series with c.o.v. values for stroke length of 2.2%, 7.0%, 5.3%, and 4.1%,respectively. V500-V700 series are only tested once, whilst the V100 series has been tested five times. The V200 and V300 series with modified geometries achieved c.o.v. values within a complete different order of magnitude for stroke length, namely 14% for V200 series, and 15% for V300 series. Although only three specimens have been tested for the V200, and V300 series, it is not the main reason for this mismatch. The starting deceleration at the linear increasing segment is much lower than observed in experiments, and causes this major difference. Elevated impact velocities for the V1502, and V1503 series tend to have a positive influence on the numerical results, and ensure a higher initial starting deceleration at the linear increasing segment. Numerical results show that increased taper ratios result in decreased decelerations. A flange geometry study showed that implementing a double flange suppresses debonding, and increases the deceleration, as the geometrical stiffness is increased. Not having a flange results in lower decelerations, and larger stroke lengths, as the geometrical cross-section provides less stiffness. A bonded single flange will be debonded, independent of bonding properties, as even extremely high bonding properties have shown direct debonding under impact load. Stiffer laminates result in higher decelerations and shorter stroke lengths. This statement is tested in three different ways, namely by changing the laminate denitions, laminate thickness's, and the crush properties. Three different material models have been tested. Abaqus Ply Fabric has proven to be easiest in usage, and showing a qualitative good agreement with the experimental results. Abaqus Ply Fabric does over predict the stroke length, whereas Hashin, and Tsai-Wu achieve a more accurate stroke length prediction. However, it is safer to over predict the stroke length. No material model is capable of capturing the initial peek decelerations.

Lightweight design is an essential part of lowering CO2 emission, which is one of the mostimportant challenges that the automotive industry is facing today. Carbon fiber reinforcedplastics offer an enormous potential for replacing heavier structural materials like steel andaluminum, however due to their high cost and scarcity, carbon fibers are not a very feasibleoption to use in high volume production applications. It is thought that the introduction of arenewable, low-cost raw material, like lignin, as the carbon fiber precursor would not onlylower the cost but also increase supply compared to its PAN based counterparts. Properties ofthe fiber/matrix interface play a crucial role in governing the overall performance of thecomposite material. Good adhesion between the fiber and the matrix must be ensured in orderto maximize performance. In this study, plasma treatment of softwood lignin based carbonfibers was performed in order to increase the interfacial adhesion between the fiber and thematrix by incorporating functional groups onto the fiber surface. Plasma treatment time,plasma power, chamber pressure and plasma gas type were varied in order to investigate theireffects on the functionalization of the surface by various visual, chemical and mechanicalcharacterization methods. Observations with optical and scanning electron microscopiesshowed the cleaning effects of plasma treatment on the fiber surface by removal of flakes andsmoothing of the fiber surface. The smoothing effect of plasma treatment was later supportedby the subtle increase in the tensile strength of the plasma treated fibers and this wasattributed to the elimination of crack initiators on the surface by a so-called “polishing” effect.Contact angle measurements of the lignin based fibers showed that all plasma gases achieve acertain level of decrease in the contact angle values thus lowering the surface tension. X-rayphotoelectron spectroscopy (XPS) results were analyzed using a design of experimentssoftware with a PLS fit. For the highest amount of surface functionality to be achieved, it wasconcluded that oxygen plasma should be used with high plasma power, low pressure and ahigh treatment time. Detection of Na and S elements combined with unusually lowmechanical properties for all lignin based carbon fibers indicated insufficient carbonization ormolecular orientation for the softwood lignin based carbon fibers used in this study. / GreenLight

Bio-basedcomposites are being increasingly used in applications where weight saving,and environmental friendliness is as important as structural performance. Obviously, bio-based materials have their limitations regarding durability and stability of the properties,but their potential in use for advanced applications can be expanded if they were functionalized and considered beyond their structural performance. Multifunctionalityincomposites can be achieved by modifyingeither of the composite constituents at different levelsso that they can perform energy-associated roles besides their structural reinforcement in the system. For the fibers, this can be done at the microscale by altering theirmicrostructure during spinning process or by applying functional coatings. As for the matrix, it is usually done by incorporating additives that can impart the required characteristics to the matrix. The nano-sized additives that mightbe considered for this objective are graphene and carbon nano-tubes. A big challenge with such materials is the difficulty to reachthe dispersionstate necessary for formation ofstable network to overcome the percolation threshold for conductivity. However, once the network is formed, the composite can have improved mechanical performance together with one or more of the added functionalities such as barrier capabilities,thermal and/or electrical conductivities or electromagnetic interference ability. Enormous work has been done to achieve the functionality incomposites produced with special care in laboratories. However, when it comes to mass production, it is both cost and energy inefficient to use tedious,complex methods for the manufacturing. Hence there is a need to investigate the potential of using scalable and industrial-relevant techniques and materials with acceptable compromise between cost and properties. The work presented in this thesis is performedwithin two projects aiming to achieve functional composites based on natural and man-made cellulosic fibers suitable for industrial upscaling. Conductive Regenerated Cellulose Fibers (RCFs) were produced by coating them with copper by electroless coating process using commercial materials. On the other hand, commercial masterbatches based on Graphene Nano-Platelets (GNPs) were used to produce wood polymer composites (WPC) with added multifunctionality by melt extrusion process. The process is one of the conventional methods used inpolymerproductionand needsno modifications for processingfunctional composites. Both materials together can be used to produce hybrid functional composites. The incorporation of the GNP into HDPE has resulted in improvement in the mechanical propertiesof polymer as well as composite reinforced with wood fibers. Stiffness has increased to a large extent while effect on the strength was less pronounced(>100% and 18% for stiffness and strength at 15%GNP loading). The enhancement of thermal conductivityat higher graphene loadingswas also observed. Moreover, time-dependent response of the polymer has also been affected and the addition of GNP has resulted in reduced viscoplastic strains and improved creep behavior. The copper-coated cellulose fibers showed a significant increasein electrical conductivity(<1Ω/50mm of coated samples) and a potential in use as sensor materials. However, these results come with the cost of reduction in mechanical properties of fibers (10% and 70% for tensile stiffness and strength, respectively) due to theeffect ofchemicals involved in the process.

Graphene nanoplatelets (GNPs) were used to reinforce wood polymer composites (WPCs) in order to achieve multifunctionality. Multifunctionality could be achieved through the GNPs because of their excellent mechanical and electrical properties. The research consists of two parts: HDPE/GNP/WF composites and LLDPE/GNP composites. The HDPE part is a continuation of previous work. Here further mechanical characterisation was done (impact testing), impurities in the composites were identified, the manufacturing process that results in damaged wood particles was investigated and the Young's modulus of the composites were modeled. The impact strength was improved due to the addition of GNPs. WF composites exhibited more brittle behaviour and therefore a lower impact strength. The impurities were identified as some form of nanoclay introduced during the extrusion process. The particles were damaged during the extrusion processes. Little can be done about this as different shear configurations and/or screw speeds will result in a poor GNP dispersion and distribution. Modeling of the Young's modulus was the most accurate through applying the laminate analogy and rule of thumbs. The rule of mixtures does not represent the composites which have a preferred orientation. During the previous work done, it was found that the HDPE composite were not electrically conductive and therefore not multifunctional. The work was therefore continued with LLDPE and GNPs. LLDPE has more branches and is less dense, resulting in potential opportunities for the GNPs to form a network through the polymer. This could lead to a better conductivity. Mechanical and electrical characterisation was done of the LLDPE/GNP composites. Here multifunctionality could also not be achieved as the composites were highly electrically resistant. Mechanical testing indicated that the GNPs significantly enhance the LLDPE matrix. Here an increase of up to 170% could be seen in tensile modulus and an increase of 46% in tensile strength. Furthermore the GNPs improved the flexural properties and increase the resistance to viscoplastic deformation during residual strain testing. Overall the GNPs improve the mechanical properties significantly, but at 10wt.% GNP contents, multifunctionality could still not be achieved.

Aluminium is one of the metals playing a prominent role in automobile industry after cast iron. Because of its light weight property and good mechanical properties. When aluminium reinforced with silicon carbide showing good tribological properties and improved strength. Aluminium silicon carbide needs some good wear and frictional properties to use it as break disc. Aluminium reinforced with 15% and 20% silicon carbide and casted in two different ways, liquid casting and stir casting. Four different composites are compared in this paper. Hardness test was carried out on the samples. Increase in the Vickers hardness with increase in silicon carbide reinforcement for both the castings is observed. Rockwell C hardness is showing decreasing trend with increase in SiC reinforcement. The scratch resistance of the surface under micro level was analysed with the help of nano scratch test. The SiC particles in the aluminium matrix are resisting the indenter from deep deformation of the surface. Frictional forces are dropped whenever the indenter met the SiC particles. In other cases, SiC particles are deforming the aluminium matrix in the form of broken particles. The plastic deformation of aluminium is observed, and material is piled up on sideways of groove at high load.Sliding wear behaviour of the composites are investigated by means of reciprocating pin on plate wear rig. The test was carried out at load of 20N for five different sliding duration. Aluminium with 20% silicon carbide of liquid casting is used as a base metal. The worn-out surface of the samples is analysed in SEM. The metallography of the worn-out samples is showing some deep grooves and abrasion of the material. Wear debris from both the surfaces are forming into a cluster of layers. These layers are protecting the surface from wear in some areas were observed. Composition of tribo layer formed during the test was investigated with the help of EDS analysis. The tribo layer are rich in aluminium and silicon elements because both the samples are made of aluminium silicon carbide.

Total joint arthroplasty surgeries are known to have a high success rate but the longevity of the implants still acts as a limiting factor. Ultrahigh molecular weight polyethylene is the material of choice for the implant bearing surfaces due to its excellent clinical and tribological performance. A common problem associated with the polymer is however the loosening of the implant from its surrounding bone tissue. This phenomenon is caused by a biological reaction to released wear particles. Reducing the release of wear particles will increase the lifespan of implants and can be accomplished by increasing the wear resistance of the material. Crosslinking of the polymer by means of gamma irradiation is a well known approach to achieve an increased wear resistance but eventually leads to oxidation of the polymer. The addition of vitamin E as antioxidant is known to reduce this without significant loss of mechanical properties. A second approach is based on adding reinforcements to the polymer in order to enhance its tribological performance. This work focuses on the thermal and mechanical characterisation of newly developed UHMWPE nano-composites with a focus on the addition of vitamin E and crosslinking by gamma irradiation. Based on previously published results indicating an increased fracture toughness for different composites, Nanodiamonds, multiwalled carbon nanotubes and graphene oxide nanoparticles were dispersed throughout the matrix and consolidated. The thermal characterisation was performed using differential scanning calorimetry, making it possible to identify the different thermal transitions and degree of crystallinity of the polymer. The fracture toughness, an important property in wear due to fatigue, was furthermore characterised by performing three point bending experiments.Finally, by means of a multiaxial pin-on-plate set-up the wear resistance of the materials was analysed.

The emissions of nitrogen oxides (NOx) are a serious environmental problem due to its relationship with the formation of smog, acid rain and because they are dangerous for human and animal health. These gases are produced in high quantities in diesel engines used for automotive applications, and different strategies are being used to reduce them, among which are the Selective Catalytic Reduction (SCR) systems. For its operation, it is necessary a supply of ammonia as NOx reducing agent, but the inefficiency at low temperatures of the systems used nowadays has led to the conception of the solid ammonia storage units (ASS). Unfortunately, the materials currently used, i.e. metal halides, do not meet the ammonia supply requirements at low temperatures and have problems of swelling and agglomeration. In order to find a material with better properties for its application as an ammonia sorbent material, MgCl2 composites with different carbon materials (graphite, graphene, and SWCNTs) were prepared by direct mixing and wet impregnation methods, and characterized in this work. Despite the decrease of total storage capacity, improvements were found in thermal stability and mass retention, as well as in sorption and desorption kinetics, making these materials a first result towards the improvement of the solid ammonia storage units.

Cemented carbide containing sub carbide phases, M6C and M12C, known as eta-phase, increases the lifetime milling cutters due to increased resistance to comb cracks. When milling, the inserts much sustain high temperatures, meaning edgeline toughness and thermal fatigue resistance are needed. To obtain this, finer grains and higher binder content are needed. In this study, WC-Co cemented carbides with eta-phase and Cr as well as a higher binder content are investigated. The microstructure is the focus, with parameters such as eta-phase particle size and volume fraction, WC grain size being evaluated. Another part of the study is the investigate the effect of Cr on heat treatment. The addition of Cr in a WC-Co cemented carbide with eta-phase has shown to give rise to smaller eta-phase particle sizes and WC grain size as compared to without Cr. Also, increasing the volume fraction of eta-phase has less influence on WC and eta-phase particle size. Heat treated samples without Cr is shown to increase the coercivity of the samples at 700 degrees Celsius, without change in WC grain size. The effect is also leading to an increase in hardness. But with addition of Cr, the effect seems to diminish.

In this work four fiber-reinforced polymers and one polymer were tested with four different mechanical testing methods, namely; vickers harness test, scratch test, fatigue test and tensile stress. The testing methods were evaluated according to their applicability on the materials mentioned. The purpose of the work is to give the reader an insight of what mechanical properties of materials mean and what kinds of properties one can expect from fiber-reinforced polymers. The purpose is also to give the reader a good sense of what can be expected from the methods tested on fiber-reinforced polymers. Vickers harness test was found to be a valid method as long as the surface of the material was neither uneven nor processed. Scratch test was found to be an overall good method but was recommended to be used in combination with scanning electron microscope, or other imaging tool for strong magnification. Processing of surfaces proved to affect the results. Tensile test was proved to give the user a good perception of the properties of the material, as long as the material not was woven. Woven materials found to differ a lot from each other. One conclusion from this result is that woven materials are best to be tested several times. Fatigue test was found to require more preparatory time and calculations to be able to give the user any useful results, the loads used in the project was found to be too light weight. Processed surfaces were found to be hard to examine in a scanning electron microscope.

This work has been performed at the Applied Materials ScienceDivision at The Ångström Laboratory in collaboration with SandvikMining AB. The project is part of the joint research programmeCoFree.In this work, the problem of finding an impact test method forcemented carbide rock drill inserts is considered. A suitable testmethod is required to benchmark alternative binder cemented carbidesagainst today’s cobalt based grades. The developed test method isbased on a Charpy pendulum arrangement and utilizes, as in rockdrilling, impact of cylindrical bars to achieve the high impact forcesufficient to fracture the rock drill inserts. The impact issymmetrical with two inserts facing each other, which proves to be anefficient way of damaging the inserts. To gain more informationregarding the force and pulse duration, the history of the impact isrecorded with the use of strain gauges. The measured force curvesfrom repeated tests are typically very similar, a strong indicationthat the test loads the buttons in a well-defined, repeatable way.Also, quasi-static loading of the insert is present in the impactwhich agrees to the results from a static compression test. Thisindicates that the inserts are subjected to quasi-static loading,rather than dynamic loading.A single impact test procedure was developed in this work. Thismethodology proved capable of differentiating the impact performanceof two different button cemented carbide grades. Hence, the test canbe used in the future as a benchmark test. It is however necessary toobtain statistical evidence. The impact performance was measured byobserving cracks produced in the impact contact zone with the aid ofan optical microscope with 85x objective. Radial cracks are veryoften found, often forming a cross around the contact zone. Whenlarge button chippings occur due to the impact loading, a very clearsudden drop in the measured force pulse is seen. This is however notseen for impacts that only produces cracks.