Fabrizio Scarpa

• Laurea in Ingegneria Aeronautica
• Professor (Full) at University of Bristol

A scalable mechanical metamaterial simultaneously displaying negative stiffness and negative Poisson's ratio responses is presented. Interlocking hexagonal subunit assemblies containing 3 alternative embedded negative stiffness (NS) element types display Poisson's ratio values of -1 and NS values over two orders of magnitude (-1.4 N mm(-1) to -160...

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 modelled using...

The proverbial "nine lives" of cats are attributed to the capacity of the felines to withstand jumps and falls from a high-rise without being fatally wounded, and this is due in large part to their impact-resistant paw pads. The pads possess a complex architecture of multiscale collagen fiber networks and adipose mass chambers. We propose in this p...

Humidity responsive materials are increasingly attracting significant interest for soft robotics and deployable structures. Their shape-changing behavior is based on differential hygroscopic characteristics of the single components of their microscopic architecture. Although existing moisture-induced materials achieve morphing in various humidity c...

Conventional vibration energy harvesters based on two-dimensional planar layouts have limited harvesting capacities due to narrow frequency bandwidth and because their vibratory motion is mainly restricted to one plane. Three-dimensional architected structures and advanced materials with multifunctional properties are being developed in a broad ran...

This Roadmap surveys the diversity of different approaches for characterising, modelling and designing metamaterials. It contains articles covering the wide range of physical settings in which metamaterials have been realised, from acoustics and electromagnetics to water waves and mechanical systems. In doing so, we highlight synergies between the...

Hygromorphic materials and composites adjust their shape and curvature in response to changes in relative humidity, similar to the pinecone scales existing in nature. This work introduces a new class of poligromorphic materials‐composites that adapt across various environments, including water, humidity, and hydrocarbons. Composed of carbon fibers...

The work presents a deep learning-driven approach integrating forward and reverse design to generate families of mechanical metamaterials fusing different shapes and functionalities. A deep learning model of a double neural network integrates forward and reverse design provides a novel strategy for general metamaterial design by generating and opti...

This paper investigates the synergistic effects of heat treatment degrees, chemical or mechanical extraction methods, and the presence of bamboo nodes on the mechanical properties of bamboo fiber bundles. Chemically extracted fiber bundles exhibited higher tensile strength from 248.9 to 530.9 MPa, compared with mechanically extracted fiber bundles...

Modular structures are essential for enhancing construction efficiency, reducing costs, and providing flexibility in design across various industries. Sandwich panels, composed of stiff outer skins and lightweight cores, are widely recognized for their high strength-to-weight ratios, durability, and adaptability. Among core designs, arched corrugat...

Roots can mechanically reinforce soils against landslides, but the impact of their typically random and complex distribution on this reinforcement is not well understood. Here, using a modelling approach based on homogenization theory, we aim to assess the effect of the randomness and complexity of root spatial distribution in soils on the mechanic...

Metamaterials and metastructures are traditionally made using fossil-based components. We describe here an eco-friendly and sustainable alternative to build metastructures with load-bearing characteristics by using a novel and modular trussed cell concept from natural composite rods derived from the giant bamboo ( Dendrocalamus asper ) and bi-phasi...

The review focuses on architected acoustic metamaterials to manipulate airborne sound waves, with only limited discussions on elastic metamaterials related to solid media. We review the design of acoustic metamaterials and the physical mechanisms underpinning their performance and related manufacturing methodologies, while also examining potential...

Biological structures provide inspiration for developing advanced materials from sustainable resources, enabling passive structural morphing. Despite an increasing interest for parsimony‐oriented innovation, sustainable shape‐changing materials based on renewable resources remain underexplored. In this work, the architecture of a single plant fiber...

We have developed hydrogel systems with tunable porosity through dialysis casting by varying alginate and poloxamer compositions from 0% to 10%. These gels feature diverse porosity topologies, yielding loss factors between 16% and 29% in the 50 Hz to 300 Hz frequency range. The dynamic modulus shows a remarkable increase of over an order of magnitu...

The application of lignocellulosic fibers to reinforce mortars with cementitious matrices was investigated for possible use in non-structural applications. A Box-Behnken design L29 (BBDL29) experimental design, using the response surface method (RSM), was used to obtain the combination that maximizes the bending stress and modulus. Four input param...

We have developed hydrogel systems with tunable porosity through dialysis casting by varying alginate and poloxamer compositions from 0% to 10%. These gels feature diverse porosity topologies, yielding loss factors between 16% and 29% in the 50 Hz to 300 Hz frequency range. The dynamic modulus shows a remarkable increase of over an order of magnitu...

Uniaxial thermoforming compression is a promising technique for producing Negative Poisson's Ratio (NPR) open-cell foams. It allows for faster, easier, and more scalable production. The sustainability credentials of this method can be further improved by exploiting bio-based (i.e., from vegetable oils) open-cell polyurethane foams to generate NPR p...

Granular hydrogels, composed of densely packed microgels, are an emerging class of injectable microporous scaffolds that provide interstitial porosity for endogenous cell recruitment and tissue repair. However, weak bonding interactions between constituent microgels compromises the mechanical integrity of these biomaterials, limiting their scope an...

Glued laminated bamboo (glubam), a product of bamboo lamination, presents a distinctive combination of eco-friendliness and mechanical strength. This study delves into the quasi-static and dynamic compression behaviour of glubam, examining the influence of key factors such as moisture content and carbonization. The experiment involved one control g...

Rigid polyurethane foams (RPUFs) are widely used in impact protection applications due to their tunable mechanical properties. Recently, RPUFs derived from bio-based sources such as castor oil have been investigated as a greener and more sustainable alternative to replace fossil-based polyurethane foams. It is thus important to understand the mecha...

Environmental concerns surrounding petrochemical-based materials are constantly increasing and they are pushing the industry to find renewable sources and sustainable solutions. Recent years have also witnessed a focus on the development of multifunctional and metamaterials such as auxetic structures. This work describes the manufacturing of castor...

Environmental concerns surrounding petrochemical-based materials are constantly increasing and they are pushing the industry to find renewable sources and sustainable solutions. Recent years have also witnessed a focus on the development of multifunctional and metamaterials such as auxetic structures. This work describes the manufacturing of castor...

This paper describes the extrusion pressure’s effect on composite hydrogel inks’ filaments subjected to three point bending collapse tests. The composite considered in this work consists of an alginate-poloxamer hydrogel reinforced with flax fibres. Increased extrusion pressure resulted in more asymmetrical filaments between the support pillars. Fu...

Developing sustainable composites for engineering applications is essential for minimizing environmental impacts and ensuring the long‐term viability of infrastructure and technological advancements. In this context, this work focuses on the manufacture and evaluation of the structural integrity of a sandwich structure composed of aluminum faces an...

Biological structures combine passive shape‐changing with force generation through intricate composite architectures. Natural fibers, with their tubular‐like structures and responsive components, have inspired the design of pneumatic tubular soft composite actuators. However, no development of passive structural actuation is available despite the r...

Honeycombs are commonly used as core materials in sandwich panels, and the core geometry significantly impacts the bending behaviour of these structures. Understanding how core characteristics influence the mechanical properties of sandwich panels is essential. The comparison between different honeycomb sandwich panel configurations is quite comple...

We study the shear behavior of pristine and uniaxially thermoformed auxetic foams using three different shear testing techniques and finite element simulations. A novel simple shear test rig with sliding lateral supports was developed and compared to fixed simple shear and diagonal pure shear rigs. The three rigs yield similar results at shear stra...

Shear-stiffening gels are flexible materials whose modulus is significantly increased upon rapid impact. They have applications in protective and other devices but are generally limited by difficult processability and poor shape retention. Here we demonstrate a simple and scalable process for making elastic shear-stiffening composites with locally...

In this work, a flexible polyurethane (PU) foam/polymer/clay (PUF/PAASep) composite is prepared via a simple dip-coating method. The composite exhibits excellent damping properties under quasi-static compression, vibration transmissibility, and impact resistance. For the composite preparation, sepiolite (Sep) dispersion in a polyacrylic acid (PAA)...

Hydrogels find widespread applications in biomedicine because of their outstanding biocompatibility, biodegradability, and tunable material properties. Hydrogels can be chemically functionalized or reinforced to respond to physical or chemical stimulation, which opens up new possibilities in the emerging field of intelligent bioelectronics. Here, t...

This paper proposes a multi-objective optimization method for the optimal balancing of flexible rotors without using trial weights to overcome the drawbacks of repeatedly starting and stopping and applying trial weight during the balancing process of multidisc flexible rotors. Finite elements are first used to develop a dynamic model of the flexibl...

To automate the approach of assessing the health and efficacy of large structural systems globally through structural health monitoring systems, a vast network of sensors that must be mounted throughout the entire structure and connected to a continuous power supply is necessary. Clusters of wires need to be placed throughout the structures to supp...

Shape-shifting between multiple stable deformation states offers attractive pathways to design adaptive structures. Ideas have been conceptualised in diverse fields, including soft robotics and aerospace engineering. The success of shape-shifting relies on overcoming the energy barrier separating adjacent stable configurations, which necessitates e...

Stress concentrations pose a significant challenge in designing and optimizing composite components, often resulting in structural alterations and crack formation. This study delves into a detailed numerical and analytical analysis of stress concentration factors in composite materials, with a specific focus on the influence of negative Poisson's r...

This work describes the devulcanization of ground tire rubber (GTR) with particle sizes ranging from 0.6 to 0.122 mm using a non-toxic, biodegradable, and biocompatible deep eutectic solvent (DES) based on choline chloride and urea. In addition to reducing the environmental impact of the process, other goals of this study were to minimize time and...

An innovative two dimensional auxetic metamaterial was designed by mirroring a parallelogram with two parallel ligaments along the horizontal and vertical directions. The architecture of the metamaterial is based on the adoption of a structural chiral deformation mechanism induced by the rotation of the connecting joint of the parallel ligaments. A...

Correction for ‘Flax fibre reinforced alginate poloxamer hydrogel: assessment of mechanical and 4D printing potential’ by Charles de Kergariou et al. , Soft Matter , 2024, 20 , 4021–4034, https://doi.org/10.1039/D4SM00135D.

The mechanical and printing performance of a new biomaterial, flax fibre-reinforced alginate-poloxamer based hydrogel, for load-bearing and 4D printing biomedical applications is described in this study. The-self suspendable ability of the material was evaluated by optimising the printing parameters and conducting a collapse test. 1% of the flax fi...

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 alternati...

Understanding the limits of the design space is a key aspect in optimising complex hierarchical structures and is vital for exploring and designing novel Metamaterials. Simultaneously, abundant data (mostly text, images, and location) aggregated by multinational corporations accelerated the development of machine learning and artificial intelligenc...

Hygromorph BioComposites (HBC) exhibit shape-changing actuated by a moisture content (MC) variation due to their bilayered bioinspired architecture. However, their application in daily meteorologic variation is limited due to relative humidity (RH) and thermal couplings. This work aims to investigate the role of temperature variation on the shape c...

Despite the extensive research on renewable resources (RR) and their potential applications in composite materials and sandwich structures, there remains a significant dearth of life cycle assessment (LCA) studies that comprehensively evaluate the efficacy of RR in mitigating environmental impacts (EI). To bridge this gap, the present study aims to...

Sandwich panels composed of aluminium skins and egg-box-shaped cores made with natural fibre composites are tested in three-point bending and evaluated statistically and through failure analysis. The corrugated cores are assessed with filled bio-based foam. In order to produce these sandwich panels, preliminary investigations on natural fibre compo...

Hybrid composites are an advanced solution that offers multifunctional capabilities, including exceptional strength-to-weight ratios, vibrational damping and impact absorption. This work describes the damping capacity and flexural behaviour of a hybrid fibrous-particulate system composed of glass/carbon fabrics and three distinct micro-inclusions:...

This paper proposes a modified iterative learning control (MILC) periodical feedback-feedforward algorithm to reduce the vibration of a rotor caused by coupled unbalance and parallel misalignment. The control of the vibration of the rotor is provided by an active magnetic actuator (AMA). The iterative gain of the MILC algorithm here presented has a...

This paper illustrates the development of a novel sandwich panel for vibroacoustic applications by using novel materials as passive damping mechanisms. A flax-fibre composite is adopted for lattice core and skins. Carbon-nanotube reinforced viscoelastic inserts are embedded in critical locations within the lattice to further increase its vibration...

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 properti...

PU foams are versatile materials that find applications in a wide range of products, from upholstery to packaging and construction. These foams consist primarily of two components, polyol and prepolymer, and their concentrations play a crucial role in determining their physical and mechanical properties. A second-order mixture design approach is us...

Modular manufacturing is highly desirable due to its ability to quickly adapt to changing client demands and therefore its propensity to create high-margin products. However, this flexibility comes with the challenge of rapidly redesigning facility layouts when product demand or specifications change. Traditional Discrete Event Simulations (DES) ar...

This paper proposes a multi-objective optimization method for the optimal balancing of flexible rotors without using trial weights. Finite elements are first used to develop a dynamic model of the flexible rotor. An optimization method and an inverse identification approach are then used to minimize the objective function by considering constraints...

This study presents the first assessment of sustainable aluminium sandwich panels with an arched-core geometry. The arches are constructed from recycled aluminium obtained from drink container cans and bonded to aluminium skins using a polymer system. Through statistical analysis, the research aims to investigate the influence of the adhesive syste...

Classical approaches to enhance auxeticity quite often involve exploring or designing newer architectures. In this work, simple geometrical features at the member level are engineered to exploit non-classical nonlinearities and improve the auxetic behaviour. The structural elements of the auxetic unit cell are here represented by thin strip-like be...

Composite materials are used in a substantial number of products. Environmental concerns highlight the need for the inclusion of recovered waste in their formulation, thus reducing their carbon footprint. These solutions raise the need to confirm the mechanical characteristics of these materials, avoiding unwanted failures. In this work, the author...

Acoustic metamaterials are increasingly being considered as a viable technology for sound insulation. Fractal patterns constitute a potentially groundbreaking architecture for acoustic metamaterials. We describe in this work the behaviour of the transmission loss of Hilbert fractal metamaterials used for sound control purposes. The transmission los...

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...

This work describes the flexural behavior of biocomposites composed of a polyurethane matrix derived from castor oil plants and coir fibers. A statistical design is performed to identify the effects of fiber alkaline treatment and aging on the flexural modulus and strength of the composites. Physical tests and failure analyses are carried out to be...

Multistable tensegrity structures are able to switch between equilibrium configurations and maintain these states with no additional energy input; as a result, they have found applications in reconfigurable robotics and deployable structures. However, the actuation strategy for multistable tensegrity structures to transform from one stable state to...

This paper aims to present a hemp-based natural fibres composite value chain that could be implemented in biocomposite structures and replace synthetic fibres. Life cycle assessment (LCA) allows the assessment of the environmental footprint of the hemp fibre reinforcement value chain. This general case is complemented with two hemp fibre reinforcem...

Although hydrogen is one of the most abundant gases in the universe and having a major energyand ecological interest, at present it has not been sufficiently exploited, despite that it can be used in severalsectors such as the production of electrical energy which is now the global challenge of the 21st century,or in the means of land, sea and air...

In this work, the variational asymptotic method (VAM) based homogenization framework is used for the first time to determine the equivalent elastic stiffness tensor of auxetic materials. The proposed method allows the structural elements of the auxetic unit cell to naturally incorporate rotational degrees of freedom, without any ad-hoc assumptions....

Origami bellows are formed by folding flat sheets into closed cylindrical structures along predefined creases. As the bellows unfold, the volume of the origami structure will change significantly, offering potential for use as inflatable deployable structures. This paper presents a geometric study of the volume of multi-stable Miura-ori and Kreslin...

This work compares the behaviour between epoxy and novel bio-based castor oil matrix composites reinforced with glass and aramid fibres manufactured by vacuum infusion. A full factorial design is applied to statistically identify the effects of polymer and fibre-type factors on the physical, tensile, flexural, and impact properties of these composi...

This paper describes the derivation of a phenomenological model for shape memory alloys under the framework of classical plasticity theory. The proposed model combines the Souza constitutive approach with kinematic hardening; the model requires solving only one nonlinear equation rather than several nonlinear ones, therefore increasing the computat...

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...

Current applications of mass diffusion in composite structures with natural fibres reinforcements focus on the development of large thickness, balanced laminates, and long diffusion times. Hygromorph composites are, however, thin in thickness and possess slender shapes with unbalanced laminate designs, together with higher moisture diffusion speeds...