Elsevier Vernet, N.; Ruiz, E.; Advani, S.; Alms, JB.; Aubert, M.; Barburski, M.; Barari, B.... (2014) Abstract:In this second international permeability benchmark, the in-plane permeability values of a carbon fabric were determined by 12 participants worldwide. One other participant also investigated the deformation of this fabric. The aim of this work was to obtain comparable results in order to make a step towards standardization of permeability measurements of fibrous reinforcements. The procedures used by most participants were according to the guidelines defined for this exercise after the first benchmark. Unidirectional injections in three in-plane directions of the fabric were conducted to determine the unsaturated in-plane permeability tensor. Parameters such as fiber volume fraction, injection pressure and fluid viscosity have been fixed in order to minimize sources of scatter. The comparison of the results from each participant was encouraging. The scatter between data obtained while respecting the test guidelines was close to the scatter of the setups themselves. A slightly 2 higher dispersion was observed when some parameters differed from the recommendations.Overall, a good correlation is observed between all the results of this exercise.

Metals are known to exhibit mechanical behaviour at the nanoscale different to bulk samples. This transition typically initiates at the micrometre scale, yet existing techniques to produce micrometre-sized samples often introduce artefacts that can influence deformation mechanisms. Here, we demonstrate the casting of micrometre-scale aluminium single-crystal wires by infiltration of a salt mould. Samples have millimetre lengths, smooth surfaces, a range of crystallographic orientations, and a diameter D as small as 6 μm. The wires deform in bursts, at a stress that increases with decreasing D. Bursts greater than 200 nm account for roughly 50% of wire deformation and have exponentially distributed intensities. Dislocation dynamics simulations show that single-arm sources that produce large displacement bursts halted by stochastic cross-slip and lock formation explain microcast wire behaviour. This microcasting technique may be extended to several other metals or alloys and offers the possibility of exploring mechanical behaviour spanning the micrometre scale.

Single-crystalline cast aluminium microwires with a diameter near 15 mm are characterised by Laue microdiffraction. A microwire in the as-cast condition exhibits a misorientation below 1 • over a length of 500 mm. The measured density of geometrically necessary dislocations is low, ,10 12 m −2 , though local maxima up to one order of magnitude higher are found. After tensile deformation to failure, the dislocation density is significantly increased in microwires that have mostly deformed in single slip (≈2 × 10 13 m −2), and yet higher when deformation has occurred by multiple slip (≈6 × 10 13 m −2). In deformed single slip oriented microwires, the streaking directions of Laue spots show that dislocations are stored (though not exclusively) on the primary slip system. Results are consistent with a deformation mechanism governed by rotating, likely singlearm, sources.

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This data article presents a methodology and the corresponding code developed to perform and process stress relaxation tests where samples display superimposed (i) classical, continuous logarithmic relaxation together with (ii) sudden displacements manifest as abrupt stress decreases. The method extracts the activation area characteristic of the thermally activated mechanism that drives continuous plastic deformation in the material. We report stress relaxation data appertaining to as-cast (27) and annealed (2) aluminium microwires produced through a microcasting process. For an interpretation and discussion of the data on annealed microwires the reader is referred to “ The effect of size on the plastic deformation of annealed cast aluminium microwires” (Verheyden et al., In Press) [1]. For full descriptions of the production process of aluminium microwires or of the tensile testing equipment and procedure the reader is referred to Krebs et al. (2017) [2].