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Journal articleGuild F, Kinloch AJ, Masania K, et al., 2018,
The fracture of thermosetting epoxy polymers containing silica nanoparticles
, Strength, Fracture and Complexity, Vol: 11, Pages: 137-148, ISSN: 1567-2069An epoxy resin, cured with an anhydride, has been modified by the addition of silica nanoparticles. The particles were introduced via a sol-gel technique which gave a very well dispersed phase of nanosilica particles, which were about 20 nm in diameter, in the thermosetting epoxy polymer matrix. The glass transition temperature of the epoxy polymer was unchanged by the addition of the anoparticles, but both the modulus and toughness were increased. The fracture energy increased from 77 J/m2 for the unmodified epoxy to 212 J/m2 for the epoxy polymer containing 20 wt.% of nanosilica. The fracture surfaces were inspected using scanning electron and atomic force microscopy, and these microscopy studies showed that the silica nanoparticles (a) initiated localised plastic shear-yield deformation bands in the epoxy polymer matrix and (b) debonded and allowed subsequent plastic void-growth of the epoxy polymer matrix. A theoretical model for these toughening micro mechanisms has been proposed to confirm that these micromechanisms were indeed responsible for the increased toughness that was observed due to the presence of the silica nanoparticles in the epoxy polymer.
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Journal articleGesslbauer S, Cheek H, White A, et al., 2018,
Highly active aluminium catalysts for room temperature ring-opening polymerisation of rac-lactide
, Dalton Transactions, Vol: 31, ISSN: 1477-9226A new series of aluminium complexes bearing ‘catam’ ligands has been synthesised and fully characterised. They were found to exhibit high activity at room temperature for rac-lactide ring-opening polymerisation, a rather rare feature for aluminium-based catalysts.
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Journal articleKinloch AJ, Uhlig C, Bauer J, et al., 2018,
Influence of backbone structure, conversion and phenolic co-curing of cyanate esters on side relaxations, fracture toughness, flammability properties and water uptake and toughening with low molecular weight polyethersulphones
, Reactive and Functional Polymers, Vol: 129, Pages: 2-22, ISSN: 1381-5148The effect of backbone structure and conversion of polycyanurate networks on solid state properties has been studied and compared to co-curing with bisphenol-A. Dynamic mechanical behaviour, density, flammability properties, fracture toughness and long-term water uptake were investigated. The intensity of the γ-relaxation increases, room temperature density decreases with increasing conversion, both due to increasing free volume with increasing conversion. A brittle-ductile transition was detected by precise fracture toughness measurements; above a critical conversion the fracture toughness rises suddenly from extremely low values to a plateau or maximum: Networks with higher toughness show a maximum, those with lower toughness a plateau. Bisphenol-A modification causes intrinsic toughness variations. Toughening of two different cyanate esters with polyethersulphones synthesized with various molecular weights between 3000 and 10,500 (Mn) was investigated. Significant toughening effects can be achieved already with intermediate molecular weights lower than those of commercially-available high-Tg amorphous thermoplastics. Long-term water uptake measurements at 28 °C, 50 °C and 70 °C over two years show a non-Fickian part of the water uptake for all cyanate esters even at temperatures as low as 28 °C. The effects of backbone structure, conversion and storage temperature are discussed in detail.
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Journal articleCarroll D, Constantinou A, Stingelin N, et al., 2018,
Scalable syntheses of well-defined pentadecablock bipolymer and quintopolymer
, Polymer Chemistry, Vol: 9, Pages: 3450-3454, ISSN: 1759-9954The one-pot syntheses of two pentadeca-(15)-block methacrylate-based amphiphilic copolymers, specifically a bipolymer (AB)7A and a quintopolymer (ABCDE)3, are being reported using a fast and easy to scale up procedure that does not require any intermediate purification steps. Both syntheses were carried out using sequential group transfer polymerisation (GTP) and took under 3.5 h. Amino-containing (DMAEMA, DEAEMA), ether (THFMA, MEGMA) and alkyl (EtMA) methacrylates were used to produce the multiblock copolymers with a final Đ < 1.3.
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Book chapterTaylor AC, 2018,
Adhesives with nanoparticles
, Handbook of Adhesion Technology: Second Edition, Pages: 1677-1702, ISBN: 9783319554105The increased commercial availability and the reduced prices of nanoparticles are leading to their incorporation in polymers and structural adhesives. This chapter outlines the principal types of nanoparticles, and the methods that may be used to disperse the particles in a polymer matrix. It discusses how nanoparticles can alter the mechanical properties (e.g., stiffness), electrical properties (e.g., conductivity), functional properties (e.g., permeability, glass transition temperature), and fracture performance of thermoset polymers. The effect of nanoparticles on joint performance is also discussed.
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Journal articleZhang R, Li-Mayer J, Charalambides M, 2018,
Development of an image-based numerical model for predicting the microstructure-property relationship in alumina trihydrate (ATH) filled poly(methyl methacrylate) (PMMA)
, International Journal of Fracture, Vol: 211, Pages: 125-148, ISSN: 0376-9429Particulate composites are found in a wide range of applications. Their heterogeneous microstructure affects their bulk behavior and structural performance, however tools for predicting this important structure-property relationship are still lacking. In this study, a numerical method that can provide predictions of the mechanical response of a particulate polymeric matrix composite as a function of volume fraction and particle mean diameter is presented. The work is derived for an alumina trihydrate filled poly(methyl methacrylate) but the methodology is generic and can be used for any particulate composite. Representative Volume elements are determined through images obtained from scanning electron microscopy. The model takes into account the possibility of failure through interface debonding as well as cracks through the matrix. The model predictions for the modulus and fracture strength of the composites are validated through independent experiments on the composite. The numerical results are also used to qualitatively explain the trends measured regarding the fracture toughness of the composites. Compared to other literature on particulate composites, our study is the first to report accurate stress–strain distributions as well as fracture predictions whilst all the necessary model parameters defining the failure criteria are all derived through independent experiments. This paves the way for a relatively simple methodology for determining structure-property relationships in composites design, enabling smarter material utilization and optimal mechanical properties.
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Journal articleVespa E, Nikolov N, Grimm M, et al., 2018,
Efficient octree-based volumetric SLAM supporting signed-distance and occupancy mapping
, IEEE Robotics and Automation Letters, Vol: 3, Pages: 1144-1151, ISSN: 2377-3766We present a dense volumetric simultaneous localisation and mapping (SLAM) framework that uses an octree representation for efficient fusion and rendering of either a truncated signed distance field (TSDF) or an occupancy map. The primary aim of this letter is to use one single representation of the environment that can be used not only for robot pose tracking and high-resolution mapping, but seamlessly for planning. We show that our highly efficient octree representation of space fits SLAM and planning purposes in a real-time control loop. In a comprehensive evaluation, we demonstrate dense SLAM accuracy and runtime performance on-par with flat hashing approaches when using TSDF-based maps, and considerable speed-ups when using occupancy mapping compared to standard occupancy maps frameworks. Our SLAM system can run at 10-40 Hz on a modern quadcore CPU, without the need for massive parallelization on a GPU. We, furthermore, demonstrate a probabilistic occupancy mapping as an alternative to TSDF mapping in dense SLAM and show its direct applicability to online motion planning, using the example of informed rapidly-exploring random trees (RRT*).
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Conference paperCzarnowski J, Leutenegger S, Davison AJ, 2018,
Semantic Texture for Robust Dense Tracking
, 16th IEEE International Conference on Computer Vision (ICCV), Publisher: IEEE, Pages: 851-859, ISSN: 2473-9936 -
Journal articlevan Sebille E, Griffies SM, Abernathey R, et al., 2017,
Lagrangian ocean analysis: fundamentals and practices
, Ocean Modelling, Vol: 121, Pages: 49-75, ISSN: 1463-5003Lagrangian analysis is a powerful way to analyse the output of ocean circulation models and other ocean velocity data such as from altimetry. In the Lagrangian approach, large sets of virtual particles are integrated within the three-dimensional, time-evolving velocity fields. Over several decades, a variety of tools and methods for this purpose have emerged. Here, we review the state of the art in the field of Lagrangian analysis of ocean velocity data, starting from a fundamental kinematic framework and with a focus on large-scale open ocean applications. Beyond the use of explicit velocity fields, we consider the influence of unresolved physics and dynamics on particle trajectories. We comprehensively list and discuss the tools currently available for tracking virtual particles. We then showcase some of the innovative applications of trajectory data, and conclude with some open questions and an outlook. The overall goal of this review paper is to reconcile some of the different techniques and methods in Lagrangian ocean analysis, while recognising the rich diversity of codes that have and continue to emerge, and the challenges of the coming age of petascale computing.
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Journal articleSaunders MI, Bode M, Atkinson S, et al., 2017,
Simple rules can guide whether land- or ocean-based conservation will best benefit marine ecosystems
, PLoS Biology, Vol: 15, ISSN: 1544-9173Coastal marine ecosystems can be managed by actions undertaken both on the land and in the ocean. Quantifying and comparing the costs and benefits of actions in both realms is therefore necessary for efficient management. Here, we quantify the link between terrestrial sediment runoff and a downstream coastal marine ecosystem and contrast the cost-effectiveness of marine- and land-based conservation actions. We use a dynamic land- and sea-scape model to determine whether limited funds should be directed to 1 of 4 alternative conservation actions—protection on land, protection in the ocean, restoration on land, or restoration in the ocean—to maximise the extent of light-dependent marine benthic habitats across decadal timescales. We apply the model to a case study for a seagrass meadow in Australia. We find that marine restoration is the most cost-effective action over decadal timescales in this system, based on a conservative estimate of the rate at which seagrass can expand into a new habitat. The optimal decision will vary in different social–ecological contexts, but some basic information can guide optimal investments to counteract land- and ocean-based stressors: (1) marine restoration should be prioritised if the rates of marine ecosystem decline and expansion are similar and low; (2) marine protection should take precedence if the rate of marine ecosystem decline is high or if the adjacent catchment is relatively intact and has a low rate of vegetation decline; (3) land-based actions are optimal when the ratio of marine ecosystem expansion to decline is greater than 1:1.4, with terrestrial restoration typically the most cost-effective action; and (4) land protection should be prioritised if the catchment is relatively intact but the rate of vegetation decline is high. These rules of thumb illustrate how cost-effective conservation outcomes for connected land–ocean systems can proceed without complex modelling.
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