A major goal in materials science is to develop bioinspired functional materials based on the precise control of molecular building blocks across length scales. Here we report a protein-mediated mineralization process that takes advantage of disorder–order interplay using elastin-like recombinamers to program organic–inorganic interactions into hierarchically ordered mineralized structures. The materials comprise elongated apatite nanocrystals that are aligned and organized into microscopic prisms, which grow together into spherulite-like structures hundreds of micrometers in diameter that come together to fill macroscopic areas. The structures can be grown over large uneven surfaces and native tissues as acid-resistant membranes or coatings with tuneable hierarchy, stiffness, and hardness. Our study represents a potential strategy for complex materials design that may open opportunities for hard tissue repair and provide insights into the role of molecular disorder in human physiology and pathology.

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This paper proposes an in-situ Structural Health Monitoring (SHM) method able to locate the impact source and to determine the flexural Lamb mode A 0 velocity in composite structures with unknown lay-up and cross-section. The algorithm is based on the differences of the stress waves measured by six surface attached acoustic emission piezoelectric (PZT) sensors and is branched off into two steps. In the first step, the magnitude of the Continuous Wavelet Transform (CWT) squared modulus, which

Any industrial application aiming at exploiting the exceptional properties of graphene in composites or coatings is currently limited by finding viable production methods for large volumes of good quality and high aspect ratio graphene, few layer graphene (FLG) or graphite nanoplatelets (GNP). Final properties of the resulting composites are inherently related to those of the initial graphitic nanoparticles, which typically depend on time-consuming, resource-demanding and/or low yield liquid exfoliation processes. In addition, efficient dispersion of these nanofillers in polymer matrices, and their interaction, is of paramount importance. Here we show that it is possible to produce graphene/epoxy nanocomposites in situ and with high conversion of graphite to FLG/GNP through the process of three-roll milling (TRM), without the need of any additives, solvents, compatibilisers or chemical treatments. This readily scalable production method allows for more than 5 wt % of natural graphite (NG) to be directly exfoliated into FLG/GNP and dispersed in an epoxy resin. The in situ exfoliated graphitic nanoplatelets, with average aspect ratios of 300-1000 and thicknesses of 5-17 nm, were demonstrated to conferee exceptional enhancements in mechanical and electrical properties to the epoxy resin. The above conclusions are discussed and interpreted in terms of simple analytical models.

Ultrasonic waves are useful tools to characterize the contact forces between components in non-destructive and non-invasive manners. It has been shown that the transmission and reflection coefficients of the ultrasonic wave are sensitive to the contact pressure or other contact parameters. Theoretically, the normal and tangential stiffnesses of the contact interface govern the transmission/reflection coefficients and can be used as parameters to characterize the contact condition. However, weak and incomplete interfaces, formed by rough surfaces in partial contact, show a highly nonlinear behaviour also when they are excited under free vibrations. In particular, the amplitude of the second harmonic is a relevant index of the contact stiffness, and the nonlinear response is strongly influenced by the nominal contact pressure applied to the boundaries. In this study a new theoretical model of the nonlinear interface stiffness was developed where the stiffness of the contact interface was described as a function of the nominal contact pressure. The developed theoretical contact pressure function of the second harmonic generation at the contact interface was found to agree with good accuracy with the experimental data. Moreover, this paper presents also a theoretical and experimental study aimed at developing an integrity index capable of assessing the stiffness of the contact interface between structures when excited by free vibration or under controlled vibration excitation.

We present a micromechanical analysis of flow-induced peeling of a layered 2D material suspended in a liquid, for the first time accounting for realistic hydrodynamic loads. In our model, fluid forces trigger a fracture of the interlayer interface by lifting a flexible "flap" of nanomaterial from the surface of a suspended microparticle. We show that the so far ignored dependence of the hydrodynamic load on the wedge angle produces a transition in the curve relating the critical fluid shear rate for peeling to the non-dimensional adhesion energy. For intermediate values of the non-dimensional adhesion energy, the critical shear rate saturates, yielding critical shear rate values that are drastically smaller than those predicted by a constant load assumption. Our results highlight the importance of accounting for realistic hydrodynamic loads in fracture mechanics models of liquid-phase exfoliation.

A new enriched weight function for meshless methods is proposed for the numerical treatment of multiple arbitrary cracks in two dimensions. The main novelty consists in modifying the weight function with an intrinsic enrichment which is discontinuous over the finite length of the crack, represented by a segment, but continuous all around the crack tips. An analytical function is used to introduce discontinuities that are incorporated in the kernel in a simple, multiplicative manner.The resulting method allows a more straightforward implementation and simulation of the presence of multiple cracks, crack branching and crack propagation in a meshless framework without using any of the existing algorithms such as visibility, transparency, and diffraction and without using additional unknowns and additional equations for the evolution of the level-sets, as in extrinsic partition of unity-based methods.Stress intensity factors calculated using the J-integral demonstrate excellent agreement with analytical solutions for classical fracture mechanics benchmarks.Recently, two classes of methods have promisingly overcome these limitations for fracture mechanics: extended finite elements (XFEM) [5,6] and meshfree methods [7]. Both methods are particular instances of the more general class of partition of unity methods [8]. XFEM is based on an extrinsic Partition of Unity (PU) enrichment (generally a Heaviside function and the asymptotic crack-tip fields) that introduces additional unknowns, whereas meshfree methods such as those based on the moving least squares (MLS) approximation, might not necessarily need additional unknowns to represent discontinuities [9][10][11][12]. In the MLS method, shape functions are corrected versions of compact supported weight functions (sometimes called kernel) centered in each node of the discretization.Extensive literature exists for meshfree methods: application of these techniques have been quite successful in the recent years, especially in problems with discontinuities and singularities, and a large number of papers can be found which dealt with these questions [7,9,11,[13][14][15][16][17][18]. A good number of review papers [15,19,20] and books [21] on meshfree methods have been published in the recent years. Updated reviews on meshfree methods can be found in [22] and [23].Recent advances in the context of fracture mechanics using meshfree methods comprise coupling with fractal elements [24] and applications to graded materials [25], but particularly notable is the cracking particles method [26]. In this method, each crack is not considered continuous, instead is modeled by a contiguous set of cracked particles, removing the need of representing the crack surface explicitly. As a consequence, the resulting crack path is discontinuous; nonetheless the method is simple and effective and has been successfully applied to three-dimensional problems [27].Recently, there have been a number of works that suggested the use of enriched weight functions [28][29][30] rather than basis enrichment....

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