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[Display omitted] • Heat sinks based on standard and novel, non-standard morphologies were designed using parametric modelling and computational optimization. • To allow their cross-morphological performance comparison, equity was established between them with regard to (thermal) mass. • The heat sinks were compared in a passive cooling application using numerical simulation and experimental methods. • Some heat sink morphologies performed more efficiently than others in the passive cooling application. • The approach to cross-morphological performance comparison is shown to be viable, despite shortcomings in technologies used. Cross-morphological performance comparisons in mechanical engineering design may well resemble comparisons of apples and oranges. They are meaningful only if pertinent properties shared across compared morphologies (so-called tertia comparationis) are identified, and equity with regard to these properties is established. This article demonstrates such an approach with the use of parametric geometry modeling, optimization, and additive manufacturing, enabling a thermal performance comparison of different heat sink morphologies, using both steady-state numerical simulation and experimental evaluation, by establishing equity across the compared heat sinks in terms of (thermal) mass. Limitations in additive manufacturing precision, as well as inconsistencies between numerical simulation and experimental evaluation results, were encountered in this case study. Likely resulting from the heat sinks' thermal properties on the additive manufacturing process and the simulation environment's disproportionate reliance on convection surface area, these limitations and inconsistencies will likely diminish as additive manufacturing and numerical simulation technologies improve. The cross-morphological comparison approach presented here is shown to be viable in principle and may inform decision-making in applied mechanical engineering design research and practice. [ABSTRACT FROM AUTHOR]

Abstract Structures with negative Poisson's ratios have been widely applied in existing engineering, especially in the field of energy absorption. To design double-arrowed auxetic structures to better absorb energy, it is essential to conduct parametric analysis on their crashworthiness. In this paper, the effect of the geometric parameters on the crashworthiness performance is analyzed thoroughly on both macro- and micro-sized scales. At the macro scale, the effect of the slenderness ratio and size of the unit cell are analyzed. Additionally, the critical slenderness ratio is derived to distinguish the deformation modes under axial impact loading. At the micro scale, analysis of the effect of the angles and thickness of beams on the crashworthiness performance is conducted. It is found that the crashworthiness performance of double-arrowed auxetic structure is more sensitive to the parameters of the long-inclined beam than those of the short one. The discussion in this paper can help engineers to better design and optimize the double-arrowed crash box. Graphical abstract Unlabelled Image Highlights • The parametric analysis of the crashworthiness of double arrowed structure is conducted. • The critical slenderness ratio is derived to distinguish different deformation modes. • The crashworthiness is more sensitive to the angle and thickness of long inclined beams. [ABSTRACT FROM AUTHOR]

[Display omitted] • The trabecular form-function relationship was condensed into 2 equations, linking volume fraction and Fabric Tensor to local stress. • A bio-inspired porous pattern was proposed to reproduce the trabecular form-function relationship by adapting its geometry to stress. • A mass reduction method was established in which a mechanical part architecture is locally adapted to the stress gradient. • At equal mass, the proposed 3D mass reduction method showcases twice the bending stiffness when compared to topology optimization. Mass reduction and strength-to-weight optimisation are of increasing interest in mechanical engineering. Natural materials such as bone face the same challenges and strike an optimal balance between weight and mechanical performance. Several approaches sought to reproduce trabecular bone's mechanical efficiency, for example topology optimisation or cellular materials. These approaches are often restricted by their computational cost or their spatial homogeneity. Here we develop a 3D mass reduction method bio-inspired from trabecular bone that provides both fast computation and stress driven architecture. The mass reduction method is based on a bio-inspired porous pattern. The pattern is locally adapted to the estimated stress in a mechanical part through an algorithm. This results in an optimised porous architecture that mimics the trabecular form-function relationship. This 3D mass reduction method was validated through 3-point bending experiments. At equal mass, the proposed method showed 66 % improvement in bending stiffness compared to a 2.5D bio-inspired method and 111 % improvement compared to a topology optimisation method. Our results demonstrate the potential of the proposed method for strength-to-weight optimisation. It is applicable in various industries to lighten parts, reduce raw material usage, design composite sandwich cores or personalised bone-tissue scaffolds. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel method to produce 3D auxetic metamaterials has been proposed. • The proposed method involved the application of continuous voids with constant cross-sectional area in multiple perpendicular planes. • The potential of using subtractive manufacturing, additive manufacturing, or casing to fabricate these 3D auxetic structures was shown. • Using continuous voids with a diamond shaped cross-sectional area were shown to produce novel 3D auxetic structures. • Nonlinear simulations and experimental testing showed that the Poisson's ratio of these structures is strain independent up to 7% deformation. Prototyping of three-dimensional mechanical metamaterials that exhibit negative Poisson's ratio is usually performed through additive manufacturing. Although this technique has a huge potential, its use to engineer mechanical metamaterials for consumer products is still challenging. In this work, a novel design method is being proposed where 3D auxetic metamaterials can be produced by introducing continuous voids of constant cross-sectional area. Such voids would be inserted at strategic positions in different perpendicular planes of a solid block to obtain a continuous three-dimensional mechanical metamaterial that can exhibit the desired mechanical characteristics. The use of continuous voids to design the 3D meatamaterial makes it possible to use additive manufacturing, subtractive manufacturing as well as casting to produce these systems. The proposed design method is explained by using continuous voids having a diamond shaped cross-sectional area. The resulting group of structures can be described as connected polygons and were found to exhibit a negative or zero Poisson's ratio. The analysed systems were also found to have a strain independent Poisson's ratio up to at least 7% strain. The proposed design method can thus facilitate the availability of three dimensional auxetic metamaterials in the consumer market which to date is conspicuous by their absence. [ABSTRACT FROM AUTHOR]

[Display omitted] • A composite paper was prepared by combining aramid nanofibers, boron nitride nanotubes, and polyethyleneimine. • Elaborating interfacial hydrogen bonds design can optimize the mechanical properties of composite paper. • The composite paper has high thermal conductivity and unique dielectric performance. Aramid paper is ubiquitous in advanced electronics and high-voltage equipment by virtue of their outstanding dielectric properties, mechanical reliability, and thermal stability. However, their limited thermal conductivity still fails to satisfy the stringent demands for heat dissipation in applications with high power and high energy density. Herein, we report a highly thermally conductive composite paper prepared by synergistically combining one-dimensional (1D) aramid nanofibers (ANFs), 1D edge-hydroxylated boron nitride nanotubes (BNNTs), and polyethyleneimine (PEI). The resultant composite paper exhibits high thermal conductivity (9.91 Wm−1K−1), low dielectric loss (<0.01), and ultrahigh electrical breakdown strength (∼334 kV/mm) with an exceptional heat resistance performance. Three-dimensional hydrogen bonding networks were constructed between the ANF framework, PEI, and BNNTs, endowing the composite paper with a superior tensile strength (up to 317 MPa) and Young's modulus (∼7.7 GPa), which are significantly higher than those of the commercial Nomex T410 paper. This research provides important insights into the design and fabrication of multifunctional insulating paper for application in modern integrated electronic and power systems. [ABSTRACT FROM AUTHOR]

Extracellular matrix (ECM) derived from decellularized tissues and organs has been used as a biological scaffold in a variety of pre-clinical and clinical applications. However, the lack of mechanical properties and shape controllability is a drawback. In contrast, synthetic polymers can be easily engineered with good mechanical performance, but they have limited biological functionality. In this study, we explored a new method to electrospun cartilage-derived extracellular matrix (cECM) and polycaprolactone (PCL) composite nanofibrous membranes. The cartilage is a compact tissue for which electrospinning is difficult. To overcome this problem, the cartilage was sliced into pieces, milled into powders, and digested into a looser structure. The cECM/PCL (mass ratio 50:50) hybrid nanofibers appeared to be smooth, thinner, and uniform with enhanced mechanical properties and wettability compared to the electrospun PCL. Meanwhile, the presence of cECM in the cECM/PCL nanofibrous membranes significantly promoted chondrocyte proliferation in vitro and facilitated cartilage regeneration in vivo. All these results indicate that the cECM/PCL nanofibrous membranes fabricated with good mechanical properties and biocompatibility may represent a promising scaffold for cartilage regeneration. Moreover, this work may offer a convenient and cost-effective method to synthesize ECM-based hybrid nanofibrous scaffolds for other tissue applications. Unlabelled Image • A new method to electrospun cECM/PCL hybrid nanofibrous scaffold was explored. • The cECM/PCL scaffold have enhanced mechanical properties and superior wettability compared with PCL alone. • the cECM/PCL scaffold promoted chondrocyte proliferation in vitro and facilitated cartilage regeneration in vivo. • This method represents a platform in which different decellularized tissues could be electrospun into nanofibers. [ABSTRACT FROM AUTHOR]