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Heterostructured metallic materials have drawn attention because of their superior mechanical properties compared to their homogeneous counterparts. This paper evaluates a novel and easy-to-scale approach for manufacturing gradient materials via localized impact loading and reveals the main strengthening mechanism in a high stacking-fault energy material. Impact loading caused heterogeneous strain distributions and strain hardening gradients from the surface towards the inside of the rods. The yield strength and elongation gradients of the impacted rods were 130 MPa–75 MPa and 10 %–25 %, respectively, over a depth of 0 mm–4 mm. This represents a yield strength increment of over 100 % in comparison to the homogeneous counterpart. The appearance of both microscopic and macroscopic heterostructured deformation zones was corroborated by geometrically necessary dislocation and nanoindentation profiles. In this context, the density of dislocations diminished with increasing distance from the impacted surface, leading to a concentration of dislocations in the grains adjacent to the surface. Near the impacted surface, dislocations piled up around the grain boundaries of adjoining grains, creating micro-plastic gradients that that extended into the grain interiors. The localized impact experiments resulted in a heterostructured pure Al rod with gradient properties. Specifically, 50 % of the rod's thickness achieved strengths that exceeded the as-received condition, while the remaining 50 % maintained elongations that exceeded 15 %., Peer Reviewed, Objectius de Desenvolupament Sostenible::12 - Producció i Consum Responsables, Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura, Postprint (published version)

Adding textures to surfaces is known to improve the external appearance of injection moulded components. However, when high surface quality is required, normally a paint coating is applied on top of the moulded textured surface. In this work, an alternative to painting for obtaining high quality surfaces is proposed, following an environmental-friendly process and having low production cost. Three different surface textures obtained by injection moulding have been characterized and compared with a painted one. Alternative topographical parameters such as the absolute functional height (AFH), the functional height distribution (FHD), texture slope (TS) or texture aperture angle (TAA) besides to the traditional roughness parameters such as the arithmetical mean height (Sa) and the root mean square height (Sq) have been utilized to characterize the random surface textures. The relationships between these parameters and the surface quality appearance represented by gloss and reflectivity contrast have been established using a new total appearance measurement (TAM) apparatus. It was found that by applying secondary operation on the textured mould cavity, such as adding micro roughness features or coatings, equal apparent quality to the ones obtained by painting can be reached., Postprint (author's final draft)

In this research, the influence of the macro- and micro-topography on randomly micro-textured polypropylene surfaces has been studied. An initial characterization of the underlying surface was carried out using three-dimensional (3D) technologies such as chromatic and white light confocal microscopy. A multi-scale analysis methodology was employed for analysing the surface at either macro- or micro-scales. Among others, topographic characteristics such as peak-to-valley symmetry and the amount of micro-asperities were analysed to quantitatively determine the scratch and mar visibility resistance. The results show that surfaces with higher symmetry in their functional height distributions yield lower lightness variation (¿L*) between the scratch pattern and its residual background height (RBH). This allows for a better suitability in hiding the scratch damage. On the other hand, topographies with less amount of micro-asperities on top of the texture provided a better mar resistance. In these cases, deformation mechanisms such as ironing are minimized, resulting in a lower gloss variation and lower contrast between the damaged area and its surroundings., Peer Reviewed, Postprint (author's final draft)

Preprint

Low flammability, foam-like materials based on bio-based, renewable ammonium alginate and sodium montmorillonite clay were fabricated through a simple, environmentally-friendly freeze-drying process in which water is used as solvent. These materials exhibit mechanical properties similar to those of rigid PU foams or balsa; the compressive modulus (1–97 MPa) and density (0.047–0.174 g/cm3) increase with increasing solids content, with an associated change from a layered to network microstructure structure. Calcium ions, either added directly or indirectly via CaCO3/gluconolactone (GDL) are an effective crosslinking agent for alginate, with the GDL route providing the greatest enhancement of mechanical properties. The thermal stability of the aerogels is also enhanced by the presence of crosslinking. The alginate/clay aerogels possess inherently low flammability, as measured by cone calorimetry, with heat release values decreasing as the proportion of clay in the composites is increased., Peer Reviewed, Postprint (published version)

Carbon fibre reinforced cyclic butylene terephthalate (CF-pCBT) composites non-isothermally processed by vacuum infusion starting from a one-component system have been successfully manufactured. Both the micro-structure and low-energy impact properties of the CF-pCBT have been investigated and compared with an epoxy system (CF-epoxy). The CF-pCBT composite presents higher solidification shrinkage than the CF-epoxy one, and its void content doubles that of the CF-epoxy. The CF-epoxy composite’s critical delamination threshold energy is slightly higher than that of the CF-pCBT, whereas the CF-pCBT composite absorbs twice as much energy before being penetrated. The lower interlaminar shear strength of the CF-pCBT composite is suggested to be the origin of its higher energy absorbing capability and less brittle behaviour., Peer Reviewed, Postprint (published version)