in this paper, a systematic study on the effects of particle size and hybrid of two different size of silica nanoparticles on the toughening mechanisms of bisphenol-a epoxy was conducted. nanosilica particles with mean diameter of 17 nm and 65 nm were blended into epoxy system. probable synergy effects of these two nanoparticles on young’s modulus and yield strength have been investigated. resu...

In order to design composites and laminated materials, it is necessary to understand the issues that govern crack deflection and crack penetration at interfaces. Historically, models of crack deflection have been developed using either a strength-based or an energy-based fracture criterion. However, in general, crack propagation depends on both strength and toughness. Therefore, in this paper, ...

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...

A detailed experimental and numerical investigation has been performed to validate large scale numerical simulations of dynamic crack propagation, branching, deflection, and penetration at interfaces in brittle homogeneous materials. High-speed photography in conjunction with the dynamic photoelasticity has been used to observe real-time failure mode transition mechanism at the interfaces. Wedg...

This paper presents the results of an experimental program conducted for evaluating the performance of corrosion damaged HSC beams strengthened with GFRP laminates. Five Beam specimens of size 150x250x3000 mm were caste and tested for the present investigation. One beam specimen was neither corroded nor strengthened to serve as reference. Two beams were corroded to serve as corroded control. A ...

The problem of crack deflection in bimaterial systems is considered in this paper. The material combinations may be of piezoelectric-piezoelectric, or one is piezoelectric and the other is not. Based on the Stroh formulation for anisotropic material, Green’s functions for various bimaterial combinations are presented within the framework of two-dimensional electroelasticity, allowing the crack ...

Problem statement: This study showed the results of an experimental investigation on the strengthening of corrosion damaged reinforced concrete beams with unidirectional cloth glass fiber reinforced polymer (UDCGFRP) laminates. Approach: All the beam specimens 150×250×3000 mm were cast and tested for the present investigation. One beam specimen was neither corroded nor strengthened to serve as ...

Coherent twin boundaries (CTBs) in nano-twinned materials could improve crack resistance. However, the role of the CTBs during crack penetration has never been explored at atomic scale. Our in situ observation on nano-twinned Ag under a high resolution transmission electron microscope (HRTEM) reveals the dynamic processes of a crack penetration across the CTBs, which involve alternated crack ti...

A 2-dimensional, elastic-plastic finite element model has been developed to simulate plasticity induced crack closure in slanted and deflected cracks growing outside the small scale yielding (SSY) regime. The finite element model allows for contact between deformable surfaces to capture the complex contact interaction between the crack faces. Coulomb’s friction law has been used to model fricti...

High strength, wrought 7xxx (Al-Zn-Mg) and Al-Li based alloys show a propensity for fatigue macroscopic crack deflections aligned along grain boundaries. The present work reports a study on a 3 rd generation Al-Li based alloy in the form of a thick AA2297 (Al-Cu-Li alloy) plate, where it was found that although the lithium containing material may indeed be more susceptible to mixed mode grain b...