26 research outputs found
Effect of solute content and temperature on the deformation mechanisms and critical resolved shear stress in Mg-Al and Mg-Zn alloys
The influence of solute atoms (Al and Zn) on the deformation mechanisms and
the critical resolved shear stress for basal slip in Mg alloys at 298 K and 373
K was ascertained by micropillar compression tests in combination with
high-throughput processing techniques based on the diffusion couples. It was
found that the presence of solute atoms enhances the size effect at 298 K as
well as the localization of deformation in slip bands, which is associated with
large strain bursts in the resolved shear stress ()-strain
() curves. Deformation in pure Mg and Mg alloys was more homogeneous
at 373 K and the influence of the micropillar size on the critical resolved
shear stress was much smaller. In this latter case, it was possible to
determine the effect of solute content on the critical resolved shear stress
for basal slip in Mg-Al and Mg-Zn alloys
Interface characterization in fiber-reinforced polymer-matrix composites
A novel methodology is presented and applied to measure the shear interface strength of fiber-reinforced polymers. The strategy is based in fiber push-in tests carried out on the central fiber of highly-packed fiber clusters with hexagonal symmetry, and it is supported by a detailed finite element analysis of the push-in test to account for the influence of hygrothermal residual stresses, fiber constraint and fiber anisotropy on the interface strength. Examples of application are presented to determine the shear interface strength in carbon and glass fiber composites reinforced with either thermoset or thermoplastic matrices. In addition, the influence of the environment (either dry or wet conditions) on the interface strength in C/epoxy composites is demonstrated.This investigation was supported by the Ministerio de Ciencia e Innovación of Spain through the Grant MAT2012-37552, by the Comunidad de Madrid through the program DIMMAT (P2013/MIT2775), and by the European Community's Seventh Framework Programme FP7/2007-2013 under Grant Agreement 213371 (MAAXIMUS, www.maaximus.eu). In addition, the support of Airbus through the project SIMSCREEN ("Simulation for Screening Properties of Materials") is gratefully acknowledged
High temperature strength retention of Cu/Nb nanolaminates through dynamic strain ageing
The mechanical properties of Cu/Nb metallic nanolaminates with different
layer thickness (7, 16, 34 and 63 nm) were studied by means of micropillar
compression tests from room temperature to 400 C. Both strain-rate jump and
constant strain rate tests were carried out and they showed evidence of dynamic
strain ageing in the nanolaminates with 7, 16 and 34 nm layer thickness
deformed at 200 C. Dynamic strain ageing was accompanied by a reduction of the
strain rate sensitivity to 0, high strength retention at 200 C and the
development of shear localization of the deformation at low strains (5%-6%)
that took place along the Nb layers in the nanolaminates. Atom probe tomography
of the deformed specimens revealed the presence of O in solid solution in the
Nb layers but not in the Cu layers. Thus, diffusion of O atoms to the mobile
dislocations in Nb was found to be the origin of the dynamic strain ageing in
the Cu/Nb nanolaminates around 200 C. This mechanism was not found at higher
temperatures (400 C) because deformation was mainly controlled by
stress-assisted diffusion in the Cu layers. This discovery shows a novel
strategy to enhance the strength retention at high temperature of metallic
nanolaminates through dynamic strain ageing of one the phases