Epoxy powders were investigated as a processing route for fast, low-cost manufacturing of thicksection fibre reinforced polymer parts. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and parallel-plate rheometry were used to characterise the material for realistic processing conditions. The epoxy powders contained heat-activated curing agents and exhibited good thermal stability at and above typical processing temperatures (160-180°C). The exothermic heat produced during curing was found to be small when compared to some conventional epoxies. Similarly, it was shown that epoxy powders can be melted between 45 and 120°C to achieve low viscosities for fibre tow impregnation, without inducing significant cure. Semi-empirical cure kinetics and chemorheological models were presented, which can be used to predict the epoxy's behaviour during part consolidation and curing. Modifications were made to an existing cure kinetics model to better represent the behaviour of the epoxy at lower temperatures. The relationship between glass transition temperature and the degree-of-cure was described using the DiBenedetto equation and was implemented in an existing chemorheological model. The chemorheological model was applied to a standard process cycle to assess the accuracy of the model and the effectiveness of the process cycle.

Thick-section composite parts are difficult to manufacture using thermosetting resins due to their exothermic curing reaction. If processing is not carefully controlled, the build-up of heat can lead to warpage or material degradation. This risk can be reduced or removed with the use of a low-exotherm resin system. Material and process models are presented which describe vacuum-bag-only processing of thick-section composites using a novel, low-exotherm epoxy powder. One-dimensional resin flow and heat transfer models are presented which govern the fabric impregnation and temperature evolution, respectively. A semi-empirical equation is presented which describes the sintering of the epoxy powder. The models are coupled via laminate thickness change, which is determined for a simplified ply microstructure. The resulting system of equations are discretised and solved numerically using a finite difference code. A case study is performed on a 100-ply laminate, and the advantages and disadvantages of using epoxy powders are discussed.

Validations of a one-dimensional process model are carried out by manufacturing thick-section glass-fibre reinforced composite laminates with a low-exotherm epoxy powder. An experimental apparatus is developed which heats the laminates from one side while insulating the remaining sides (i.e. approximating one-dimensional heat transfer conditions).Temperatures within the laminate are measured using thermocouples and a linear variable differential transformer is used to measure the thickness change of the laminate, with respect to time, due to powder sintering and fabric impregnation. The experimental results are analysed and used to validate process models for the epoxy powder system. Process simulations are performed to analyse the influence of material format, laminate thickness change, and heating methods (i.e. one-sided heating vs two-sided heating, and heated tooling vs oven heating). It is shown that epoxy powder eliminates the risk of 'thermal runaway', but thermal and cure gradients persist for a conventional processing cycle. Methods to inhibit the evolution of these gradients are explored using process simulations. These methods include modifying the temperature cycle and using multiple epoxy powders with varied latent curing properties.

Highlights:-The powder-epoxy towpregging process was described in detail for both carbon fibres and basalt fibres.-Excellent static mechanical properties were reported for unidirectional carbon-fibre/powder-epoxy composites and the influence of fibre volume fraction (FVF) was analysed.-Two types of basalt fibre were tested, showing comparable mechanical properties to glass fibre composites.-A hygrothermal study of both carbon-fibre composites and basalt-fibre composites showed that the latter had a greater sensitivity to water uptake and immersed ageing.

Big-Tech's data centres have recently emerged as important socio-political figures in the ongoing digitalization of the Danish state. Locating vast swathes of data in a country renowned for its renewable energy supply begs the question as to the nature of the relationship between the two. Our ethnographic interest resides in analysing how Denmark is rapidly becoming an attractive European location for US data centres, and in exploring the transformative processes through which the state is being reconfigured as digital. In doing so, we emphasise the role of infrastructures in digital statemaking and draw upon a particular reading of anthropological exchange theory to conceptualize how the state is being reconstituted through exchange practices with data centre actors. We argue that as Big-Tech territorialises state land and resources, the state in turn reterritorializes the promising digital futures that come with Big-Tech, making visible its new digital frontier.