Tommaso Magrini

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Magrini

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Tommaso

ORCID

0000-0002-6075-7625

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Publications 1 - 8 of 8

Tough and Transparent Nacre-like Functional Composites
Magrini, Tommaso (2021)
Bioinspired bulk composites present an internal structure that is built to replicate selected features from biological composites, such as high strength and fracture toughness. Strength and toughness play a key role in most structural applications, as they provide mechanical stability and reliability. Although research efforts have been mostly focused on the optimization of the mechanical performance of synthetic structural composites, the hallmark of biological composites is their ultimate ability to combine within the same material additional functionalities, such as color, self-healing, sensing, or shape responsiveness. However, the implementation of sensing- or optical properties in today’s composites without sacrificing strength and toughness remains challenging. Rethinking materials processing to combine multiple functionalities within a single bioinspired composite was one of the major drives of my doctoral studies. In this thesis, we have developed biologically inspired composite materials that replicate the microstructure of mother-of-pearl, also known as nacre, and that combines optical transparency, strength, fracture toughness and sensing capabilities. First, a simple and scalable process is developed to fabricate transparent nacre-like composites that feature mineral bridges at the nanoscale. Commercially available glass platelets with a thickness of 1 μm and a large aspect ratio of approximately ~300 are shaped into an interconnected scaffold that is then infiltrated with an organic matrix with the same refractive index as glass. The mechanical properties of such bioinspired composites are assessed by quasi- static flexural tests and fracture experiments. Compared to commercially available glass, these composites display a ~3 fold higher fracture toughness. To investigate more in depth how the toughening mechanisms operate and act in synergy during the fracture of the composites, we have conducted a set of in situ fracture experiments on a wedge splitting tester (WST). Although local crack deflection clearly takes place during fracture, our analysis has indicated that polymer ligament bridging is the primary responsible for the increased toughness values. Building on the knowledge gained on these new composites, we have assembled transparent nacre-like composite layers into a hierarchical multi-layered bioinspired composite that features alternating stiff nacre-mimetic layers and soft polymer layers. By synthesizing polymer matrices with different mechanical properties, the role of the polymer phase on the fracture process was thoroughly investigated. With this work, we have demonstrated that crack deflection and branching is not sufficient to increase the fracture toughness of the composite. A strong and tough polymer phase is also required to effectively dissipate energy during fracture. The resistance against fracture of our multi-layered composites is granted by local plastic deformation at early fracture stages and large-scale crack bridging at late stages of the fracture process. Finally, we have harnessed the transparency of the hierarchical composites to implement damage-sensing functionalities in a strong and tough structural composite. This is achieved by introducing mechanochromic crosslinkers in the polymer network that is used as organic phase of the bioinspired material. Importantly, the molecular nature of the mechanosensors provided rich local stress information without compromising the mechanical properties of the composite. By developing a synthetic composite with data- and damage-reporting capabilities, we were able to visualize the fracture process, quantify the toughness and detection early damage in complex layered architectures. The bulk bioinspired composites developed in this thesis constitute a promising alternative to retro-illuminated transparent displays, which often suffer from brittle fractures and poor damage tolerance. Furthermore, these new composites offer a powerful material platform to study the development of fracture in hierarchical architectures and represent a standalone new class of structural composites that can report, quantify and pre-emptively detect damages.
Hierarchical Porous Monoliths of Steel with Self-Reinforcing Adaptive Properties
Carpenter, Julia A.; Saraw, Zoubeir; Schwegler, Alain; et al. (2023)
Advanced Materials
Porous structures offer an attractive approach to reduce the amount of natural resources used while maintaining relatively high mechanical efficiency. However, for some applications the drop in mechanical properties resulting from the introduction of porosity is too high, which has limited the broader utilization of porous materials in industry. Here, it is shown that steel monoliths can be designed to display high mechanical efficiency and reversible self-reinforcing properties when made with porous architectures with up to three hierarchical levels. Ultralight steel structures that can float on water and autonomously adapt their stiffness are manufactured by the thermal reduction and sintering of 3D printed foam templates. Using distinct mechanical testing techniques, image analysis, and finite element simulations, the mechanisms leading to the high mechanical efficiency and self-stiffening ability of the hierarchical porous monoliths are studied. The design and fabrication of mechanically stable porous monoliths using iron as a widely available natural resource is expected to contribute to the future development of functional materials with a more sustainable footprint.
Fracture of hierarchical multi-layered bioinspired composites
Magrini, Tommaso; Senol Güngör, Ayca; Style, Robert; et al. (2022)
Journal of the Mechanics and Physics of Solids
Lightweight composites have revolutionized the sector of aircrafts and will continue to play a major role in future energy-efficient transportation systems. However, the design of composites featuring high strength and high fracture toughness remains challenging due to the usual trade-off between these properties in synthetic materials. Inspired by the strong and tough hierarchical architecture of mollusk shells, we create tough composites by combining soft polymer layers with alternating, nacre-like layers that are infiltrated with the same polymer. Here, we study the fracture behavior and the toughening mechanisms underlying the high crack growth resistance of these hierarchical composites. Polymer layers with different stiffness and yield strength were designed in order to evaluate the effect of plastic deformation and bridging of the polymer phase on the early and late stages of the fracture process. Controlled fracture experiments allowed us to visualize the interactions of a propagating crack with the hierarchical architecture and to quantify the resistance of the polymer layer against early-stage fracture. Our findings provide new insights into the interplay of multiscale toughening mechanisms in hierarchical bioinspired architectures and offer guidelines for the design and manufacturing of strong and tough lightweight composites.
Transparent and tough bulk composites inspired by nacre
Magrini, Tommaso; Bouville, Florian; Lauria, Alessandro; et al. (2019)
Nature Communications
Materials combining optical transparency and mechanical strength are highly demanded for electronic displays, structural windows and in the arts, but the oxide-based glasses currently used in most of these applications suffer from brittle fracture and low crack tolerance. We report a simple approach to fabricate bulk transparent materials with a nacre-like architecture that can effectively arrest the propagation of cracks during fracture. Mechanical characterization shows that our glass-based composites exceed up to a factor of 3 the fracture toughness of common glasses, while keeping flexural strengths comparable to transparent polymers, silica- and soda-lime glasses. Due to the presence of stiff reinforcing platelets, the hardness of the obtained composites is an order of magnitude higher than that of transparent polymers. By implementing biological design principles into glass-based materials at the microscale, our approach opens a promising new avenue for the manufacturing of structural materials combining antagonistic functional properties.
Fabrication of Three-Dimensional Polymer-Brush Gradients within Elastomeric Supports by Cu-0-Mediated Surface-Initiated ATRP
Faggion Albers, Rebecca; Magrini, Tommaso; Romio, Matteo; et al. (2021)
ACS Macro Letters
Cu-0-mediated surface-initiated ATRP (Cu-0 SI-ATRP) emerges as a versatile, oxygen-tolerant process to functionalize three-dimensional (3D), microporous supports forming single and multiple polymer-brush gradients with a fully tunable composition. When polymerization mixtures are dispensed on a Cu-0-coated plate, this acts as oxygen scavenger and source of active catalyst. In the presence of an ATRP initiator-bearing microporous elastomer placed in contact with the metallic plate, the reaction solution infiltrates by capillarity through the support, simultaneously triggering the controlled growth of polymer brushes. The polymer grafting process proceeds with kinetics that are determined by the progressive infiltration of the reaction solution within the microporous support and by the continuous diffusion of catalyst regenerated at the Cu-0 surface. The combination of these effects enables the accessible generation of 3D polymer-brush gradients extending across the microporous scaffolds used as supports, finally providing materials with a continuous variation of interfacial composition and properties. © 2021 American Chemical Society
Complex Materials: The Tough Life of Bone
Magrini, Tommaso; Libanori, Rafael; Kan, Anton; et al. (2021)
Revista Brasileira de Ensino de Física
Bone was a crucial biological material for the evolution of large terrestrial organisms and is today essential for most of our daily activities and well-being. From an engineering perspective, this living material features highly desirable properties for modern load-bearing structures. It is made of abundant and environmental-friendly building blocks, which are combined into a tough and durable structure that can continuously modify itself to adapt to changes in the mechanical load imposed by the surroundings. In this review article, we compile and discuss scientific findings that allow us to understand bone as a complex system with properties that emerge from cell-mediated interactions of molecules and particles at multiple length scales. Analogous to other complex systems, such interactions lead to self-organization, hierarchical structures and adaptive behavior without the need of a central controlling unit. A rich range of physical, chemical and biological phenomena provide a framework for information to be generated and processed in this complex system. Understanding the interplay between such underlying phenomena and their emerging properties should help the diagnosis and treatment of bone-related medical conditions and might provide guidelines for the future development of more sustainable materials and engineering structures.
Tough Bioinspired Composites That Self-Report Damage
Magrini, Tommaso; Kiebala, Derek; Grimm, Dominique; et al. (2021)
ACS Applied Materials & Interfaces
The increasing use of lightweight composite materials in structural applications requires the development of new damage monitoring technologies to ensure their safe use and prevent accidents. Although several molecular strategies have been proposed to report damage in polymers through mechanochromic responses, these approaches have not yet been translated into lightweight bioinspired composites for load-bearing applications. Here, we report on the development of bioinspired laminates of alternating polymer and nacre-like layers that combine optical translucency, high fracture toughness, and damage-reporting capabilities. The composites signal damage via a fluorescence color change that arises from the force activation of mechanophore molecules embedded in the material’s polymer phase. A quantitative correlation between the applied strain and the fluorescence intensity was successfully established. We demonstrate that optical imaging of mechanically loaded composites allows for the localized detection of damage prior to fracture. This fluorescence-based self-reporting mechanism offers a promising approach for the early detection of damage in lightweight structural composites and can serve as a useful tool for the analysis of fracture processes in bulk transparent materials. © 2021 American Chemical Society
Transparent materials with stiff and tough hierarchical structures
Magrini, Tommaso; Bouville, Florian; Studart, André R. (2021)
Open Ceramics

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Tommaso Magrini

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