Periodic Reporting for period 1 - DIAGONAL (Ductility and Fracture Toughness analysis of functionally graded materials.)
Reporting period: 2023-03-01 to 2025-02-28
In this project, we aim to build an intercontinental and inter-multidisciplinary research network to unravel what is referred to as a pending challenge of Continuum Mechanics, Material Science, Aerospace Engineering and Civil Engineering: analysis and optimization and design of new functionally graded materials with unprecedented combinations of mechanical properties and functionalities, such as stiffness, strength, ductility, toughness, and formability, with minimal weight and cost. The rational solution to this problem is to adapt the local properties of different materials to fit specific requirements, by locating optimized compositions and architectures in appropriate regions, and generating multiple advantages within a single material to create improved global properties. The network is an international consortium composed by 10 research organizations, (4 European beneficiaries and 4 American, 1 Australian and 1 Brazilian partners) who will exchange and share skills and knowledge with the view to understand and optimize the ductile and toughness behavior of brittle (polymeric) and ductile (metallic) functionally graded materials. Breakthroughs in this field will allow functionally graded materials fabricated by additive manufacturing to replace traditional composites with sharp transition between dissimilar components commonly used in critical applications in construction of civil infrastructures and in aerospace, security and transportation industries, all sectors of crucial importance for the European economy and society. The staff members who participate in the project will be exposed to new research environments and develop new skills, thus contributing to their increased employability and supporting top-class research in Europe. The 10 organizations will further strengthen their knowledge base, and develop lasting collaborations. The credibility of the beneficiaries of the network to meet the ambitious scientific and training objectives of DIAGONAL is backed by 2 ERC grants and 3 MSCA networks (2 ITN and 1 RISE) that have been led by different members of the consortium.
Functionally graded materials (FGM) are a new class of advanced materials, very interesting for a wide range of engineering applications because they enable the design of different functional performances within a single part. The research in this area is still in nascent stage and new advances in graded materials are opening exciting new fields of applications, like aerospace, civil and construction. FGMs are defined as composite materials that consist of two or more material ingredients that are engineered to have a continuous spatial variation of material properties. These materials are characterized by gradual variation in structure and composition. With an optimized gradual transition, FGMs permit tailoring of material composition and derive maximum benefits offering great promise in applications for the aforementioned sectors. The use of these materials also poses several challenges, including mass production, minimal weight, the quality control of the graded area and cost, as well as enhancing production methods so that the components manufactured with grade properties are produced in a higher degree of accuracy.
DIAGONAL is the FIRST ATTEMPT EVER to develop a transcontinental, integral, and multidisciplinary approach to understand, and model FLOW and FRACTURE response of engineering FGMs which combine high specific mechanical properties with design flexibility, thus showing particularly high weight-reduction potential.
The project is expected to make an impact on several levels: scientifically, by advancing modeling and material characterization; industrially, by enabling new processes and improved materials; economically, by contributing to European competitiveness; environmentally, by supporting more efficient use of materials and lower emissions; and socially, by helping train skilled researchers and fostering long-term international collaboration. Overall, DIAGONAL aims to contribute to more efficient, adaptable, and sustainable material design that meets current and future engineering and societal needs.
Functionally graded materials (FGM) are a new class of advanced materials, very interesting for a wide range of engineering applications because they enable the design of different functional performances within a single part. The research in this area is still in nascent stage and new advances in graded materials are opening exciting new fields of applications, like aerospace, civil and construction. FGMs are defined as composite materials that consist of two or more material ingredients that are engineered to have a continuous spatial variation of material properties. These materials are characterized by gradual variation in structure and composition. With an optimized gradual transition, FGMs permit tailoring of material composition and derive maximum benefits offering great promise in applications for the aforementioned sectors. The use of these materials also poses several challenges, including mass production, minimal weight, the quality control of the graded area and cost, as well as enhancing production methods so that the components manufactured with grade properties are produced in a higher degree of accuracy.
DIAGONAL is the FIRST ATTEMPT EVER to develop a transcontinental, integral, and multidisciplinary approach to understand, and model FLOW and FRACTURE response of engineering FGMs which combine high specific mechanical properties with design flexibility, thus showing particularly high weight-reduction potential.
The project is expected to make an impact on several levels: scientifically, by advancing modeling and material characterization; industrially, by enabling new processes and improved materials; economically, by contributing to European competitiveness; environmentally, by supporting more efficient use of materials and lower emissions; and socially, by helping train skilled researchers and fostering long-term international collaboration. Overall, DIAGONAL aims to contribute to more efficient, adaptable, and sustainable material design that meets current and future engineering and societal needs.
The main research objective of DIAGONAL is the identification and modelling of the mechanical behavior and fracture mechanics of engineering Functionally Graded Materials (FGM). This objective is broken down into the following specific goals:
-Tailoring macroscopic mechanical properties of multi-material FGMs to delay instability-driven ductile failure.
-Virtual design of gradient microstructures of FGMs to mitigate void-growth-driven ductile failure.
-Engineering the crack path in FGMs to enhance the apparent fracture toughness.
-Exploiting FGM coatings to prevent contact-induced fracture in tribological applications.
-Developing numerical methods for the optimization of damage-tolerant FGM designs.
The project has made significant progress toward these objectives. For example:
-We have performed mechanical testing and finite element modeling of notched samples in Hadfield steel single crystals to investigate ductile failure behavior in the absence of graded variation. The introduction of graded microstructures will be addressed in the next project phase.
-We have conducted linear stability analyses to model the onset of necking in FGM multi-materials. In the upcoming phase, this will be extended to capture the development of shear bands.
-We have carried out plate impact experiments on functionally graded specimens with compositional variation through the thickness to study the influence of material gradation on spall strength and the location of fracture initiation.
-We have initiated advanced modeling of protective coatings to understand their effectiveness in preventing fracture. The next step will include functionally graded features to optimize material performance and enhance fracture resistance.
-We have employed phase-field methods to model fracture phenomena at FGM interfaces, focusing on how compositional gradients and material transitions influence crack initiation, propagation, and overall fracture toughness.
-Tailoring macroscopic mechanical properties of multi-material FGMs to delay instability-driven ductile failure.
-Virtual design of gradient microstructures of FGMs to mitigate void-growth-driven ductile failure.
-Engineering the crack path in FGMs to enhance the apparent fracture toughness.
-Exploiting FGM coatings to prevent contact-induced fracture in tribological applications.
-Developing numerical methods for the optimization of damage-tolerant FGM designs.
The project has made significant progress toward these objectives. For example:
-We have performed mechanical testing and finite element modeling of notched samples in Hadfield steel single crystals to investigate ductile failure behavior in the absence of graded variation. The introduction of graded microstructures will be addressed in the next project phase.
-We have conducted linear stability analyses to model the onset of necking in FGM multi-materials. In the upcoming phase, this will be extended to capture the development of shear bands.
-We have carried out plate impact experiments on functionally graded specimens with compositional variation through the thickness to study the influence of material gradation on spall strength and the location of fracture initiation.
-We have initiated advanced modeling of protective coatings to understand their effectiveness in preventing fracture. The next step will include functionally graded features to optimize material performance and enhance fracture resistance.
-We have employed phase-field methods to model fracture phenomena at FGM interfaces, focusing on how compositional gradients and material transitions influence crack initiation, propagation, and overall fracture toughness.
The project will generate new design principles to enhance mechanical performance in both ductile and brittle Functionally Graded Materials. Its outcomes are relevant to sectors like aerospace, civil engineering, transportation, and defense, where strong, lightweight, and sustainable materials are increasingly in demand. Through international collaboration, DIAGONAL combines theoretical, computational, and experimental work to deepen scientific understanding and support real-world applications.