The effect of surface free energy on the fracture behaviors of nanoparticle-reinforced composites

By considering the surface free energy effect, an analytical investigation on the fracture behaviors of nanoparticle-reinforced composites was performed in this study. The plastic zones ahead of the crack tips based on the Irwin model were introduced in our analysis, which has a significant influence on the fracture toughness of inelastic structures, especially for polymer and metal matrix composites. Take copper and aluminum nanoparticles as examples, comprehensive parametric studies were conducted to investigate the interaction between a Griffith crack and the nearby nanoparticle. It was found that for nanoparticles with the radius of less than 10 nm, apart from the mechanical property of the nanoparticle, the surface free energy effect plays a dominant role in determining the fracture behaviors of the nanoparticle-reinforced composites. Moreover, taking the surface free energy into account, a decrease in the plastic zone size is obtained, particularly for the crack tip nearer the nanoparticle.

Automatic Adaptive Recovery Stress ES-FEM for Lower-Bound Limit Load Analysis of Structures

The paper proposes a novel automatic adaptive recovery stress edge-smoothed finite element method (ES-FEM) that determines the maximum load capacity of inelastic structures at plastic collapse. This approach performs solely a series of elastic ES-FEM analyses with systematic modulus variations (considering the influences of stress singularity) to converge the collapse load solutions. The smoothed [Formula: see text]-continuous recovery stress field ensures the satisfaction of static admissible stress and yield conformity conditions underpinning lower-bound limit analysis theorems. A modified modulus error function within the newest node bisection algorithm enables automatic mesh refining and coarsening constructions, and fast convergence to the lower-bound collapse limit.

Seismic Reliability-Based Design Approach for Base-Isolated Systems in Different Sites

This study employs the seismic reliability-based design approach for inelastic structures isolated by friction pendulum isolators, considering two different highly seismic Italian sites to provide useful design recommendations. Incremental dynamic analyses are carried out to estimate the seismic fragility of the superstructure and of devices, assuming different structural properties and limit state thresholds. Finally, considering seismic hazard curves of the investigated sites, seismic reliability-based design curves are proposed to derive the dimensions in plan of devices and the ductility demand of the superstructure as a function of both the structural properties and the reliability level expected. The proposed results confirm the possibility of using seismic reliability-based design as a sustainable and applicable approach and represent a large data set to adopt this design methodology in any site with a similar seismic hazard.