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Penta-graphene is a new two-dimensional metastable carbon allotrope composed entirely of carbon pentagons with unique electronic and mechanical properties. In this work we evaluate the mechanical properties of new classes of defective penta-graphene (DPG) subjected to tensile and shear loading by using molecular dynamics simulations. The types of defects considered here are monovacancy at either 4-coordinated C1 site or 3-coordinated C2 site, and double vacancy (DV). We focus in particular on the effects of the different topologies of defects and their concentrations on the elastic constants and the nonlinear mechanics of this allotropic form of carbon. The results indicate that DPG has a plastic behavior similar to pristine penta-graphene, which is caused by the irreversible pentagon-to-polygon structural transformation occurring during tensile and shear loading. The tensile and shear moduli decrease linearly with the concentration of defects. Monotonic reductions of the tensile yield and shear stresses are also present but less pronounced, while the yield strains are unaffected. Penta-graphene with 4-coordinated and DVs feature a change of the Poisson's ratio from negative to positive when the defect concentration rises to about 3% and 6%. Temperature can trigger structural reconstruction for free-standing DPG. The critical transition temperature increases due to the vacancy defects and the defects can delay the structure transition. These findings are expected to provide important guidelines for the practical applications of penta-graphene based micro/nano electromechanical systems. [ABSTRACT FROM AUTHOR]

Rigid polyurethane foams (RPUFs) are among the most used polymeric materials due to their tailorable properties. Greener and biobased polyol sources for synthesising RPUFs have been recently prototyped because of the ever-growing demand for more sustainable materials solutions. Castor Oil has also rapidly become one of the most successful alternatives to replace polyurethane fossil-based components. This study extensively investigates three types of RPUFs developed from commercially available Castor Oil-based resins, correlating their properties across different length scales. In particular, X-ray diffraction identified a characteristic peak whose intensity correlated with the apparent foam density, morphology (obtained from computed tomography scans) and mechanical properties. Furthermore, quasi-static compression and vibration transmissibility tests revealed distinctive anisotropic mechanical responses among the foams, with one type of RPUF consistently outperforming the others due to its lower porosity, reaching 13.3 MPa of compressive modulus. These findings demonstrate the possibility of tuning the mechanical properties of foams via compositional control. • Extensive characterisation of Castor Oil-based rigid polyurethane foams. • Foam morphology and mechanical properties can be tuned via composition control. • Correlation of the foam's XRD pattern with porosity and density. [ABSTRACT FROM AUTHOR]

In this work, a mathematical formulation based on variational asymptotic method (VAM) has been proposed to determine the effect of damage on the auxetic properties of two-dimensional (2D) and three-dimensional (3D) re-entrant geometries. The influence of damage progression on the auxetic behavior was captured using a geometrically exact one-dimensional beam theory and an isotropic damage law, implemented in a nonlinear finite element framework. The effect of material degradation on the macroscale effective elastic properties such as the elastic modulus and Poisson's ratio for the two-dimensional and three-dimensional re-entrant auxetic geometries was quantified. The mechanical behavior as predicted by the in-house Python-based implementation of the proposed VAM-based formulation is verified with the results from the commercial finite element solver Abaqus, wherein the user material subroutine was used to capture damage evolution. The numerical examples presented in this paper reveal that the macroscale auxetic behavior of the geometries was affected significantly by damage progression. The results of this research will provide insights into the design and analysis of auxetic materials for applications that warrant consideration of damage evolution. • A mathematical formulation based on variational asymptotic method has been proposed to determine the effect of damage on the auxetic properties of 2D and 3D re-entrant geometries. • The influence of damage progression on the auxetic behavior was captured using geometrically exact one-dimensional beam theory and an isotropic damage law, implemented in a nonlinear finite element framework. • The numerical results provide insights into the design and analysis of auxetic materials for applications that warrant consideration of damage evolution. [ABSTRACT FROM AUTHOR]

[Display omitted] • The flexural modulus of sandwich panels can be estimated by the homogenisation concept. • Underestimated flexural modulus is experimentally obtained under the occurrence of shear deformations. • Advised classifications for core rigidity: very high, non-negligible, and negligible. • R J S ¯ factor reports the flexural rigidity of the core, and R J S ∗ factor the shear one. • The greater the R J S ∗ factor, the lower the span length should be to nullify shear effects. The primary RJS Method consists of a suggestive criterion for the qualitative and quantitative classification of the core rigidity relevance in sandwich panels based on the structure's ability to achieve pure bending behaviour. It also includes a set of assumptions that address the influence of the dimensions of the specimen on the elastic properties measured by three-point bending tests. The method allows for characterising the flexural modulus of sandwich panels through a homogenisation concept and comparing theoretical and experimental values to assess the amount of shear deformations occurring. Some limitations of the method were reported, such as the restriction to three-point bending tests and symmetrical sandwich structures (those composed of faces of the same thickness and composition). Additionally, the possible contribution of the rigidity of the face-to-core adhesives was not addressed when estimating the overall rigidity of a sandwich panel. Moreover, a direct link between the qualitative and quantitative classifications of core rigidity relevance was not achieved. In this new enhancement approach, called the RJS Method 2.0, not only are faces of different thicknesses and compositions addressed, but also the mechanical contribution of the face-to-core bonding when adhesives with relative thickness and rigidity are used. The new equations also cover four-point bending tests and clarify a direct association between the qualitative and quantitative classifications of core rigidity relevance. To facilitate the theoretical calculation of all equations, a MATLAB script is proposed. The outputs of the script are thoroughly compared to numerical results and data available in the literature, demonstrating the proper accuracy of the RJS Method 2.0 in predicting the elastic properties of sandwich structures under bending. [ABSTRACT FROM AUTHOR]

• Cellular structure design biomimicking the core of the beetle. • First full exploration of the out-of-plane engineering elastic constants of beetle-elytra inspired cores. • First transverse shear tests on these beetle-elytra inspired cores carried out according to ASTM standard. • Rigorous parametric analysis of the properties via representative volume elements (RVEs) homogenization techniques. The Beetle Elytron Plate (BEP) is a new type of biomimetic sandwich core developed as a potential replacement of classical honeycomb cores in sandwich panels. This work investigates the out-of-plane engineering elastic constants, including Young's and pure shear moduli of parametric BEP cellular topologies. The BEP core configurations are simulated using Finite Element models, with both full-scale and representative unit cells for asymptotic homogenization. The numerical models are also validated by flatwise compression and out-of-plane pure shear loading experiments performed according to ASTM standards. The benchmarked models are then used to perform a parametric analysis of the beetle elytra cellular cores against their geometry characteristics. Results show that the out-of-plane Young's modulus E 3 / E s and the transverse pure shear modulus G 31 / E s of both BEP configurations are larger than those of the classic hexagonal honeycombs and increase when the size of the unit cell cylinders, or rib thickness become large. The specific shear moduli of the beetle-elytra inspired honeycombs are however lower than those of classical pure hexagonal honeycomb configurations, although the added presence of cylinders within the cell configuration offers opportunities for tailoring the design of multifunctional cores. [ABSTRACT FROM AUTHOR]

This work describes the low-velocity impact behavior of composite sandwich panels with different types of auxetic (negative Poisson's ratio) and non-auxetic prismatic core structures. Sandwich panels have been manufactured with carbon/fiber epoxy composite face sheets, polyurethane rigid foam core or 3D printed PLA plastic cellular honeycombs head (hexagonal, re-entrant, hexachiral and arrowhead). The material properties of the constituents have been determined via tensile and compression tests. The cellular core topologies have the same wall thickness and number of cells (39x4, except for the hexachiral topology). A rigid striker with a hemispherical head tip is dropped on the specimens with a speed of 2.6 m/s. Explicit finite element (FE) models are validated by the experimental results. Parametric numerical analyses using the validated FE have been carried out with different impact energies of 10, 20, 30, 40, 50, 60 and 76 J to identify the best core designs. The results show that non-auxetic cores could have advantages over the auxetic ones at small deformation (impact energy is equal to 10 J) thanks to the larger contact surface and higher thickness of the cellular structure. The auxetic core, however, provides greater impact resistance and energy absorption capability as the impact energy increases due to the larger densification and lower indentation during collapse. The arrowhead-based panels in particular possess 25%, 13% and 11% larger crash efficiency than the other samples for impacts with 50, 60 and 76 J. The hexachiral lattice provides the best performance at 10, 20 and 30 J, and also possesses advantages over the other cellular configurations (except for the arrowhead core) in the case of 40, 50, 60 and 76 J impact loading. As a result, the arrowhead and hexachiral configurations are those mostly recommended for applications involving impacts under large deformations. • Polyurethane foam and PLA plastic cellular honeycombs are used as core material for composite sandwich panels. • Auxetic core design could provides greater impact resistance and energy absorption capability. • Non-auxetic cores could have advantages over the auxetic ones at small deformation. • Arrowhead and hexachiral honeycomb cores are mostly recommended under impact loading. [Display omitted] [ABSTRACT FROM AUTHOR]

This work describes the in-plane uniaxial tensile mechanical properties of two-dimensional graded rectangular perforations metamaterials using numerical homogenization finite element approaches benchmarked by experimental results. The metamaterial configuration is based on graded patterns of centre-symmetric perforated cells that can exhibit an auxetic (negative Poisson's ratio) behavior. Global and local equivalent mechanical properties of the metamaterial are measured using digital image correlation techniques mapped over Finite Element models to identify strain patterns and related stress distributions at different scales. The samples and their numerical counterpart are parametrized against the spacing and aspect ratios of the cells. The overall stiffness behavior of the graded perforated metamaterial plates features a higher degree of compliance that depends both on the geometries of the cells of the graded areas, but also on the graded pattern used. Local Poisson's ratio effects show a general constraint of the auxetic behavior compared to the case of uniform plates, but also interesting and controllable shape changes due to the uniaxial tensile loading applied. [ABSTRACT FROM AUTHOR]

Morphing wingtip technology could improve the reduction of the induced drag, fuel consumption, and take-off and landing distances in fixed wing configurations. We describe in this work a morphing winglet concept based on active inflatable honeycombs and Shape Memory Polymer Composite (SMPC) skins. The combination of the two materials and structural subsystems allow the winglet deployment, with a morphing skin able to withstand the aerodynamic loading, also through the use of distributed pneumatic muscle fibers. An actuation geometric and mechanical model that represents the morphing wingtip concept is developed and analyzed. A morphing wingtip prototype is also fabricated to demonstrate the kinematics and actuation of the concept. Experiments and simulations show agreement about the output angle/input pressure relationship necessary for the wingtip deployment. [ABSTRACT FROM AUTHOR]

This study focuses on the chemical and thermo-physical characterization of date palm fiber, which can be used in the reinforcement of green composites. Alkaline solutions with different concentrations of NaOH (0.5, 1, 2 and 3%) and various immersion times (0.5, 1, 2, 4, 6 and 8h) at room temperature were used to treat fibers obtained from date palm fruit branches. In total, 750 samples were tested, and the results obtained show that the chemical treatment of the fibers can lead to an increase, up to 3 times, of their mechanical properties (strength and Young's modulus) in quasi-static tensile tests. Due to the dispersion in the experimental data, a statistical approach is required to evaluate the mechanical properties. To better understand the phenomena related to the physico-chemical properties of these fibers, several characterization techniques have been used, namely Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray diffraction. The data have been compared with results reported in the literature for other lignocellulosic fibers. [ABSTRACT FROM AUTHOR]

We present in this paper two novel concepts of hybrid metamaterials that combine a core unit cell of re-entrant or cross-chiral shape and lateral missing ribs. The first topology is a hybrid between an anti-tetrachiral and a missing rib (cross-chiral) configuration; the second one has a variable cross-chiral layout compared to the classical missing rib square structure. Their in-plane mechanical properties have been investigated from a parametric point of view using finite element (FE) simulations. The two classes of metamaterials have been benchmarked to obtain optimized designs and specific effective properties. Nonlinear simulations and experimental tests of the new re-entrant missing rib metamaterials featuring optimized geometry parameters have been performed to understand the behavior of these architectures under large deformations. • Two novel hybrid metamaterials combining a core unit cell of re-entrant or cross-shape and lateral ligaments are proposed. • In-plane mechanical properties of the two metamaterials are parametrically investigated using finite element method. • Nonlinear simulations and experiments of the new re-entrant missing rib metamaterial with optimized feature are performed. [ABSTRACT FROM AUTHOR]

• Quasi-static and cyclic fatigue traction of long fibers of date palm fruit branches. • Characterization by SEM of the fiber of date palm fruit branches. • Analysis of load-displacement hysteresis curves. • Interpretation and discussion of S-N curves. This work describes the quasi-static tensile behavior and cyclic fatigue of technical fibers from date palm tested for the first time according to the authors' knowledge, which can be used in the reinforcement of green composites.The values of the stress and strain at failure and Young's modulus for18 samples tested under quasi-static tensile loading are compared with results reported in the literature for other fibers. Cyclic fatigue tests were performed at a frequency of 2 Hz under sinusoidal solicitation for different loading levels ranging from 0.6 to 0.95 corresponding to maximum recorded forces of 15.36 and 39.82 N, respectively. The evolution of the force as a function of the number of cycles was recorded. This allows us to follow the stiffness degradation. The load-displacement hysteresis curves show the influence of the number of cycles and the loading level on the size and shape of the hysteresis loops, allowing the calculation of the dissipated energy per cycle for the technical fibers. [ABSTRACT FROM AUTHOR]

This work describes aluminium skin sandwich panels made of recycled polyethylene (PE) bottle caps as a sustainable honeycomb core. A full factorial design is carried out to identify the effects of the orientation of the caps (single and alternated caps), skin roughness (smooth and rough substrate) and the type of adhesive (epoxy or polyester polymer) on the mechanical properties of the panels. Numerical analysis is performed to better assess the failure mechanisms involved. Sandwich panels made with epoxy adhesive, smooth aluminium skin and single oriented caps obtain greater mechanical properties at failure compared to the alternative levels of the factorial design. Increased results are observed for core shear stress (0.38 MPa), facing stress (56.75 MPa), core shear modulus (16.70 MPa), and flexural modulus (1437.47 MPa). This performance reveals an alternative recycling route for used PE bottle caps in structural and sustainable applications. [ABSTRACT FROM AUTHOR]

Herein, the effect of symmetric carbon fiber composites laminates with angle‐ply stacking sequences ([±β/±θ]S) in the design of composite piezoelectric energy harvesters (PEHs) is evaluated. Some of those specific stacking sequences also feature negative Poisson's ratio (NPR) or near zero Poisson's ratio (NZPR) through the thickness for ply angles θ < 45°. Six different architectures with similar in‐plane elastic modulus E1 and different positive Poisson's ratio and NPR v13 values are considered here. Finite element models are developed to understand the distribution of the voltage density of the laminates with the different stacking sequences and their bending properties. Experimental tests (three‐point bending and vibration) are also performed. Both the simulations and the experimental results show that the PEH with the stacking sequences of near zero v13 generate the highest power compared with the other composite energy harvesters. The maximum voltage frequency response function (FRF) happens at the fundamental resonance, and the PEH with near zero v13 has also the lowest resonance frequency compared with the other stacking sequences. [ABSTRACT FROM AUTHOR]

In this work, we propose a new type of thin-walled energy-absorbed structure with hollow columns that possesses a design inspired by the beetle elytra. The failure mode of the bionic thin-walled structures is firstly discussed by developing a theoretical model. The energy absorption properties of these bio-inspired multi-cell thin-walled structures have been then investigated using nonlinear finite element simulations. The values of the specific energy absorption and the crushing force effectiveness have been evaluated for different structures with parametrized column nested configurations. Dynamic impact simulations of multi-cell tubes with different columns nested modes, wall thickness and impact angles have been performed, and the results discussed. [ABSTRACT FROM AUTHOR]

Phononic metamaterials are capable of manipulating mechanical wave propagation in applications ranging from nanoscale heat transfer to noise and vibration mitigation. The design of phononic metamaterials to control low-frequency vibrations, such as those induced by ground transportation and low-amplitude seismic waves, however, remains a challenge. Here we propose a new design methodology to generate seismic metamaterials that can attenuate surface waves below 10 Hz. Our design concept evolves around the engineering of the multi-layered soil, the use of conventional construction materials, and operational construction constraints. The proposed seismic metamaterials are constructed by periodically varying concrete piles in the host multi-layered soil. We first validate the design concept and the numerical models by performing a lab-scale experiment on the low-amplitude surface wave propagation in a finite-size seismic metamaterial. To the best of the Authors' knowledge, this is one of the few attempts made to date to experimentally understand the vibration mitigation capability of seismic metamaterials. We then numerically demonstrate that the multi-layered seismic metamaterials can attenuate surface waves over a wide frequency range, with the incident wave energy being confined within the softest layer of the shallow layered seismic metamaterials. In addition to the localized wave energy distribution, deep layered seismic metamaterials exhibit broadband cut-off band gaps up to 7.2 Hz due to the strongly imposed constraint between piles and surrounding soil. Furthermore, these cut-off band gaps strongly depend on the constraint between the piles and the bottom layer of the soil and hence can be tuned by tailoring the foundation stiffness. We also evidence the possibility to create constant wave band gaps by introducing hollow concrete piles with pile volume fraction <10% in the deep layered seismic metamaterials. The findings reported here open new avenues to protect engineering structures from low-frequency seismic vibrations. Unlabelled Image • Lab scale experiments were conducted to understand elastic wave propagation in seismic metamaterials. • Finite element models for wave propagation analysis were validated against the experiments. • Multi-layered seismic metamaterials can attenuate surface waves by confining wave energy. • Broadband cut-off band gaps up to 7.2 Hz were predicted in the multilayered seismic metamaterials. [ABSTRACT FROM AUTHOR]

A methodology to perform the probabilistic and reliability-based design of a novel carbon/carbon rocket nozzle subjected to operational thermal and mechanical loads is described in this paper. In this methodology, the nozzle is represented by a multiphysics finite element model capable of predicting the temperature and stress fields of the exit cone. The analysis shows that the most likely failure modes of the exit cone are related to compressive stress along the axial and hoop directions, as well as interlaminar shear. The probabilistic models used in this methodology account for the uncertainty of the material properties by using uniform and normal distributions and different variances. The reliability analysis is performed by using surface response methods. A global sensitivity analysis is also carried out using polynomial expansion chaos surface response models. A particular novelty of the analysis is the use of Sobol indices to rank the importance of the single uncertain parameters in the models. The methodology provides a high level of confidence and robustness in determining that the axial thermal conductivity of the carbon/carbon material is the most critical material property to affect the three main failure modes, whereas the coefficient of the thermal expansion and the heat capacity play a very marginal role. [ABSTRACT FROM AUTHOR]

Abstract This work focuses on entangled wire materials as an option for use between segments of a novel self-centring bridge pier inspired from the human spine mechanism to increase energy dissipation capability of the pier in rocking. A comprehensive set of free-decay vibration tests was conducted on small-scale columns with and without entangled wire materials. Wooden blocks are used as vertebrae with entangled wire materials as intervertebral disks. The whole system is tied together using a pre-tensioned tendon. Dynamic properties of columns (i.e. frequency and damping ratio) were then identified and compared. It is found that the use of entangled wire materials significantly increases the energy dissipation capacity of the system during rocking. This finding is very encouraging for future use of entangled wire materials composite systems in large-scale testing of the proposed rocking column, while their shear and axial stiffness needs be improved to reduce large shear and axial deformations. [ABSTRACT FROM AUTHOR]

Abstract In recent years, studies of composite materials have focused on the use of natural fibres as an alternative to synthetic ones. Their attractive mechanical properties, sustainability, low cost and low weight have leveraged research in this area, with the potential of a variety of applications in the engineering field. In this paper, a Full Factorial Design (2161) experiment was performed to identify the effect of silica microparticle inclusions and the stacking sequence of glass fibre cross-ply fabric and short sisal fibre layers on the apparent density, tensile and flexural strength and modulus of hybrid epoxy composites. In general, the hybrid composites with higher number of glass fibre layers achieve higher values of tensile and flexural strength (348 MPa and 663.28 MPa), tensile and flexural modulus (22 GPa and 2.50 GPa) and higher apparent density (2.02 g/cm³). It is, however, noteworthy that the incorporation of silica particles improves the mechanical performance of composites containing larger amounts of sisal fibres. Highlights • A single-layer inclusion of glass fibre leads to enhanced mechanical properties. • Silica inclusion leads to increased stiffness especially in large amounts of sisal fibres. • A delamination effect under bending is more evident for the hybrid structure. • Random short sisal composites reveal fibre pull-out effect under bending. • 2S3G composites without silica particles achieve moderate strength and stiffness. [ABSTRACT FROM AUTHOR]

Abstract The paper describes the impact behaviour of hybrid composites made of sugarcane bagasse fibres and disposed rubber particles. The analysis was carried out using a full factorial design (25) on samples subjected to drop-tower testing. The effects of the bagasse fibre treatment, length and weight fraction were considered, as well as the rubber particles size and their amount. Higher weight fractions of coarse rubber particles led to an enhancement of the absorption. Sustained chemical treatments of the bagasse fibres provided an increase of the composites stiffness, reducing therefore the energy absorption. In contrast, higher energy absorption was obtained in composites made with untreated bagasse because of the enhanced fibre pull-out mechanism. [ABSTRACT FROM AUTHOR]

Abstract This paper studies the feasibility of improving structural performance of composites in the presence of stress concentrators. Matrix grading through local deposition of additive-enhanced matrices and fibre steering by varying fibrous architecture are examined independently and in combination on a glass-fibre triaxial braided composite subjected to open hole tensile test. Stiffened and toughened matrices were incorporated through precise point-wise injections of liquid reactive resin into dry preforms (Liquid Resin Printing). Fibre steering was implemented by varying the braiding angle along the length of the braided sleeve. It has been shown that these novel forms of architecture modification enable a significant improvement in composite strength through a variety of deformation mechanisms. This includes local stiffening of composite in the direct vicinity of the stress concentrator and damage accumulation away from the stress concentrators. The experimental observations are explained by using simple finite-element models. [ABSTRACT FROM AUTHOR]

Adaptive wings configurations have been evaluated for morphing airframe applications during the last two decades. Constructions with flexible hinges can be in particular a solution for small top medium-scale air vehicles, while novel Kirigami technologies help to produce flexible and complex structures by enabling novel geometric paradigms. In this study, a cellular Kirigami wingbox with an adaptive hinge is designed and manufactured. The mechanical properties of the wingbox are numerically evaluated, considering the shear modulus of the cellular elements patterning the wingbox. Thus, the equivalent torsional, flexural stiffness, as well as the shear center location of the whole wingbox structure are calculated. The analysis is parametrized against various possible internal cell angles and cell thickness values that define the Kirigami cellular tessellation of the wingbox. The static divergence speed is also evaluated by means of the same parametrization. This study shows the feasibility of using a Kirigami wingbox concept for morphing/adaptive small to medium-scale from a structural and aeroelastic perspective. [ABSTRACT FROM AUTHOR]

[Display omitted] • A bio-inspired coating technology is proposed to develop multifunctional porous metal materials. • The coating simultaneously significantly enhances the mechanical, damping, and sound absorption capabilities of nickel foam. • The coating maintains high enhancing performance in high-temperature environment. Graphene coating on the skeleton of porous material opens the door to simply achieving high-performance composites. In this study, relying on the adhesive properties of polydopamine (PDA), PDA modified reduced graphene oxide (PDA-rGO) is adhered to the skeleton of nickel foam, of which the mechanical properties as well as the vibration damping and sound absorption performances are investigated. The mechanical test results reveal that the existence of coating leads to 240% and 59% increments of the compressive modulus and the yield strength, respectively. The enhancement of dynamic mechanical properties is also verified by dynamic mechanical analysis (DMA). Moreover, in DMA tests, the loss factors of nickel foam coated with PDA-rGO are found to achieve up to 170% growth, and show excellent stability with increasing temperature, indicating the reliability of loss factor enhancement in harsh environment. The superior vibration damping performance of nickel foam coated with PDA-rGO is further confirmed by vibration tests. Furthermore, the coating is found to effectively boost the flow-resistance and improve the sound absorption capability of nickel foam in turn, this synergy results in a significant increase in the noise reduction coefficient for up to 73.3%. Hence, adhering PDA-rGO to nickel foam in the present study provides a promising strategy for the development of multi-functional and versatile metallic foam. [ABSTRACT FROM AUTHOR]

[Display omitted] • Design of polyurethane foam composites with naturally abundant sepiolite nanoclay and biopolymer chitosan via simple and facile layer-by-layer coatings. • The coatings reinforce the foam skeleton, resulting in a 200% improvement of the Young's and dynamic moduli compared to untreated foams. • Transmitted impact forces are reduced by 50% with six bilayer coatings, demonstrating an improved impact energy dissipation. • Detailed discussions are provided about the deformation mechanisms and enhancement of the quasi-static and dynamic mechanical performance. Flexible polyurethane foam composites with enhanced stiffness and energy dissipation have been prepared via a facile layer-by-layer assembly approach. The composite foams consisted of naturally abundant nanoclay/chitosan multilayers (up to six) deposited onto the foam struts via dip-coating. The nanoclay/chitosan polyurethane foams were characterised using infrared spectroscopy, scanning electron microscopy, elemental mapping and μ-CT scanning. Quasi-static mechanical compression of the foams with 6 bilayers showed a 202% increase in the stiffness and a 33% enhancement in the damping loss factor compared to the uncoated pristine foam. Vibration transmissibility tests showed that the dynamic modulus of the 6-bilayer coated foams was 3 times that of the pristine foam. Remarkably, impact tests registered a 50% decrease in the transmitted impact force of these sepiolite/chitosan layer-by-layer coated open cell polyurethane foams, demonstrating their improved energy dissipation capability compared to other nanocoated foams in open literature. [ABSTRACT FROM AUTHOR]

Abstract A tensegrity structure involves the presence of elements withstanding pure compression, and others under pure tension only. Metal rubber is introduced into a tensegrity prism strut to create a mechanical metamaterial with energy absorption and tuneable dynamic properties. In this work we describe the design and development of the meta -tensegrity structure with particular emphasis on the evaluation of parameters such as the structural size, the metal rubber stiffness, the initial internal force and the external compression load. Prototypes of tensegrity prisms with and without metal rubber inserts have been assembled and subjected to quasi-static loading. The model used to design the meta tensegrity prism has been then modified to take into account specific manufacturing and internal dissipation mechanisms typical of this configuration. The updated model provides a better comparison with the experimental results. Both the theoretical and experimental data show that the introduction of the metal rubber within the tensegrity configuration contributes to improve significantly the energy absorption, and to reduce the stiffness of the whole tensegrity structure. [ABSTRACT FROM AUTHOR]

Abstract The apparent density, flexural modulus and strength of hybrid laminated composites were investigated through a full-factorial Design of Experiment (DoE) approach. Laminates were manufactured by hand lay-up using nine layers of glass fibre cross-ply fabric with an epoxy matrix phase reinforced with Portland cement microparticles. A first experiment investigated the effect of the inclusion site (particles in upper four layers, lower four layers, all layers or none), curing time (7 and 28 days) and compaction method (vacuum or uniaxial pressure). The fibre–matrix volume fraction and the particle mass fraction were fixed at 48.6/51.4% and 10% respectively. A second experiment investigated two distinct fibre–matrix volume fractions (48.6/51.4 and 29.6/70.4%) and five particle mass fractions (0, 2.5, 5.0, 7.5 and 10 wt%). Particle inclusions were restricted to the upper four layers, with 28 days of curing time and uniaxial compaction. The results were analysed via Analysis of Variance (ANOVA). A significant increase in flexural modulus and strength was observed at 28 days of curing time. Enhanced mechanical properties were obtained for laminates with particle inclusions only in the upper half of the structure, manufactured with 48.6/51.4% fibre-matrix volume fraction and uniaxial pressure. Higher flexural strength was achieved for composites manufactured with 51/49% fibre–matrix volume fraction and 2.5% of particle mass fraction. These fibrous-particulate hybrid composite laminates can be considered for future secondary structural parts in lightweight engineering applications. [ABSTRACT FROM AUTHOR]

Abstract A full factorial design (2231) has been used to investigate the effect of the use of sodium hydroxide fibre treatment, Portland cement and uniaxial pressure on the physical and mechanical properties of hybrid short coir fibre reinforced composites (HSCoirFRCs). The response variables considered in this work were the apparent density, porosity, tensile and flexural strength, the modulus of elasticity and the Charpy impact resistance. The alkali treatment contributed not only to reduce the apparent porosity, but also to increase the mechanical properties of the HSCoirFRCs. A reduction of the impact resistance and an increase of the apparent density was also identified after treatment. Cold pressing significantly affected the physical and mechanical properties of the HSCoirFRCs. Higher pressure levels enhanced the wettability of the fibres and, consequently, the mechanical performance of the composites. The incorporation of cement microparticles as a second reinforcement phase was however not effective, leading to decreased strength and an increased apparent density of the materials. The HSCoirFRC structure can be considered an economical and sustainable alternative for future secondary structural parts in lightweight transport applications. [ABSTRACT FROM AUTHOR]

The paper describes the identification and optimization of unbalance parameters in rotor-bearing systems. Two methods are proposed for the identification of the unbalance characteristics: the first is based on modal expansion combined with the use of optimization algorithms, while the second relates to the use of modal expansion technique applied to the inverse problem. In this work, the modal expansion technique is used to overcome the issue related to the use of a reduced number of measuring points. The equivalent unbalance forces can then be estimated by expanding the modal displacements into generalized coordinates of the equations of motion of the rotor system. An error due to the use of a modal expansion is however inevitable, and to solve the issue we propose the adoption of an inverse problem formulation to avoid the computation of the displacements at each measurement point. The axial location of the unbalance must be however known in advance, if the inverse problem approach is used to identify the unbalance parameters. We therefore propose in this work an integrated modal expansion/inverse problem methodology combined with an optimization procedure. The technique allows to identify the axial location of the unbalance, its magnitude and phase. Simulation and experimental investigations are carried out to verify the validity of the proposed methods in a double-disk rotor-bearing system. The results show that identification and optimization procedure for the integrated modal expansion/inverse problem approach provides more accurate predictions than the ones given by the pure modal expansion method. [ABSTRACT FROM AUTHOR]

The hybrid configuration of bio-reinforced composites has established a new extended boundary for the development of pro-ecological technologies due to light weight, moderate specific strength, low cost, environmental benefits, and potential applications of natural components. This work investigates the physical and mechanical properties of hybrid composites made of sisal/glass fibres and Portland cement inclusions. A full factorial design was generated to identify the effects of the stacking sequence and cement particles on the flexural strength, flexural stiffness, apparent density, apparent porosity and water absorption of the composites. The significant contributions of these main factors and their interactions were determined via Design of Experiments (DoE) and Analysis of Variance (ANOVA). The fracture features and damage mechanisms of hybrid composite were also reported. The inclusion of cement microparticles led to an increased apparent porosity, as well as enhanced water absorption, flexural stiffness and flexural strength of the hybrid composites. The mechanical properties were strongly dependent on the fibre stacking sequence, which accounts for approximately 98% of the effects observed. Moreover, the stacking sequence affected the damage mechanism of the bio-composites. Finally, the replacement of glass fibres by unidirectional sisal reinforcements may potentially improve the specific properties in structural applications with an environmental sustainable footprint. [ABSTRACT FROM AUTHOR]

This work further investigates the manufacture and characterisation of a sustainable sandwich panel made from aluminium skins and a recycled thermoplastic bottle cap core, an innovative concept proposed in a previous paper. A full factorial design based on Design of Experiments (DoE) and Analysis of Variance (ANOVA) techniques has highlighted the complex influence of three manufacturing parameters (type of polymeric adhesive, adhesive layer thickness layer and core packing topology) on the absolute and specific physical and flexural properties of the panels. The ANOVA revealed that the use of higher amount of epoxy polymer led to enhanced panel strength and stiffness. The cell packing topology, however, did not provide a significant effect on most panel properties. Discarded bottle caps have proven to be a promising lightweight and inexpensive honeycomb component for structural applications. [ABSTRACT FROM AUTHOR]

We present here a design of the unit cell of a mechanical metamaterial based on the use of a tensegrity structural configuration with a metal rubber. Tensegrity combines the use of compression and tension-only elements, and allows the creation of structures with high rigidity per unit mass. Metal rubber is a multiscale porous metal material with high energy absorption and vibration damping capabilities under compressive load. The combination of the two structural and material concepts gives rise to a mechanical metamaterial with increased energy absorption and tuneable nonlinearity under quasi-static, vibration, and impact loading. We develop prototypes, models, and perform tests under static and dynamic loading conditions to assess the performance of this mechanical metamaterial. [ABSTRACT FROM AUTHOR]

Rapid advances in sensing technologies are leading to the development of integrated wearable electronics for biomedical applications. Piezoelectric materials have great potential for implantable devices because of their self-powered sensing capacities. The soft and highly deformable surfaces of most tissues in the human body, however, restrict the wide use of piezoelectric materials, which feature low stretchability. Flexible piezoelectric polyvinylidene fluoride films that could conformably integrate with human bodies would have advantages in health monitoring. Here, a Kirigami technique with linear cut patterns has been employed to design a stretchable piezoelectric sensor with enhanced piezoelectricity. A parametric Finite Element Analysis study is first performed to investigate its mechanical behaviour, followed by experiments. An inter-segment electrode connection approach is proposed to further enhance the piezoelectric performance of the sensor. The voltage output shows superior performance with 2.6 times improvement compared to conventionally continuous electrodes. Dynamic tests with a range of frequencies and strains are performed to validate the sensor design. With its high performance in large strain measurements, the Kirigami-based sensing system shows promise in stretchable electronics for biomedical devices. [ABSTRACT FROM AUTHOR]

We present a lattice structure defined by patterns of slits that follow a rotational symmetry (chiral) configuration. The chiral pattern of the slits creates a series of hinges that produce deformation mechanisms for the lattice due to bending of the ribs, leading to a marginal negative Poisson's ratio. The engineering constants are modeled using theoretical and numerical Finite Element simulations. The results are benchmarked with experimental data obtained from uniaxial and off-axis tensile tests, with an overall excellent agreement. The chiral hinge lattice is almost one order of magnitude more compliant than other configurations with patterned slits and – in contrast to other chiral micropolar media – exhibits an in-plane shear modulus that closely obeys the relation between Young's modulus and Poisson's ratio in homogeneous isotropic linear elastic materials. [ABSTRACT FROM AUTHOR]

Abstract: Aerospace vehicles are subjected to high temperatures because of surrounding aerodynamic drag and the formation of large temperature gradients across the external structural parts of their airframe. To protect the vehicles, high‐infrared emissivity coatings that can radiate a large amount of heat into outer space are in demand. In this work, we describe the development and characterization of high emissivity ceramic coatings formed on a TC4 alloy surface by micro‐arc oxidation. We evaluate, in particular, the influence of NiSO4 concentration on current‐time response, the thickness, surface roughness, morphologies, bonding strength, and emissivity of these coatings. The results indicate that by increasing the NiSO4 concentration in electrolytes, the thickness and surface roughness of the coatings increase. The bonding strength becomes smaller with increasing concentration of NiSO4, but is still maintains a value higher 30 MPa. The coatings possess good thermal shock resistance after being subjected to severe thermal shocks for 50 cycles, and no peeling of the coating is observed. A higher concentration of NiSO4 in electrolytes also leads to an increasing percentage of the nickel components in the coating to form a NiO phase, which enhances the emissivity of the coatings in the wavelength range of 3‐8 μm. [ABSTRACT FROM AUTHOR]

This work presents an investigation on the damage and high-speed impact deformation mechanisms at elevated temperatures in honeycomb sandwich panels made from PM1000 and PM2000 alloys. The impact temperatures ranged from 22 °C to 866 °C. The investigation was performed experimentally using a custom-made gas gun rig, and by using Finite Element and developing a phenomenological analytical model to predict the residual velocity and ballistic limit equations for the case in which the diameter of the projectile is close or smaller to the honeycomb cell length. The sizes of the holes have been also evaluated by carrying out numerical thermal loading simulations on honeycomb sandwich specimen models impacted at high speed. The predictions provided by the Finite Elements and the analytical model give a good agreement with the results from the experimental tests. The hole diameters for the two idealized normal impact cases, in which the projectile hits the cell core and at the triple-wall intersection of the core, were also presented as a function of the projectile diameter and velocity in this paper. [ABSTRACT FROM AUTHOR]

This paper describes the vibroacoustic behavior of sandwich panels with a novel core topology made from 2-dimensionally gradient auxetic hexagonal honeycombs. The 2D gradient core enables a tailoring of localized mechanical properties of the sandwich structure in different regions of the panel. A homogenized finite element modeling has been used to initially determine the mechanical properties of the structures. The natural frequencies and the radiated sound power level of the sandwich plate with the homogenized properties have been calculated and verified with those obtained from a full-scale detailed model of the sandwich structure. The geometry of the 2-dimensionally gradient auxetic core has been then optimized using two different techniques in order to minimize the radiated sound power level over the frequency range of 0 to 200 Hz. The optimized design of the 2-D gradient core shows a remarkable reduction of the radiated sound power level for the sandwich structure when taking into account the mass of the panels. The results of this study provide new insights about the vibroacoustic behavior of hexagonal auxetic sandwich structures with complex core geometry. [ABSTRACT FROM AUTHOR]

We describe the in-plane compressive performance of a new type of hierarchical cellular structure created by replacing cell walls in regular honeycombs with triangular lattice configurations. The fabrication of this relatively complex material architecture with size features spanning from micrometer to centimeter is facilitated by the availability of commercial 3D printers. We apply to these hierarchical honeycombs a thermal treatment that facilitates the shape preservation and structural integrity of the structures under large compressive loading. The proposed hierarchical honeycombs exhibit a progressive failure mode, along with improved stiffness and energy absorption under uniaxial compression. High energy dissipation and shape integrity at large imposed strains (up to 60%) have also been observed in these hierarchical honeycombs under cyclic loading. Experimental and numerical studies suggest that these anomalous mechanical behaviors are attributed to the introduction of a structural hierarchy, intrinsically controlled by the cell wall slenderness of the triangular lattice and by the shape memory effect induced by the thermal and mechanical compressive treatment. [ABSTRACT FROM AUTHOR]

We describe the out-of-plane bending of kerf chiral fractal lattices metamaterials by using a combination of theoretical models, full-scale finite elements and experimental tests representing the flexural behaviour of metamaterial beams under three-point bending. Good agreement is observed between the three sets of results. Parametric analyses show a linear log-log relation between bending modulus and aspect ratios of the unit cells, which are indicative of the fractal nature of the metamaterial. The ratio between the bending and in-plane tensile moduli of these chiral fractal metamaterials ranges between ∼ 5 and ∼ 34 and is linearly proportional to the square of the ratio between length and width of the ribs of the chiral unit cells at different fractal orders. These properties suggest that the class of chiral fractal lattice metamaterials offer metacompliance properties between the flexural and in-plane stretching behaviours, which can be tailored by the adoption of the fractal scales. [ABSTRACT FROM AUTHOR]

In rural, arid, and desert areas such as in southern Algeria, constructions are generally based on the use of raw earth due to its availability, abundance, and low price. In addition, raw earth-based constructions require continuous repairs and restorations. Therefore, this work aims to develop a new eco-friendly, low-cost, and sustainable composite, which is adapted to the local climate and meets the structural requirements of earthen constructions. The new composite blocks are made from compressed raw earth and reinforced with date palm stems (DPS), moistened, and then statically compacted. The use of DPS is part of the recovery process of date palm waste that can be used as reinforcement in blocks and can also lead to the improvement of the mechanical and thermal performance. The chemical and mineralogical composition of the raw earth is first determined by X-ray fluorescence and X-ray diffraction, while its physical, chemical and mechanical properties are also determined using different international standards. Two varieties of DPS, namely the Teggaza and Telemso ones are tested under tensile loading, where the latter shows better mechanical properties compared to classical reinforcements in compressed earth blocks (CEB). Thirty reinforced CEB formulations have been here developed, with different weight content of DPS fibres (0.5, 1, 1.5 and 2 wt%), length (1, 2 and 3 cm), morphology (smooth, rough, and mixed) and DPS with four types of treatments (immersion, boiling, autoclaving and hornification). This work also provides an analysis of the mechanical characteristics of the composite blocks by highlighting the influence of the different parameters (i.e., percentage, length, morphology, and treatment of the DPS) on the bending and compressive strengths after drying for 7 and 28 days. [ABSTRACT FROM AUTHOR]

We propose in this paper analytical and numerical models that describe the in-plane uniaxial elastic properties (Young's moduli and Poisson's ratios) of a honeycomb structure with curved walls. We perform a parametric analysis of the mechanical performance of this honeycomb also by taking into account the different types of deformations acting inside the cell walls. The curved wall honeycomb possesses higher magnitudes of the Poisson's ratio ν12 in the auxetic configuration compared to classical center symmetric configuration with straight cell wall. The presence of the curvature also allows creating configurations with positive Poisson's ratio even for negative internal cell angles, and makes this honeycomb design attractive for mechanical tailoring. [ABSTRACT FROM AUTHOR]

Thin-walled tubular structures are commonly used in automotive and aerospace applications because of their high strength and lightweight characteristics. In this paper we propose a new bionic bi-tubular thin-walled structure (BBTS) inspired from the internal structure of the lady beetle elytron. Six types of BBTSs with different geometric parameters and same type of material were simulated under axial dynamic impact loading with a weight of 500 kg and a velocity of 10 m/s using nonlinear finite elements. The comparison between BBTSs with equal mass shows that the thickness of the inner wall and the cross-sectional configurations influence significantly the energy absorption of the structure. BBTSs show an optimized crashworthiness behavior when the inner wall thickness is between 1.6 and 2.0 mm. In addition, circular and octangular BBTSs show improved absorption characteristics when the inner wall thickness is 2.0 mm. We also evaluate the energy absorption of periodically distributed BBTS against cellular configuration with irregular topology. The energy absorption characteristic of BBTS with regular distribution is better than that of BBTS with irregular distribution, which indicates that the optimized regular structure has an improved mechanical performance to the original bionic topology. [ABSTRACT FROM AUTHOR]

This work describes the development of a sustainable and low-cost sandwich composite structure made from aluminium skins and bonded to a tubular core with epoxy resin. The core is made from disposed plastic bottle caps. An analysis of variance (ANOVA) has been performed to determine the significance of the orientation of the bottle caps in the core, the use and type of adhesive over the bulk density and the mechanical properties of the sandwich panels. The results show that a core topology made from an alternated orientation of the bottle caps provides an enhancement of the resistance in the face skins and the core. The use of the epoxy adhesive between adjacent bottle caps also gives an increase of the maximum resistance of the panel. [ABSTRACT FROM AUTHOR]

This study aims to assess the morphology and properties of fibers extracted from a wild natural plant largely available in Algeria known as Juncus effusus L. (JE). The morphology and diameter of the fiber bundles extracted from the stem of the JE plant were characterized by optical and scanning electron microscopy. The functional groups of the extracted lignocellulosic JE fibers were studied by FTIR, their thermal degradation behavior was investigated by TGA and their crystallinity was determined using X-ray diffraction technique. In addition, mechanical characterization was carried out using tensile tests on the lignocellulosic fiber in order to evaluate their strength, strain at break and Young's modulus. In view of the dispersion in the obtained experimental results, the latter were analyzed using the Weibull statistical laws with two and three parameters. [ABSTRACT FROM AUTHOR]

Fibre metal laminates (FMLs) have been widely used to manufacture airframe components. This work describes novel sisal fibre reinforced aluminium laminates (SiRALs) that have been prepared by cold pressing techniques and tested under tensile, flexural and impact loading. The pristine sisal fabric and the sisal fibre reinforced composites (SFRCs) were also tested to understand the difference in mechanical performance of the sisal fibre metal laminates. The SiRALs achieved not only the highest modulus and strength, but also the highest specific properties. The mean specific tensile strength and modulus of the SIRALs reached increases of 132% and 267%, respectively, when compared to the sisal fibre reinforced composites (SFRCs). Moreover, the mean specific flexural strength and modulus of the SiRALs were significantly higher than SFRCs, revealing increases of 430% and 973%, respectively. A delamination fracture mode was noted for SiRALs under bending testing. The SiRALs can be considered promising and sustainable composite materials for structural and multifunctional applications. [ABSTRACT FROM AUTHOR]

Hybrid Glass Fibre Reinforced Composites (HGRFCs) made with unidirectional glass fibres and silica or cement microparticles inclusions were investigated in order to improve their performance under flexural and impact loadings. Two full factorial designs were conducted to evaluate (i) the effect of the particle weight fraction on the compressive modulus of epoxy polymer (2 1 3 1 ) and (ii) the effect of the number of layers and type of particle (3 2 ) on the apparent density, flexural modulus and strength of HGFRCs. Composites with higher flexural properties were evaluated under impact loading via one-way analysis. TGA and FTIR analyses were used to verify the effect of ceramic particles within the polymeric phase. A microstructural analysis (SEM) was performed to verify the fracture mode and better assess the mechanical performance of HGFRCs. [ABSTRACT FROM AUTHOR]

This paper describes an experimental and signal processing technique to perform high temperature tests on superalloy (INCONEL) and carbon/carbon structures using silica-based chemical composition gratings (CCGs). The results obtained from applying this technique at 940°C in superalloys and 950°C for carbon/carbon (C/C) composites are benchmarked against data obtained from four different methods. The results show that the wavelength responses of the CCGs bonded on the superalloy and on the C/C plate increase nonlinearly with increasing temperatures. The temperature-dependent strain transfer coefficients recorded during the superalloy tests show quite stable results below 600 °C and tend to slightly decrease thereafter. The values of the strain transfer coefficients below 1000 °C are significantly affected by the thermal expansion coefficient of the substrate material and the interface. We demonstrate that the strain transfer coefficient calculation method used in this paper is not suitable for low and/or negative expansion material. The results of the relative errors show that the CCGs-F method based on the quadratic dependence of the wavelength shift versus the temperature appears to be the best to estimate the mechanical strains within the interval of temperatures considered and the measurement accuracy. The relative errors measured between 200 °C and 1000 °C are less than 5%. [ABSTRACT FROM AUTHOR]

This work describes a Finite Element sequential multiscale technique to evaluate hybrid composites made of fibres and particles. The representative volume element (RVE) makes use of a 3D Finite Element (FE) models constrained with different boundary conditions. The macroscale represents the geometry of ASTM specimens manufactured for experimental testing. A User Material subroutine (UMAT) reproduces the behaviour of the micromechanical properties at a larger scale. Carbon fibre-reinforced polymer (CFRP) and silica particle reinforced CFRP (CFSPRP) are experimentally evaluated under tension, compression and in-plane shear. Hand layup and vacuum bag techniques are used to produce those composites. The hybrid configuration considers 9 wt% of particles for the total mass of the matrix. Numerical results show the accuracy provided by the proposed multiscale modelling technique in predicting the elastic and inelastic responses versus the experimental results. [ABSTRACT FROM AUTHOR]

The deformation and fracture mechanisms of penta-graphene under different loading conditions are still unclear and not thoroughly investigated. Hereby, the mechanical and transition/failure deformation properties of penta-graphene are investigated by using free standing nanoindentation techniques simulated via molecular dynamics. The indentation behaviors of penta-graphene under spherical and cylindrical indenters are compared and analyzed parametrically by considering the effects of the spherical/cylindrical indenter size, the loading rate and temperature. The results show that penta-graphene under spherical and cylindrical indentation exhibits unusual plastic deformation characteristics, which are consistent with those previously observed under uniaxial tensile and shear loading. The plastic deformation is originated from the pentagon-to-polygon structural transformation occurring at large indentation depths. The force at failure of the penta-graphene under spherical indenter is significantly lower than the one observed under cylindrical indenter; this is due to the small interaction area and high stress concentration caused by spherical indenter. We also identify the indentation parameters to accurately predict the mechanical parameters of penta-graphene using spherical or cylindrical indenters, and how these parameters influence the nanoindentation results. It is found that under both spherical and cylindrical indenter the Young's modulus of the penta-graphene is not sensitive to the loading rate, but generally decreases with the increasing temperature. [Display omitted] • The mechanics of PG under different indenters are examined using nanoindentation. • PG under indentation loading exhibits unusual plastic deformation characteristics. • The mechanism of plastic deformation is originated from structural transformation. • The indentation parameters to predict the mechanical parameters are identified. [ABSTRACT FROM AUTHOR]

The appreciation of how conventional and fossil-based materials could be harmful to our planet is growing, especially when considering single-use and non-biodegradable plastics manufactured from fossil fuels. Accordingly, tackling climate change and plastic waste pollution entails a more responsible approach to sourcing raw materials and the adoption of less destructive end-of-life pathways. Livestock animals, in particular ruminants, process plant matter using a suite of mechanical, chemical and biological mechanisms through the act of digestion. The manure from these "living bioreactors" is ubiquitous and offers a largely untapped source of lignocellulosic biomass for the development of bio-based and biodegradable materials. In this review, we assess recent studies made into manure-based cellulose materials in terms of their material characteristics and implications for sustainability. Despite the surprisingly diverse body of research, it is apparent that progress towards the commercialisation of manure-derived cellulose materials is hindered by a lack of truly sustainable options and robust data to assess the performance against conventional materials alternatives. Nanocellulose, a natural biopolymer, has been successfully produced by living bioreactors and is presented as a candidate for future developments. Life cycle assessments from non-wood sources are however minimal, but there are some initial indications that manure-derived nanocellulose would offer environmental benefits over traditional wood-derived sources. [Display omitted] • Recent research into the development of high-value manure-derived materials was reviewed. • Developments can be divided into crude materials, composites and purified derivatives. • Methods to ensure good adhesion between manure materials and surrounding matrix were a key feature within composites. • Several gaps in the existing literature present potential barriers to commercial uptake. • Nanocellulose is proposed as a prospective sustainable material of the future. [ABSTRACT FROM AUTHOR]

The design of impact-resistant composite laminates could be inspired by a biologically helicoidal architecture where a series of thin unidirectional fibre laminas are stacked one by one, with the orientation of each fibre layer rotating sequentially by a near-constant angle. The results of low-velocity/face-on impact show that the excessive diffusion of damage inside the helicoidal configurations poses a potential threat to the structural integrity of size-limited laminates, even though the fibre failure is suppressed (which tends to occur in the Cross-Ply controls, resulting in lower contact force). Here, we propose a cross-helicoidal design strategy for the fabrication of high-performance helicoidal composites with variable rotation angles. By adjusting the relative position of the oriented fibre sheets, this cross-helicoidal architecture changes the out-of-plane stiffness of the original helicoidal configuration, resulting in a rather different impact response. Both experimental data and numerical simulations confirm that the introduction of this cross-helicoidal design significantly improved the impact resistance of laminates, with larger impact peak forces and much smaller projected damage area. [ABSTRACT FROM AUTHOR]