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ABSTRACT The objective of this work was the evaluation of crack growth resistance curves ( J-R curves) of commercial GLARE® 3 5/4 laminates at −50 °C. The experimental evaluation of these curves was performed on 50-mm-wide compact tension specimens through the unloading compliance technique. The tests were based on the ASTM E1820 standard with minor modifications. Additionally, tensile tests were also performed at −50 °C on dogbone specimens according to the ASTM E8M standard. Comparisons between low and room temperature properties indicate that the material preserves both its tensile strength and fracture toughness at −50 °C, although low temperature J-R curves presented smaller slopes than the room temperature ones after the onset of stable crack growth. [ABSTRACT FROM AUTHOR]

Fatigue crack propagation (FCP) under constant and variable amplitude loading in base metal (BM), weld metal (WM) and heat affected zone (HAZ) of longitudinal welded joints of an API X-70 pipeline steel was investigated. Constant amplitude loading tests were performed at R = 0.1 and 0.5, whereas for variable amplitude testing single peak tensile overloads (OLs) alternating between 75 and 100% of maximum load were applied at 2.5 mm intervals in crack growth. Results of SE(B) specimens tested under constant and variable amplitude loading revealed that BM, WM and HAZ regions subjected to R = 0.5 and low Δ K-values presented the highest crack growth rates. At higher Δ K values FCP rates in all the studied regions were similar and the R effect on FCP rate was no more observed. Crack growth retardation due to OLs was observed at the three studied regions, showing a decrease on the FCP delay with a decreasing on Δ K. [ABSTRACT FROM AUTHOR]

Fibre-metal laminates (FMLs) are structural composites designed with the aim of producing very low fatigue crack-propagation rate, damage-tolerant and high-strength materials, if compared to aeronautical Al alloys. Their application in aeronautical structures demands a deep knowledge of a wide set of mechanical properties and technological values, including both fracture toughness and residual strength. The residual strength of FMLs have been traditionally determined by using wide centre-cracked tension panels M(T). The use of this geometry requires large quantities of material and heavy laboratory facilities. In this work, fracture toughness ( JC) of some unidirectional FMLs laminates was measured using a recently proposed methodology for critical fracture toughness evaluation on compact tension C(T) and single-edge bend SE(B) specimens. Additionally, residual strength values of wider M(T) specimens with different widths ( W from 150 to 200 mm) and several crack to width ratios (2 a/W) were experimentally obtained. Some experimental residual strength values of M(T) specimens ( W from 150 to 400 mm and different 2 a/W ratios) of Arall were also obtained from the bibliography. Based on JC results from C(T) and SE(B) specimens, and either using or not using crack-tip plasticity corrections, the residual strengths of the M(T) specimens were predicted and compared to the experimental ones. The results showed good agreement, especially when crack-tip plasticity corrections were applied. [ABSTRACT FROM AUTHOR]