Investigation of Influence of Nano-Reinforcement on the Mechanical Properties of Composite Materials

Abstract

The present work studies the possibility to decrease the formation of micro and nano cracks around short fibres in fibre-reinforced concrete (FRC) composite with the help of nano-reinforcement, which is carbon nanotubes, or micro reinforcement, which is carbon short fibres and nano-fillers. Tensile and bending strength of FRC depends on the spatial distribution of fibres inside a material, type of fibre and cement matrix, as well as an effective micromechanical work of each fibre while pulling out of the concrete matrix. Shrinkage stresses, acting in the matrix in the vicinity of a fibre, lead to the formation of micro-cracks. Such micro-cracks were observed experimentally and were investigated numerically performing broad modelling based on the finite element method (FEM). The investigation was focused on the micromechanical behaviour of a single steel fibre in a cement matrix. Numerical modelling results demonstrated a high level of shrinkage overstresses around steel fibres in concrete. The role of nano and micro admixtures, nanotubes, short carbon fibres as well as the role of water/cement ratio in a high performance concrete matrix, changing (increasing or decreasing) the friction force between the matrix and the steel fibre, were investigated experimentally by way of per­forming a single fibre pull-out tests. The high scatters of experimental results were obtained in performed pull-out tests. At the same time, for the same series of samples, a positive role of micro and nano admixtures and carbon nanotubes in the increase of pull-out force was recognised.

Testing the Physical and Mechanical Properties of Polyacrylonitrile Nanofibers Reinforced with Succinite and Silicon Dioxide Nanoparticles

“…In the past, one of the main engineering challenges was the development, introduction, and mass production of efficient materials in all industrial areas. Different fiberreinforcement options are used in various fields [1][2][3][4][5], including the use of various materials and technologies [6][7][8][9]. Due to its superior physical characteristics, such as low density, thermal constancy, high strength, and modulus of elasticity, polyacrylonitrile (PAN) is a commercially important semicrystalline polymer [10,11].…”

Failure Analysis of Ultra High-Performance Fiber-Reinforced Concrete Structures Enhanced with Nanomaterials by Using a Diffuse Cohesive Interface Approach

“…Moreover, some authors identified the optimal amount of combined steel microfibers and carbon nanofibers embedded in a UHPFRC providing a balanced increase in the flexural and compressive strengths [ 35 ]. Furthermore, a significant increase in the bond between cement matrix and steel microfibers is obtained in [ 36 ], via the incorporation of a small percentage of nanotubes, thus leading to a higher concrete pull-out strength. Specifically, the above-mentioned enhanced bond strength, associated with a stronger crack bridging effect in the proximity of the steel fibers, is capable to inhibit the micro-crack onset and to delay the subsequent fracture propagation processes.…”

Concrete Reinforced by Hybrid Mix of Short Fibers under Bending

“…Short fibers may be used as the main or the secondary reinforcement (in combination with rebars), bearing the bending moments and the shear stresses. Several papers reported on the research into the properties of the concrete matrix successfully reinforced with various fibers made of various materials [19][20][21][22][23] and using different methods [24][25][26]. Fibers can be easily introduced into the concrete during ingredient mixing.…”