Toughening Mechanisms in Quasi-Brittle Materials (Nato Science Series E: (195))

A variety of ceramic materials has been recently shown to exhibit nonlinear stress­ strain behavior. These materials include transformation-toughened zirconia which undergoes a stress-induced crystallographic transformation in the vicinity of a propagating crack, microcracking ceramics, and ceramic-fiber reinforced ceramic matrices. Since many of these materials are under consideration for structural applications, understanding fracture in these quasi-brittle materials is essential. Portland cement concrete is a relatively brittle material. As a result mechanical behavior of concrete, conventionally reinforced concrete, prestressed concrete and fiber reinforced concrete is critically influenced by crack propagation. Crack propagation in concrete is characterized by a fracture process zone, microcracking, and aggregate­ bridging. Such phenomena give concrete toughening mechanisms, and as a result, the macroscopic response of concrete can be characterized as that of a quasi-brittle material. To design super high performance cement composites, it is essential to understand the complex fracture processes in concrete. A wide range of concern in design involves fracture in rock masses and rock structures. For example, prediction of the extension or initiation of fracture is important in: 1) the design of caverns (such as underground nuclear waste isolation) subjected to earthquake shaking or explosions, 2) the production of geothermal and petroleum energy, and 3) predicting and monitoring earthquakes. Depending upon the grain size and mineralogical composition, rock may also exhibit characteristics of quasi-brittle materials. Front Matter....Pages i-xi Front Matter....Pages 1-1 Fracture Properties of SiC-Based Particulate Composites....Pages 3-17 Crack Bridging Processes in Toughened Ceramics....Pages 19-33 Fracture Process Zone in Concrete and Ceramics - A Matter of Scaling....Pages 35-46 Report on Session 1: Fracture of Ceramics with Process Zone....Pages 47-49 Front Matter....Pages 51-51 Microcracking and Damage in Concrete....Pages 53-65 Cracking, Damage and Fracture in Stressed Rock: A Holistic Approach....Pages 67-89 Test Methods for Determining Mode I Fracture Toughness of Concrete....Pages 91-124 Report on Session 2 Fracture in Concrete and Rock....Pages 125-127 Front Matter....Pages 129-129 Rate Effect, Size Effect and Nonlocal Concepts for Fracture of Concrete and Other Quasi-Brittle Materials....Pages 131-153 Micromechanics of Deformation in Rocks....Pages 155-188 Asymptotic Analysis of Cohesive Cracks and Its Relation with Effective Elastic Cracks....Pages 189-202 Toughening Mechanisms in Quasi-Brittle Materials....Pages 203-205 Front Matter....Pages 207-207 Microstructure, Toughness Curves and Mechanical Properties of Alumina Ceramics....Pages 209-233 Creep Damage Mechanisms in Hot-Pressed Alumina....Pages 235-247 Study of the Fracture Process in Mortar with Laser Holographic Measurements....Pages 249-265 Reporter Comments on Session 4 - Experimental Observations....Pages 267-268 Front Matter....Pages 269-269 The Fracture Process Zone in Concrete....Pages 271-286 Characterization of the Fracture Behavior of Ceramics through Analysis of Crack Propagation Studies....Pages 287-311 A Review of Experimental Methods to Assess Damage during Fracture of Rock, Concrete and Reinforced Composites....Pages 313-328 Similarities between Fracture Processes in Concrete, Rock and Ceramics: Recorders Report to Session 5 ’Experimental Methods to Assess Damage’....Pages 329-335 Front Matter....Pages 337-337 A review of some theories of Toughening mechanisms in Quasi-Brittle materials....Pages 339-353 On the Form of Micromechanical Models of the Brittle Deformation of Solids....Pages 355-372 On the Relationship between Fracturing of a Microcracking Solid and Its Effective Elastic Constants....Pages 373-378 Report of Session 6: Theoretical Micromechanics Based Models....Pages 379-382 Front Matter....Pages 383-383 Determination of Fiber-Matrix Interfacial Properties of Importance to Ceramic Composite Toughening....Pages 385-403 Quasi-Ductile Behaviour of Carbon-Reinforced Carbon....Pages 405-423 The Fracture Resistance of Brittle Matrix Composites....Pages 425-439 Session 7 Discussion....Pages 441-443 Front Matter....Pages 445-445 Research Challenges in Toughness Development of Fiber Reinforced Cementitious Composites....Pages 447-466 Failure Characterisation of Fibre—Reinforced Cement Composites with R—Curve Characteristics....Pages 467-505 Characterization of Interfacial Bond in FRC Materials....Pages 507-527 Summary of Session 8: Fracture Toughness of Fiber-Reinforced Cement Composites....Pages 529-537 Front Matter....Pages 539-539 Growth of Discrete Cracks in Concrete under Fatigue Loading....Pages 541-554 Creep and Creep Rupture of Structural Ceramics....Pages 555-575 Fracture of Concrete at High Strain-Rate....Pages 577-596 Summary of Session 9: Strain Rate, Thermal, Time and Fatigue Effects....Pages 597-602 Back Matter....Pages 603-612 Proceedings of the NATO Advanced Research Workshop, Evanston, Illinois, July 16-20, 1990