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The impacts associated with alternative methods of agricultural production, and the factors that drive their adoption, are critically dependent on the scale at which they are applied. Using organic farming as a case study, this project operating from 2006–2009 in the UK, will undertake an integrated assessment of scale effects by studying matched sets of farms situated in landscapes with high and low concentrations of organic farming. Clusters of organic and conventional farms to work with have been identified in the South West and Midlands region of England.

The report summaries a closely coupled experimental and theoretical investigations of various stages of Fracture Process: (1) accumulation of 'damage' on submicroscopical and microscopical scales leading to crack initiation; (2) slow (subcritical) crack growth and an evolution of the damage zone; (3) transition to dynamic crack growth and the catastrophic failure. The experimental part of the program is focused on the observation and quantitative characterization of damage preceding and accompanying crack initiation and growth. A special experimental setup for studying the fracture process under variable stress field is reported in Chapter 2. A leading role of crack-damage interaction in fracture process is well documented. A new formalism for solution of crack-microcrack array interaction problem and its successful implementation in the evaluation of crack layer driving forces is presented in Chapter 3. A new model of the process zone, which generalizes the well-known Dagdale-Barenblatt model is presented in Chapter 4. A new measure for material toughness and the prediction of R-curve behavior illustrate the practical application of our model. Experimental examinations of our model under various test conditions are reported in Chapters 4, 5 and 6. The development of the constitutive equations for Crack Layer evolution and their experimental examinations under stress relaxation, fatigue and creep conditions are reported in Chapters 5 and 6. An accelerated test procedure and the formulation of crack layer instability criteria as a substitution for the conventional fracture toughness parameters are also discussed in Chapter 6.

Multiple experience on macroscopically identical 3D carbon-carbon (C/ C) composite specimens show that the fracture behavior displays the main features of a stochastic process which reflects the random nature of the strength field. The critical load is random and a sample set of crack trajectories displays a Poisson's type diffuse character. Crack trajectories are unique for each individual experiment (no two coincide). The crack appears to propagate stepwise (a sequence of local failures) through a random field of defects which is constrained by the orthotropic architecture of the yarn bundles. Keywords: Carbon carbon composite.

Results of a scouting program of research in foundations of mesomechanics are presented. A special case of Weyl's geometry was employed to derive equations of thermoelasticity on pure geometrical ground; this demonstrates the potential of using Weyl's geometry as a model of the geometry of the material space. Experimental methods of finding fractal dimensions of fracture surfaces were examined (for various materials) together with a method of fracture profile simulation; the results contribute to developing experimental techniques of studying metric properties of the material space. A new dynamic crack propagation equation was derived on the basis of the least action principle; this is a first step of applying the Lagrangian formalism to deriving equations of continuous damage evolution.