Italian Group Fracture (IGF): E-Journals / Gruppo Italiano Frattura
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Mechanisms for Introduction of Pseudo Ductility in Fiber Reinforced Polymer Composites- A Review
Get PDFAdvanced polymer matrix composites are gaining the market in their way due to their exceptional specific stiffness, specific strength, fatigue, and corrosion resistance in the field of Auto-Tech, Aero-Tech, Biotech, etc. However, the lack of ductility and catastrophic failure has limited their application in these areas. Hence there is a need to explore means and protocols for designing the reduced factor of safety with high-performance toughened composites. To address this problem, a new generation of high-performance composites with pseudo-ductile or ductile behavior is needed. The ongoing High-Performance Ductile Composite Technology (HiPerDuCT) program jointly between the University of Bristol U.K and Imperial College London to address this challenge by developing newer materials. The fiber architectures made under this project gave a more gradual failure rather than catastrophic failure which improves the mechanical properties. This paper mainly focuses on addressing this evolution of pseudo ductility in fiber-reinforced composites. In addition to this, an attempt has been made to newer possible fiber positions in matrix materials for inducing reasonable ductility in composites
Influence of Internal Technological Defects on the Mechanical Properties of Structural CFRP
Get PDFThe use of carbon-fiber composite materials (CFRP) in critical cases implies an increase in the resistance to the stability of their mechanical properties. For the purpose of in-depth analysis of defects in the experiments, an integrated approach to mechanical flaw detection and testing of CFRP is used. To determine the parameters of defects in ultrasonic diagnostic sensors and the method of infrared thermography. The main technological defects of structural carbon fiber in samples of the internal "glueline defect", are three geometric shapes (circle, square, rectangle) and a "buckling" inner layer. As a result of flaw detection of individual samples by ultrasonic diagnostics, data were obtained on the shape and size of defects such as "glueline defect" and "buckling". As a result of the study, tensile testing of the samples with and without defects was carried out using the Vic 3D system, the AMSY-6 acoustic emission system, and the FLIR SC7700M thermal imaging system. The tensile strength, elastic modulus, Poisson's ratio, and maximum fracture strains of the studied CFRP without defects and with defects are obtained. The effect of defective zones on the main mechanical parameters is determined. The investigated defects lead to a decrease in strength and elastic characteristics by at least 15% and 5%, respectively
A review of the application of the simulated annealing algorithm in structural health monitoring (1995-2021)
Get PDFIn recent years, many innovative optimization algorithms have been developed. These algorithms have been employed to solve structural damage detection problems as an inverse solution. However, traditional optimization methods such as particle swarm optimization, simulated annealing (SA), and genetic algorithm are constantly employed to detect damages in the structures. This paper reviews the application of SA in different disciplines of structural health monitoring, such as damage detection, finite element model updating, optimal sensor placement, and system identification. The methodologies, objectives, and results of publications conducted between 1995 and 2021 are analyzed. This paper also provides an in-depth discussion of different open questions and research directions in this area
Effect of date palm and polypropylene fibers on the characteristics of self-compacting concretes: comparative study
Get PDFThis article presents the results of a comparative experimental study on the influence of date palm fibers to replace polypropylene fibers used as reinforcement in self-compacting concrete (SCC). Indeed, the use of polypropylene fibers makes it possible to reduce the plastic shrinkage of concrete. Date palm fibers have mechanical characteristics (tensile strength and elasticity modulus) largely sufficient to replace polypropylene fibers. The use of natural fibers has several advantages, they are natural, renewable, have no affect the environment and require little energy for their transformation, unlike synthetic fibers. In this comparative study, polypropylene fiber is used as control material and date palm fiber as study material. The results obtained show that the two types of fibers decrease the fluidity and the compressive strength but increase the flexural strength and decrease the shrinkage. Date palm fibers delay the appearance of cracks more than polypropylene fibers. Date palm fibers guarantee the best results of SCCs in fresh and hardened stat
Impact behavior of gravity cast AlSi10Mg alloy: Effect of hot isostatic pressing and innovative high pressure T6 heat treatment
Get PDFIn the present study the impact behavior of gravity casting AlSi10Mg alloy was evaluated with an instrumented Charpy pendulum. The effect of hot isostatic pressing, also followed by a T6 treatment, was analyzed in comparison with samples in the as-cast, annealed and T6 conditions. Furthermore, the effect of the innovative high-pressure T6 was investigated.It was found that the hot isostatic pressing is able to ensure densification of the alloy with an increase in both hardness and energy absorbed during impact. The T6 treatment performed at atmospheric pressure after the hot isostatic pressing is able to increase hardness and peak force. At the same time, the innovative high-pressure T6 is able to ensure similar results than those of hot isostatic pressing followed by T6, leading to a significant decrease in the treatment duration and costs and reducing the carbon footprint of the manufacturing process
Computer simulation of stress-strain states in zygomatic bones after complex installation of implants
Get PDFThe research addresses evaluation of stress-strain state (SSS) in the “zygomatic bones–implants–denture base” system by varying the type and number of the zygomatic implants, as well as applying loads. The load magnitude was varied over a wide range, characteristic of the mastication process. Changing the adhesion conditions at the “zygomatic implant–bone tissue” interface varied both the level of maximum stress and the location of the critical stress concentrator. The local violation of the integrity of bone tissue in the skull was one of the key reasons for the redistribution of stresses in the “zigomatic implantdenture base” system. Such a phenomenon should be primarily taken into account when choosing the standard sizes of installed zygomatic implants in order to reduce the compliance of weakened areas of the skull (as the basis of the load-bearing structure). Based on the results of the FEM-based computer simulation, the algorithm was proposed for planning prosthetic treatment, which involves the iterative method for selecting both size and location of installing zygomatic implants depending on the results of the SSS calculation and the onset of a critical condition (primarily in bone tissue at the contact area with zygomatic implants)
A nonlocal elasticity theory to model the static behaviour of edge-cracked nanobeams
Get PDFIn the present paper, the mechanical behaviour of edge-cracked nanobeams under Mixed-Mode loading is analytically investigated by means of the Stress-Driven nonlocal model. Firstly, the proposed formulation is outlined, and then applied to the case of a cantilever edge-cracked nanobeam. A parametric study is performed by varying both the crack depth and the crack position along the beam axis. Finally, the above formulation is applied to simulate some experimental tests available in the literature
The effect of containing Al2O3 microparticles in different matrix polymers on properties of pineapple fiber-reinforced composites
Get PDFIn this study, Al2O3 microparticle was used as a filler for pineapple fiber reinforced composites with different matrix polymers. The effect of Al2O3 microparticles in the epoxy and unsaturated polyester matrix on the mechanical, physical, and thermal properties of pineapple fiber reinforced composites was investigated. Pineapple fiber composite was manufactured by hand layup with various Al2O3 contents, 0, 5, 10, and 15 wt%, and a 30 wt% continuous pineapple fiber. The tensile, flexural strength, hardness, water absorption, and thermal stability were investigated according to ASTM. The results showed that flexural strength, hardness, density, and water resistance gradually increased, and the tensile strength rate gradually decreased with more the wt.% of Al2O3 microparticle. The TGA observation results indicated that the Al2O3 microparticles improved the composite's thermal stability. Composites with the epoxy matrix are superior in tensile strength and thermal stability compared to composites made of unsaturated polyester. In contrast, unsaturated polyester matrix composites had higher flexural strength, hardness, density, and water resistance than epoxy matrix composites. The effect of the content of 15 wt% Al2O3 microparticles in the composites resulted in the highest flexural strength, hardness, density, and water absorption resistance, while the tensile strength showed the lowest value
Experimental studies to evaluate tensile and bond strength of Stainless-Steel Wire Mesh (SSWM)
Get PDFStructural strengthening is vital to improve the load-carrying capacity partially or severely damaged Reinforced Concrete (RC) elements. Fiber Reinforced Polymers (FRPs) are widely used for strengthening purposes. In this study, use of Stainless-Steel Wire Mesh (SSWM) is explored, as FRPs are having limitations like high cost, less fire resistance, and brittle behavior. The experimental studies are conducted to evaluate the mechanical properties of the SSWM, to explore its feasibility as a strengthening material. Three different variants of SSWM i.e., 30×32, 40×32 and 50×34 is considered for the study. SSWM used in present study is a woven mesh made from stainless-steel wires manufactured in India. Important mechanical properties such as tensile strength and bond strength with concrete surface is experimentally evaluated in this study. Response of test specimens are evaluated with respect to ultimate load carrying capacity, corresponding deformations, rupture strain, crack formation and failure propagation. SSWM exhibits a tensile strength of 600-1000 MPa which is comparable to tensile strength of various types of fibers used for strengthening. Based on experimental studies, it is found that SSWM 40×32 performs the better in different aspect, so it can be a good alternative for strengthening of RC elements compared to other FRP materials
Nonlinearity of mechanical behavior of 3D-reinforced composites under compression
No full textModern technological capabilities make it possible to produce 3D spatially-reinforced for polymer composite materials. The tasks of experimental research and analysis of the deformation process of new composite materials for aviation purposes taking into account the nonlinearity of mechanical behavior become actual.
The paper presents an experimental study of the mechanical compression behavior of composite material specimens made of 3D woven carbon fiber preforms using the pressure impregnation technology (Resin Transfer Molding method with a pairwise interlayer reinforcement and a longitudinal layer). Compression mechanical tests were carried out on specimens using a universal system of electromechanical testing Instron 5882 and a system of 3D analysis of displacement and strain fields on the surface. Tests were conducted in accordance with ASTM D 3410 recommendations and using specialized tooling. Consideration of nonlinearity parameter during experimental data processing is proposed. The importance of determining the values of critical deformation in compression as a parameter characterizing the moment of the beginning of fracture is noted. Comparison of carbon fiber composite materials made by the same technology from fibers and binders of different manufacturers has been carried out. The experimental diagrams "stress-strain" and their approximating dependences taking into account the nonlinearity function w are obtained. The type of functions w of the studied materials is defined, the linear approximation of dependence of functions w on deformation is substantiated. Values of strength limits, elastic modulus, nonlinearity coefficient and critical damage were obtained, statistical processing of the obtained results and their analysis were carried out