A study has been made of the fatigue-crack propagation properties of a series of laminated Nbreinforced Nb3Al intermetallic-matrix composites with varying microstructural scale but nominally identical reinforcement volume fraction (20 pct Nb). It was found that resistance to fatigue-crack growth improved with increasing metallic layer thickness (in the range 50 to 250 mm) both in the crack-divi...

26 LLE Review, Volume 77 Deciding when to replace spot-damage-afflicted fused-silica optics or, in the case of inaccessible, space-based lasers, predicting the useful service life of fused-silica optics before catastrophic, pulsed-laser-driven crack growth shatters a part has recently become simpler. By empirically deriving a rule for laser-driven crack growth in fused silica as a function of t...

The aging-related deterioration of the fracture properties of bone, coupled with higher life expectancy, is responsible for increasing incidence of bone fracture in the elderly; consequently, an understanding of how these fracture properties degrade with age is essential. In this study, ex vivo fracture experiments have been performed to quantitatively assess the effect of age on human cortical...

Environmentally dependent subcritical crack growth, or stress-corrosion cracking, along ceramic-metal interfaces is studied for the silica glass-copper system. Tests were conducted in various gaseous and liquid environments in order to determine their relative effects on stress-corrosion cracking and to gain some insight into the mechanisms that control interfacial crack growth. In agreement wi...

The objective of this investigation was to develop an innovative methodology for life and reliability prediction of hot-section components in advanced turbopropulsion systems. A set of generic microstructure-based time-dependent crack growth (TDCG) models was developed and used to assess the sources of material variability due to microstructure and material parameters such as grain size, activa...

It is generally accepted that the fatigue crack growth (FCG) depends mainly on the stress intensity factor range (DK) and the maximum stress intensity factor (Kmax). The two parameters are usually combined into one expression called often as the driving force and many various driving forces have been proposed up to date. The driving force can be successful as long as the stress intensity factor...

There exist two fracture mechanisms in facesheets of sandwich composites consisting of the 08 and 908 plies, namely crack growth and crack blocking. The former is undesired since it may lead to failure of facesheets and even the core in sandwich composites. A shear-lag model is developed in this article and it gives a simple criterion governing these two mechanisms. It is established that, for ...

The growth of a single cylindrical hole ahead of a blunt crack tip was studied using large deformation finite element analysis in three-point bend specimens with different precrack depth. The effect of small second phase particles was taken into account by incorporating Gurson’s constitutive equation. The effects of strain hardening and the initial distance from the hole to the crack tip were a...

The propagation of cracks in graded materials under monotonic and cyclic loading was investigated via experiment and simulation. Graded alumina/epoxy composite specimens exhibiting a variation in composition from 5% to 65% epoxy, representing a twenty-fold variation in Young’s modulus, across a region of width between 6 and 20 mm, were produced by a multistep infiltration technique. Crack initi...