Reviews the latest information and experimentation on the fracture-toughness testing of materials using specimens that are chevron notched, a procedure that has been an ASTM standard only since December 1989. The 13 papers were presented at a symposium in Indianapolis, May 1991; they include studies

Aluminium-Lithium (Al–Li) alloys have been of interest since the 1950s when they were first used on a military aircraft. Having lithium as the main alloying element in Al alloys is attractive since (i) each 1 wt% Li reduces the density by ~3% and increases modulus by ~5%, and (ii) high strengths can be achieved by precipitation-hardening. During the 1980s, extensive research and development was carried out on alloys with high lithium contents (>2 wt%≡~8 at%) such as AA 8090 (Al 2.4 Li 1.2 Cu 0.7 Mg 0.12 Zr) (wt%). The mechanical properties of these ‘second-generation’ Al–Li alloys, however, did not match those of conventional Al (-Zn)-Mg-Cu alloys, and the lower fracture toughness of these alloys (for equivalent strengths was a particular problem. Thus, 2nd generation Al–Li alloys did not see widespread use. The experience with 2nd generation Al–Li alloys led to the development of ‘3rd generation’ alloys with lower Li contents (0.75–1.7 wt%), and some of these alloys have a better overall balance of properties, including fracture toughness, than the best available conventional Al alloys. These 3rd generation Al–Li alloys should therefore see extensive use in future civil and military aircraft. This chapter on fracture toughness and fracture modes of aerospace Al–Li alloys outlines why fracture toughness is important for aerospace structures and components, and summarises testing procedures and terminologies in regard to plane-strain and plane-stress fracture toughness. The relationships between fracture toughness/fracture modes and microstructural features such as grain morphology, constituent particles, impurity phases, matrix precipitates, grain-boundary precipitates, and grain boundary segregation, are then discussed. Proposed explanations for the low fracture toughness of 2nd generation Al–Li alloys, associated with low-energy intergranular and transgranular shear fractures, are discussed in some depth, followed by a summary of the alloy-design principles behind the development of 3rd generation Al–Li alloys with a much improved resistance to low-energy fracture modes. Quantitative data for fracture toughness of 2nd and 3rd generation Al–Li alloys in comparison with conventional Al alloys are provided, showing that 3rd generation Al–Li alloys have outstanding combinations of toughness and strength combined with reduced densities. The superior toughness of 3rd generation Al–Li alloys compared with 2nd generation alloys is reflected in the differences in fracture-surface topography and fracture path. The chapter concludes with a summary of the current and proposed uses of 3rd generation Al–Li alloys in aircraft structures and components

This book derives from the invited IUTAM Symposium in September 1993. The contributions discuss recent advances in fracture mechanics studies of concrete, rock, ceramics and other brittle disordered materials at micro and structural levels. It draws together research and new applications in continuum, damage and fracture mechanics approaches.

This volume is part of the Ceramic Engineering and Science Proceeding (CESP) series. This series contains a collection of papers dealing with issues in both traditional ceramics (i.e., glass, whitewares, refractories, and porcelain enamel) and advanced ceramics. Topics covered in the area of advanced ceramic include bioceramics, nanomaterials, composites, solid oxide fuel cells, mechanical properties and structural design, advanced ceramic coatings, ceramic armor, porous ceramics, and more.