The book explores the two opposite natural trends of composite systems: (i) order and structure emerging from heterogeneity and randomness, and (ii) instability and chaos arising from simple nonlinear rules. Providing insights into the rapidly growing field of complexity sciences, the book focuses on the role of complexity in fracture mechanics. It firstly discusses the occurrence of self-similarity and fractal patterns in deformation, damage, fracture, and fragmentation of heterogeneous materials and the apparent scaling of the nominal mechanical properties of disordered materials, as well as of the time-to-failure after fatigue and creep loading. Then the book addresses criticality in the acoustic emissions from damaged structures and tectonic faults. Further, it examines the snap-back instability in the structural behavior of relatively large composite structures in the framework of catastrophe theory, and lastly describes the transition toward chaos in the dynamics of cracked elements.

Stress Concentration at the Notch Root.- Stress Intensification at the Crack Tip.- Stress Intensification at the Vertex of a Re-entrant Corner.- Energy Approach to Fracture Mechanics.- Mixed-mode Crack Propagation.- Nonlinear Crack Models.- Size-scale Transition from Ductile to Brittle Failure.- Mechanical Behaviour of Reinforced Elements.- Fractal Scaling of Fracture Energy, Tensile Strength, and Ultimate Strain.- Fractional Calculus Applied to Fractal Media and Nonlocal Continua.- Fragmentation, Comminution, Drilling, and Wear.- Nonlinear and Chaotic Behaviour in the Vibration of Cracked Bodies.- Debonding and Decohesion at the Interface Between Dissimilar Media.- Scaling in Fatigue and Creep Mechanisms.- Acoustic Emission and Critical Phenomena in Structural Elements and Earth Crust.