Effect of fibre treatments on mechanical properties of flax/tannin composites

Due to the inherent environmental benefits of using natural resin (tannin) and natural fibre (flax), flax/tannin composites could be potentially used for vehicle applications. One of the main limitations is the hydrophilic property of flax, resulting in the poor fibre/hydrophobic matrix interface quality. Alkali, acetylation, silane treatment and enzymatic treatment were selected to modify non-woven flax mats to prepare the composites. The fibre morphology was studied through scanning electronic microscopes (SEM). The effects of fibre pre-treatments on dynamic and static mechanical properties of composites were investigated through adequate experiments, such as dynamic mechanical analysis (DMA) and static tensile testing. The modified rougher fibre surface broadened the glass transition peaks of composites due to the improved surface adhesion. However, there is no big improvement of tensile strength after modifications. The pure NaOH (sodium hydroxide) treated composites remain the tensile properties and offer good flax/tannin wettability

Mechanical properties of three-phase polyamide 6 nanocomposites

This work focus on the mechanical properties of three-phase nanocomposites using multiscale reinforcements. The influence of the nano-fillers content, as well as the temperature were studied. Polyamide-6 reinforced with short glass fibre 30 wt.% and with an addition of nanoclay (montmorillonite) and/or nanosilica (SiO2) were tested in order to characterise their tensile properties at room temperature and at 65oC just above the polyamide 6 glass transition temperature. SEM analysis were conducted on the fracture surface of the tensile bars. SEM investigations showed the importance of the interaction matrix/filler for the material behaviour. Our study also shows that the increase of OMMT percentage in polyamide-6/glass fibre composite made the material more brittle and had a negative effect on the tensile properties. Further, for the silica-based nanocomposites, an optimum was found for a nanofillers content of 1wt.%

Nanofiller Fibre-Reinforced Polymer Nanocomposites

In this work, the technology of nano and micro-scale particle reinforcement concerning various polymeric fibre-reinforced systems including polyamides (PA), polyesters, polyurethanes, polypropylenes and high performance/temperature engineering polymers such as polyimide (PI), poly(ether ether ketone) (PEEK), polyarylacetylene (PAA) and poly p-phenylene benzobisoxazole (PBO) is reviewed. When the diameters of polymer fibre materials are shrunk from micrometers to submicrons or nanometers, there appear several unique characteristics such as very large surface area to volume ratio (this ratio for a nanofibre can be as large as 103 times of that of a microfibre), flexibility in surface functionalities and superior mechanical performance (such as stiffness and tensile strength) compared with any other known form of the material. However, nanoparticle reinforcement of fibre reinforced composites has been shown to be a possibility, but much work remains to be performed in order to understand how nanoreinforcement results in dramatic changes in material properties. The understanding of these phenomena will facilitate their extension to the reinforcement of more complicated anisotropic structures and advanced polymeric composite systems

The effect of temperature changes on to quasi-static tensile and flexural performance of glass fibre reinforced PA66 composites

A significant method of reducing CO2 emissions in road vehicles is to reduce the vehicle mass. One means in which this can be achieved is to adopt lightweight materials such as thermoplastic composites. Thermoplastics offer advantages in term of weight when compared to conventional steel and aluminium casting. In this study thermal mechanical testing has been conducted on two types of commercial polyamide 66 (PA66) with 35 wt.% short glass fibre reinforcement. One of the materials was impact modified with an elastomer to increase material toughness. Experimental results showed both the reinforced PA66 materials to be temperature dependent. All test results demonstrated the trade-off in the mechanical properties of the two materials especially the impact modified. PA66 with 35 wt.% short glass fibre exhibits the best tensile strength, flexural strength and modulus for each temperature tested. Whereas the impact modified PA66 with 35 wt.% short glass fibre exhibits the higher strain and toughness for each temperature tested

A review on the effect of mechanical drilling on polymer nanocomposites.

Over the past decade, polymer nanocomposites have undergone intensive research and development ensued by its increasing implementation within commercial applications. Consequently, the full life-cycle performance and any health risks associated with these materials have become of major interest. Throughout its use, a nanocomposite will undergo industrial machining where drilling can lead to material damage and/or exposure to the potentially toxic nanoparticles. This study assesses the existing and perspective research on nanocomposite drilling. Currently, although considerable amount of studies have investigated machining on conventional composite materials, there is a lack in knowledge on the effect of drilling on nanocomposites. The data underlines the various drilling parameters that will affect and influence the damage to the material and nano-sized particles released. Importantly, previous studies have identified potential mechanical damage caused by drilling and the release-ability of toxic nanoparticles from nanocomposites. It is therefore crucial to develop a full understanding and characterization on the effect of drilling on polymer nanocomposites

Shock propagation behaviour and determination of Gruneisen state of equation for pultruded polyester/glass fibre-reinforced composites.

Polyester fibres reinforced with glass fibres hybridised polyester resin composite (PFR/GFHC) is a unconventional complex high-molecular weight crosslinked network polymer composite. This novel composite can be used in the manufacture of structural body parts for lightweight vehicles, armour vest for body protection as well as armours for vehicles. For body armour applications, it is important to determine the dynamic behaviour of PFR/GFHC during high velocity impact. In this work, we propose a method of calculating Gurneisen parameter from the measured Hugoniot in shock velocity – particle velocity of polyester based composites product by high velocity actuated nail gun impact. Several high-velocity impacts were conducted on pultruded plates using a power actuated nail gun with different cartridges and varying nail sizes. The experimentally measured Hugoniot in shock velocity – particle velocity space was determined as Us = 2.872 + 1.22Up (ρ0 = 1.25 g/cc) and low gradient observed for Gruneisen parameter as calculated from measured Hugoniot against V0/V shows higher shock absorption of PFR/GFHC for impact velocity

Thermo-mechanical performance of poly(lactic acid)/flax fibre-reinforced biocomposites.

In this study, the thermo-mechanical performance of flax fibre reinforced poly lactic acid (PLA) biocomposites was investigated for the potential use in load bearing application such as body-in-white and body structures in the automotive sector. Focus was given into the relationships between the thermal and mechanical properties, and the material response under different loading and environmental conditions. The strength (72. MPa) and stiffness (13. GPa) of flax/PLA composites investigated indicate a very promising material to replace traditional choices in load bearing application. The PLA's crystallinity was measured to approximately 27%. Annealing above 100. °C for an hour decreased that value to 30%, but analysis of tensile results of annealed specimens reveals a significant reduction of both the tensile strength and modulus. This reduction is associated with micro-cracking that occurred on the surface of PLA during the heating as well as deterioration of the flax properties due to drying. The study results show that strength and modulus increased with increasing strain rates, while elongation at break reduces respectively. A modulus of 22. GPa was recorded in 4.2. m/s crosshead velocity. Further, flax/PLA showed significantly higher modulus than flax/epoxy for the composites studied. Improvement of the interfacial bonding and the temperature characteristics, combined the thermoplastic nature of PLA, demonstrates that flax/PLA composites is ideal for use in structural automotive applications

An assessment on effect of process parameters on pull force during pultrusion.

This research investigates the process behaviour by prediction of the pull force required to drag raw materials through heated die during pultrusion with different reinforcing material configurations. Pultrusion is a continuous manufacturing process that is widely used for composite profiles. A device was designed to apply friction force by pulling on 'resin-impregnated' fibres, with both liquid resin and partially cured resin. This device was used to measure pulling force in conjunction with temperature and resin conversion. This enabled the experimental simulation of materials tracing for both short and long die lengths. Differential scanning calorimetry (DSC) was used to determine polymer conversion. The results show that the downstream part of a die has no significant effect on the pulling force before a certain degree of conversion is achieved. The research has also shown that higher resin conversion leads to higher friction in the viscous /liquid zone. The difference is much more significant when the temperature is low (e.g. room temperature), reducing when the temperature rises. A mathematical model predicts that increases in compaction pressure will have an impact on increasing fibre volume fraction and drag velocity, which is an opposing characteristic to tapping angle and considerations of part thickness. Similarly, many parameters - like shrinkage, viscous force and dry friction - were modelled and simulated for ortho polyester resins as a function of temperature and resin conversion during dynamic pulling. The study is directly applicable in configuration of pultrusion manufacturing; enabling customisation for a specific configuring material, components manufacturing and respective die design for the profile

The influence of graphene oxide on nanoparticle emissions during drilling of graphene/epoxy carbon-fiber reinforced engineered nanomaterials.

Graphene oxide (GO) nanoparticles are increasingly being used to tailor industrial composites. However, despite the advantages, GO has shown conceivable health risks and toxicity to humans and the environment if released. This study investigates the influence that GO concentrations have on nanoparticle emissions from epoxy-reinforced carbon fiber hybrid composites (EP/CF) during a lifecycle scenario, that is, a drilling process. The mechanical properties are investigated and an automated drilling methodology in which the background noise is eliminated is used for the nanoparticle emissions measurements. Real-time measurements are collected using a condensation particle counter (CPC), a scanning mobility particle sizer spectrometer (SMPS), a real-time fast mobility particle spectrometer (DMS50) and post-test analytical methods. The results observe that all three nanoparticle reinforced samples demonstrated a statistically significant difference of up to a 243% increase in mean peak particle number concentration in comparison to the EP/CF sample. The results offer a novel set of data comparing the nanoparticle release of GO with varying filler weight concentration and correlating it the mechanical influence of the fillers. The results show that the release characteristics and the influence in particle number concentration are primarily dependent on the matrix brittleness and not necessarily the filler weight concentration within the nanocomposite

Cloning and expression of deoxyhypusine synthase from<i> Plasmodium vivax </i>and<i> Theileria parva </i>as an approach for target evaluation in anti-parasitic chemotherapy

An important issue facing global health today is the need for new, effective and affordable drugs against malaria and a veterinary parasitic disease named Theileriosis, particularly in resource-poor countries. The parasite P. vivax which causes benign malaria and T. parva causing East Coast Fever (ECF) or Theileria annulata causing Tropical Theileriosis (MCF) belong to the group of Apicomplexa which have an apicoplast. The apicoplast is a relic of the chloroplast which is necessary for the parasite to invade its host. Genes of the apicoplast have shown to be very important drug targets since they do not exist in their human or animal counterpart. However nuclear encoded genes which show significant differences with respect to the structural domains of their proteins might also be attractive drug targets. Here we report about the cloning and characterization of the deoxyhypusine synthase gene (DHS) from both parasites. DHS catalyzes the first committed step in the biosynthesis of the unique amino acid hypusine in eukaryotic initiation factor 5A (eIF-5A). The enzyme transfers an aminobutyl moiety from the triamine spermidine to a specific lysine residue of the precursor protein. Deoxyhypusinylated eIF-5A is subsequently hydroxylated by deoxyhypusine hydoxylase (DOHH) which completes eIF-5A activation. Surprisingly we identified 4-saturated piperidone monoesters as putative DOHH inhibitors with antiplasmodial activity. Recent results have shown that DHS is a valuable drug target in P. falciparum for the therapy of cerebral malaria. The putative DHS protein from P. vivax displays a FASTA score of 74 relative to that from the human parasite P. falciparum. The ORF encoding 456 amino acids was expressed under control of IPTG-inducible T7 promoter, and expressed as a protein of approximately 50 kDa (theoretically 52.7 kDa) in E. coli BL21 DE3 cells. The N-terminal histidine-tagged protein was purified by Nickel-chelate affinity chromatography under denaturing conditions. DHS has a theoretical pI of 6.0 and its specific enzymatic activity was determined as 1268 U/mg protein The inhibitor, N-guanyl-1, 7-diaminoheptane (GC7), suppressed specific activity by 36-fold. The Theileria parva gene encodes for an ORF of 371 amino acids with a theoretical pI of 5.4 and a calculated molecular weight of 44,8 kDa. Theileria parva dhs has a FASTA score of 49 to its host Bos taurus. Expression of the histidine tagged protein in pET28a in E. coli BL21 DE3 cells failed