Graphene has the potential to act as a high-performance reinforcement for adhesives or fibre composites when combined with epoxy polymer. However, it is currently mostly available not as single high aspect ratio sheets but as graphene nanoplatelets (GNPs), comprised of stacks of graphene sheets.Graphene nanoplatelets of a range of lateral size, thickness, aspect ratio and surface functionality were used to modify an anhydride cured epoxy polymer.The morphology, mechanical properties and toughening mechanisms of these modified epoxies were investigated. The GNPs were sonicated in tetrahydrofuran (THF) or n-methyl-pyrrolidone (NMP) to facilitate dispersion in the epoxy. The use of THF resulted in large agglomerates, whereas more finely dispersed stacks of GNPs were observed for NMP. The maximum values of modulus (3.6 GPa at 1 wt%) and fracture energy (343 J/m 2 at 2 wt%) were * Corresponding author, Tel.: +44 20 7594 7149Email address: a.c.taylor@imperial.ac.uk (A. C. Taylor) April 11, 2016 measured for the epoxy modified with an intermediate platelet size of approximately 4 µm, compared to 2.9 GPa and 96 J/m 2 respectively for the unmodified epoxy. The Young's modulus was highly dependent on the dispersion quality, whereas the fracture energy was independent of the degree of GNP dispersion. The larger agglomerates of the GNPs which were dispersed in THF toughened the epoxy by crack deflection, whereas the GNPs dispersed in NMP showed platelet debonding, pull-out and plastic void growth of the epoxy. This work indicates that reinforcement and toughening can be achieved at much lower contents than for conventional modifiers. Further, achieving a good dispersion is crucial to the engineering application of these materials, and intermediate-sized graphene achieves the best balance of properties. Preprint submitted to Journal of Materials Science

The microstructure and fracture performance of an anhydride-cured epoxy polymer modified with two poly(styrene)-b-1,4-poly(butadiene)-b-poly(methyl methacrylate) (SBM) block copolymers were investigated in bulk form, and when used as the matrix material in carbon fibre reinforced composites. The 'E21' SBM block copolymer has a higher butadiene content and molecular weight than the 'E41'. A network of aggregated spherical micelles was observed for the E21 SBM modified epoxy, which became increasingly interconnected as the SBM content was increased. A steady increase in the fracture energy was measured with increasing E21 content, from 96 to 511 J/m 2 for 15 wt% of E21. Well-dispersed 'raspberry'-like SBM particles, with a sphere-on-sphere morphology of a poly(styrene) core covered with poly(butadiene) particles, in an epoxy matrix were obtained for loadings up to 7.5 wt% of E41 SBM. This changed to a partially phase-inverted structure at higher E41 contents, accompanied by a significant jump in the measured fracture energy to 1032 J/m 2 at 15 wt% of E41. The glass transition temperatures remained unchanged with the addition of SBM, indicating a complete phase separation. Electron microscopy and cross polarised transmission optical microscopy revealed localised shear band yielding, debonding and void growth as the main toughening mechanisms. Significant improvements in fracture energy were not observed in the fibre composites, indicating poor toughness transfer from the bulk to the composite. The fibre bridging observed for the unmodified epoxy matrix was reduced due to better fibre-matrix adhesion. The size of the crack tip deformation zone in the composites was restricted by the fibres, hence reducing the measured fracture energy compared to the bulk for the toughest matrix materials.

a b s t r a c tA finite volume based implementation of the binary Cahn-Hilliard equation was implemented using an open source library, OpenFOAM. This was used to investigate the development of droplet and co-continuous binary polymer microstructures. It was shown that the initial concentrations of each phase define the final form of the resultant microstructure, either droplet, transition or co-continuous. Furthermore, the mechanical deformation response of the representative microstructures were investigated under both uniaxial and triaxial loading conditions. The elastic response of these microstructures were then compared to a classic representative microstructure based on a face centred cubic arrangement of spheres with similar volume fractions of each phase. It was found that the numerically predicted composite Young's modulus closely followed the upper Hashin-Shtrikman bound for both co-continuous and classical structures, while significant deviations from analytical composite theory were noted for the calculated values of Poisson's ratio. The yield behaviour of the composite microstructures was also found to vary between the co-continuous microstructures and the representative microstructure, with a more gradual onset of plastic deformation noted for the co-continuous structures. The modelling approach presented allows for the future investigation of binary composite systems with tuneable material properties.

To simultaneously address the lower toughness and the build-up of internal heat for fast-curing epoxy matrices, the influence of nominal 100 nm and 300 nm core-shell rubber (CSR) particles on the properties and rheo-kinetics were studied. The fracture energy was enhanced by a factor of 14.5, up to 2572 ± 84 J m−2 with 14.5 wt% of the nominal 300 nm diameter CSR particles, with evidence of cavitation and plastic void growth of the rubber core combined with shear band yielding of the epoxy matrix. These toughening mechanisms were modelled with an approximately linear increase up to 10 wt% for both particle types. At higher concentrations, deviation between the measured and modelled data was observed due to insufficient epoxy to dissipate additional energy. The CSR particles were not filtered out or damaged during the manufacturing of composites and reduced the total heat of reaction with a linear correlation, demonstrating a multi-functionality of simultaneous toughening and reduction of the exothermic peak

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Baked food snacks constitute an important market as a popular consumer product. The mechanical properties of cheese cracker dough at different stages of baking have been investigated as they can relate to the product's texture. The change in mechanical properties during baking was measured whilst the corresponding changes in microstructure were recorded using cryo-SEM at several interrupted baking conditions. The initial modulus of the dough increased with baking time due to starch melting or gelatinisation, melting of fat globules and evaporation of water. Simultaneously gas cells were found to begin forming. The data derived from the uniaxial compression, tension and shear experiments showed that the dough exhibited a rate dependent behaviour at all stages of baking with a power law index of approximately 0.2. Rheometric tests under dynamic heating conditions were also performed and it was found that the modulus decreased significantly, from 150 kPa to 10 kPa, with the initial rise in temperature. This study provides useful data for understanding the evolution of microstructure and rheology during the baking process and its impact on the texture of the final product

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