DESCRIPTION OF WORK (WORK PACKAGES)

WP1 – Upscaling (Research)

The main objective of WP1 is to establish fundamentals by which models at a lower scale of observation can feed into models at a higher scale of observation. This can be done at various scales. In particular, we will aim for the following:

• Atomistics: Use of first principles based on atomic/molecular and sub atomic/sub molecular interactions by employing density functional theory (DFT) and lattice dynamics (LD) techniques to derive physics and chemistry informed models for material deformation, in particular in the presence of flaws.
• Dislocation Dynamics: Elaborate on discrete dislocation dynamics (DDD) simulations; derive a continuum theory where dislocation dynamics dictates plastic flow and couple this to the atomic processes at crack tips.
• Crystal Plasticity: Analyse crack nucleation and propagation through crystals with increasing complexity: from static fracture of single crystals, to fatigue fracture of poly-crystals, covering various degrees of ductility, focusing on the interaction between crystallographic planes, dislocations and the fracture.
• Relevant training activities including: a short course on ‘Discrete and Continuum Modelling of Crystal Plasticity’, a short course on ‘Regularised Models of Fracture’ and a two day course on ‘Upscale Modelling and Techniques on Lower Levels of Observation’ will be developed for the benefit of the FRAMED consortium and a wider audience, will focus on how length scale parameters appear in the various formalisms, and how these length scale parameters affect higher levels of observation.

WP2 – Stochasticity and Disorder (Research)

The main objective of WP2 is to quantify how randomness affects material behaviour across the scales. This has a number of research questions that will be addressed:

• Stochasticity: Which fields of state variables are affected by randomness and to what extent? The focus will be on the degree of fluctuation versus the degree of correlation, and how this feeds into upscaling principles.
• Disorder: Investigate how disorder at a particular scale of observation influences the growth or arrest of defects. Investigate how this will propagate across the scales.

There is a clear overlap with WP1 (“Upscaling”), but also with WP5 (“Experimental validation”) in order to decide on the statistical representativeness of experiments. Relevant training activities will focus on the fundamentals of statistical mechanics and the micro-mechanics of defects in its relation to disorder.

WP3 – Multiscale Modelling Framework (Research)

The main objective is to establish a unifying strategy that is suited to transfer input from WP1 “Upscaling” and WP2 “Stochasticity and Disorder” to higher scales of observation, and relate this to the validation from WP5. The soreceived input will be utilised for constructing a new physically-informed fracture framework, accounting for new phenomenology beyond conventional elasticity models. This will involve combined gradient-stochastic models also accounting for internal times; i.e. material times or time delay parameters associated with the incubation processes of the dominant micro/nano structures before they actively participate in the fracture process. There are three main aspects that WP3 will focus upon:

• A powerful modelling paradigm is so-called nonlocal or gradient physics, whereby higher-order derivatives represent the influence of lower-scale contributions (WP1) and/or the effects of randomness (WP2). We will explore and (where needed) expand the gradient mechanics framework for elasticity, plasticity damage and multi-physics models, i.e. coupled thermos-chemo-mechanical and opto-electro-mechanical models. The material length parameters present in gradient physics will ensure scalability of results.
• The driver mechanisms for crack propagation must be identified in each modelling framework. We will use the concept of “material/configurational forces” as a fundamental geometry-optimising concept for configurational change and, thus, fracture.
• As regards the numerical implementation, we will use modern finite element techniques such as isogeometric analysis and goal-oriented adaptive analysis. These need to be adjusted such that they can accommodate both higher-order gradients in various fields and the inclusion of discontinuous fields that describe the cracks.

Relevant training activities will focus on the fundamentals of gradient elasticity/gradient plasticity, material forces, isogeometric analysis and adaptive finite element analysis.

WP4 – Applications (Research)

WP4 will focus on applications; these applications will build on the knowledge gained in the other WPs but they will also steer and inform the work done in the other WPs. In order to let this cross-fertilisation be as effective as possible, we will target a wide range of processes and disciplines: 

• Mechanical/Civil Engineering: Fracture and fatigue failure in conventional engineering materials in, for instance, the automotive industry (metal, polymers) the aerospace industry (composites) and the construction industry (concrete, asphalts), but also natural materials (paper, timber, bone).
• Engineered Materials/Advanced Manufacturing: Fracture and fatigue failure in new, man-made materials obtained through additive manufacturing and 3D printing (cellular foams, micro-truss materials), in particular with relation to stochasticity and disorder.
• Geo-Energy/Mining Applications: induced fracture processes for the purpose of tunnelling, oil/gas recovery (fracking), geothermal energy storage and/or recovery.
• Environmental processes: large scale natural disasters such as landslides, avalanches, earthquakes and volcano eruptions – in particular exploring ways to predict these based on multi-scale fracture and its associated acoustic emissions.
• High Energy Density Storage: Fracture driven by multi-physics environments such as chemo-mechanics and thermomechanics; applications include Li-ion and Na-ion batteries, solar cells, optoelectronics, MEMS/NEMS.
• Bio-Materials: Fracture in hard (bone) and soft (skin, brain) tissues, as well as cells and organelles. Bio-micro/nano structures evolve inhomogeneously, they are governed by internal length/times, and their role in fracture has not been sufficiently accounted for in existing biomechanics models. This will be an entirely novel feature of the project.

WP5 – Validation and Testing (Research)

Although the main focus of the FRAMED project is on modelling, it is clear that no modelling approach can be pursued with confidence unless it is backed up by thorough experimental validation. Of particular interest will be to identify and quantify the relevant material length scales and how these propagate across the scales. Thus, and in the spirit of WP3 (“Multi-scale Modelling Framework”), we will target experimental validation across scales.

• Large scale: fracture and fatigue tests will be carried out on benchmark geometries as well as more industrially relevant problems.
• Small scale: lower scale validation on standardised specimens will take place via indentation tests, Digital Image Correlation techniques and micro-tomography.