1,721,017 research outputs found
Magnetic alignment of short carbon fibres in curing composites
Full text linkAlignment of magnetic particles into a viscous fluid by a homogeneous magnetic field has been studied both experimentally and theoretically, but very few studies have investigated the effects of viscosity changes on the capability of achieving complex fibre assemblies in composite materials. In this paper, we study the alignment of short carbon fibres into a viscous matrix whose viscosity is made dependent on the time, in order to simulate the curing process of the composite. A simple model is derived which gives the evolution of fibre position and orientation in terms of the external field and shows good agreement with the experimental evidence on nickel coated carbon fibres embedded in PDMS. The model is used to predict the fibre distribution at curing and hence could be a useful tool to predict the mechanical, electrical and magnetic properties of the composite. A closed form expression of the minimum magnetic field intensity necessary to achieve the desired orientation is derived in terms of the magnetic and geometric properties of the fibres. This equation can be used to guide experiments, and offers a way to discriminate which matrix/fibre configuration can be most proficiently used to have a highly ordered composite
Fabrication and characterisation of short fibre reinforced elastomer composites for bending and twisting magnetic actuation
Full text linkPolydimethylsiloxane (PDMS) films reinforced with short Nickel-coated Carbon Fibres (NiCF) were suc-cessfully fabricated, with the fibres aligned along different directions using an external magnetic field.The fibres were dispersed in the host matrix using sonication and mechanical mixing before being curedfor 48 h in the magnetic field; thanks to the nickel functionalisation, the fibre orientation was achieved bya low intensity field (<0.2 T) which required an inexpensive experimental set-up. The main focus of thisstudy was looking at the actuation potential of this magnetic composite material; successful actuationwas achieved, showing its large displacement capability. The results confirm the presence of an instabilitycontrolled by the magnetic torque, as predicted by the introduced model. The composite films undergo atransition from a bending-only deformed configuration for the 0°fibre specimen, to a twisting-only con-figuration, achieved for fibres at 90°, whereas all the intermediate angles show both bending and twisting.This behaviour mirrors that which is used to propel a selection of marine mammal
Manufacturing & characterization of regenerated cellulose/curcumin based sustainable composites fibers spun from environmentally benign solvents
Full text linkWe report a novel manufacturing method for bio renewable regenerated cellulose fibres modified with curcumin, a molecule is known for its medicinal properties. Ionic liquid namely 1-Ethyl 3-Methyl Imidazolium diethyl phosphate (emim DEP) was found to be capable of dissolving cellulose as well as curcumin. Regenerated cellulose/curcumin composites fibres with curcumin concentration ranging from 1 to 10 wt% were manufactured using dry jet wet fibres spinning process using three different winding speeds. All the cellulose and curcumin composite fibres showed distinct yellow colour imparted by curcumin. The resultant fibres were characterised using scanning electron microscopy (SEM), infrared spectroscopy, mechanical testing, and X-Ray diffraction studies. Scanning electron microscopy of cellulose/curcumin fibres cross-section did not show curcumin aggregates in cellulose fibres indicating uniform dispersion of curcumin in, cellulose matrix. The cellulose chain alignment in cellulose/curcumin composite fibres resulted in tensile strength ranging from 223 to 336 MPa and Young's modulus ranging from 13 to 14.9 GPa. The mechanical properties of cellulose/curcumin composite fibres thus obtained are better than some of the commercially available regenerated cellulose viscose fibres. The wide-angle X-ray diffraction analysis of cellulose/curcumin composite fibres showed good alignment of cellulose chains along the fibre axis. Thus, our findings are a major step in manufacturing strong cellulose fibres with a pharmacologically potent drug curcumin which in future could be used for medicinal, cosmetic and food packaging applications
Sustainable/recyclable composites for heavy-duty vehicle floorings
No full textMills, Andrew - Associate SupervisorComposites are being increasingly used in the automotive industry to fabricate primary and secondary structural components such as tie rods, bumpers and door panels. To comply with the environmental regulations, the automotive sector is adopting sustainable composite materials and manufacturing techniques such as thermoplastic compression moulding. The switch from thermoset to thermoplastic composites to manufacture recyclable components that do not compromise performance is an examplar.
As a part of this M.Sc by Research project, a critical review of components used in buses and trucks is undertaken to find a suitable component to be replaced with sustainable materials. Components like leaf springs and trailer floorings are studied to understand how significant weight reduction can be achieved using alternative materials. Recyclable and low-cost materials such as polypropylene-based composites are considered for weight reduction and improved sustainability/recyclability.
The replacement of hardwood flooring in heavy-duty vehicles with relatively lighter thermoset sandwich panels is observed in the literature as an attempt to reduce weight. However, a research gap is observed in addressing the recyclability of thermoset panels which form cross-links upon curing. This thesis aims to bridge this gap by providing a lightweight alternative to wooden bus floorings while considering its cost and recyclability. Polypropylene and glass fibre-based thermoplastic sandwich panels are developed and reviewed as an alternative. These panels are manufactured using polypropylene glass fibre skins, polypropylene honeycomb and co-bonded using a thermoplastic-based hotmelt glue.
The manufactured panels are found to be 1.4 kg/M²lighter than commercially available birch wood. This decrease in density equates to 51 kg of weight savings when used as a floor in a coach and potential 157 kg weight savings if the panels are used to replace the side panels. Replacing wooden floor panels with thermoplastic alternatives translates to about 1225 litres of lifetime fuel savings and a reduction of 3.4 tonnes in CO₂ emissions for a city bus with more halts.
A three-point bend test is carried out to evaluate the structural performance of the fabricated sandwich panels. The bending test reveals that the manufactured thermoplastic panels show 22 MPa of bending strength. In contrast, the wooden and thermoset counterparts show a bending strength of 34 MPa and 20 MPa, respectively. Low-velocity impact tests are conducted to simulate scenarios like tool drops or hail and debris hitting the floorings. This test at 6 J of impact energy reveals significantly less residual damage when compared to thermoset counterparts.MSc by Research in Manufacturin
Sustainable sandwich composites for automotive applications
Full text linkMills, Andrew - Associate SupervisorThe increasing regulation and demand are raising the pressure on
manufacturing automotive components towards lighter weight and more
recyclability. The commercial road transport industry, contributing a giant part of
emissions, is still significantly utilising wood panels as trucks’/ lorries’/ vans’/
buses’ floor or side walls (of boxes), which is cost-effective and used for a very
long time. However, with the increasing pressure on lighter weight and more
recyclability, the wood panels that could cause deforestation, become a bio-
degradable landfill at the end of life and have a relatively high density are no
longer the best-fit choice for the floor or side panels of such vehicles. The
challenge is to have a floor panel design that could satisfy the increasing
pressure and product requirements such as mechanical properties, price, and
durability.
This research aimed to complete such a challenge by designing sandwich
composite structures with fibre-reinforced plastics and foam materials (foam is
used in case thermal resistance is needed, and honeycomb materials could be
applied when thermal insulating is unnecessary). A fully recyclable sandwich
composite achieved using recycled carbon fibre, polypropylene, and recycled
PET foam underwent various tests to evaluate its applicability as a commercial
transport vehicle floor or side panel. Single fibre tensile tests were operated to
understand the behaviour of the RCF mats. Composite mechanical properties
were estimated from tensile and three-point bending results, and impact
behaviour was analysed after drop tower impact testing. Fibre embedding and
sandwich bonding were verified under SEM, and the resulting sandwich
composite product properties were also tested using three-point bending.
The novelty of such sandwich composite is using RCF with PP to achieve a fully
recycled composite skin, while RCF were used mainly with thermoset resin (in
the same ways as virgin carbon fibre fabrics). Also, thermoplastic materials
such as PP were hard to process with fibre fabrics to form suitable composites
due to their non-polar constitution and high viscosity. Fibre fabric would be
squeezed together and create a layered structure with fibre rich zone at a very
high fibre volume fraction, while the intermedia zone mostly has resins.
However, when RCF and PP are mixed, the randomly oriented fibre could also
hinder the load from the viscose melt and reduce the amount of fabric pressed
closely, forcing some of the melt to pass through inter-fibre areas to create a
better filling. Different forms of PP (sheet, powder) were used, and their effect
on the compression moulding process and the final product were studied in this
research. A faster-pressing cycle was achieved, and a lower pressing pressure
was needed for the powder PP process, but disadvantages came from the
emission and cost side.PhD in Manufacturin
Effect of carbon nanotubes and montmorillonite on the flammability of epoxy nanocomposites
No full textShear-induced anisotropy of concentrated multiwalled carbon nanotube suspensions using x-ray scattering
No full textX-ray scattering is used to measure particle orientation in concentrated multiwalled carbon nanotube (MWNT) suspensions under shear flow. MWNTs were dispersed in a Newtonian suspending fluid (uncured epoxy). The dispersions exhibit shear thinning, approaching the matrix viscosity at high shear rates. This is accompanied by progressive development of MWNT orientation along the flow direction with increasing shear rate. The impact of MWNT aspect ratio and concentration on steady-state orientation is explored. In one sample (2 wt. % dispersion of short MWNTs), orientation was measured in both the flow-gradient (1-2) and flow-vorticity (1-3) planes of shear flow to provide a more complete picture of the three-dimensional orientation state. Also in this sample, 1-3 plane measurements were conducted using both small- and wide-angle x-ray scattering (SAXS and WAXS). While the two methods produce qualitatively similar results, WAXS-derived measures of flow-induced anisotropy are consistently larger than SAXS data. In transient measurements following step-down in shear rate, MWNT orientation is found to decrease on similar time scales as viscosity increases. Prolonged growth of storage modulus is observed following flow cessation, accompanied by an unexpectedly rapid partial loss of MWNT orientation. The rheological and orientation data are discussed in terms of distortion, breakdown, and reformation of percolated MWNT networks in these sample
Injection Pultrusion Simulation for Polyester/Glass Mat/Roving/Mat composites
No full textPolymers & Polymer Composites 13 (6)
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