Impact action on fiber and composite material based on it

2020 ◽  
Vol 6 ◽  
pp. 69-74
Author(s):  
V.V. Kudinov ◽  
◽  
I.K. Krylov ◽  
N.V. Korneeva ◽  
◽  
...  
Keyword(s):  
Composite Material ◽  
Deformation Behavior ◽  
Failure Mechanisms ◽  
Basic Mechanism ◽  
Impact Action ◽  
Uhmwpe Fiber ◽  
Mechanism Of Failure ◽  
First Moment ◽  
The Impact ◽  
Ib Method

The low-velosity impact properties and failure mechanisms of ultra-high molecular weight polyethylene (UHMWPE) fiber (Dyneema®SK-75) and a composite material (CM) based on it with the rigid and flexible matrices were investigated by the “Impact Break” (IB) method. A fundamental difference in deformation behavior and failure mechanisms upon impact on the UHMWPE-fiber and on the CM based on this fiber has been investigated experimentally. It is shown that impact has a little effect on the properties of UHMWPE-fiber, since it is an isotropic material. It has been established that upon impact, the properties of a fiber without a matrix were significantly higher than the properties of CM based on it. Impact action stimulates the interaction between CM components (fibers and matrix). Mechanism of stepwise deformation of anisotropic CM is occurred, which begins from the first moment of impact and ends with the destruction of the CM. A “stairway of deformation” behavior is observed in anisotropic materials. Stepwise deformation is the main form of deformation and the basic mechanism of failure of anisotropic composite materials upon impact.

Real-time cryo-deformation of polypropylene and impact-modified polypropylene in the transmission electron microscope

1993 ◽  
Vol 51 ◽  
pp. 892-893
Author(s):  
Robert C. Cieslinski ◽  
H. Craig Silvis ◽  
Daniel J. Murray
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Failure Mechanisms ◽  
Brittle Transition ◽  
Molded Part ◽  
Transmission Electron ◽  
Solvent Cast ◽  
The Impact ◽  
Annealed Copper ◽  
Dynamic Plane

An understanding of the mechanical behavior polymers in the ductile-brittle transition region will result in materials with improved properties. A technique has been developed that allows the realtime observation of dynamic plane stress failure mechanisms in the transmission electron microscope. With the addition of a cryo-tensile stage, this technique has been extented to -173°C, allowing the observation of deformation during the ductile-brittle transition.The technique makes use of an annealed copper cartridge in which a thin section of bulk polymer specimen is bonded and plastically deformed in tension in the TEM using a screw-driven tensile stage. In contrast to previous deformation studies on solvent-cast films, this technique can examine the frozen-in morphology of a molded part.The deformation behavior of polypropylene and polypropylene impact modified with EPDM (ethylene-propylene diene modified) and PE (polyethylene) rubbers were investigated as function of temperature and the molecular weight of the impact modifier.

scholarly journals Clinching of Thermoplastic Composites and Metals—A Comparison of Three Novel Joining Technologies

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2286
Author(s):  
Benjamin Gröger ◽  
Juliane Troschitz ◽  
Julian Vorderbrüggen ◽  
Christian Vogel ◽  
Robert Kupfer ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Composite Material ◽  
Process Design ◽  
Failure Mechanisms ◽  
Thermoplastic Composites ◽  
Material Structure ◽  
Shear Tests ◽  
Load Bearing ◽  
Lap Shear ◽  
Resultant Material

Clinching continuous fibre reinforced thermoplastic composites and metals is challenging due to the low ductility of the composite material. Therefore, a number of novel clinching technologies has been developed specifically for these material combinations. A systematic overview of these advanced clinching methods is given in the present paper. With a focus on process design, three selected clinching methods suitable for different joining tasks are described in detail. The clinching processes including equipment and tools, observed process phenomena and the resultant material structure are compared. Process phenomena during joining are explained in general and compared using computed tomography and micrograph images for each process. In addition the load bearing behaviour and the corresponding failure mechanisms are investigated by means of single-lap shear tests. Finally, the new joining technologies are discussed regarding application relevant criteria.

Rupture by impact-induced fatigue of a copper foil strip embedded in a multifunctional composite material

2021 ◽  
pp. 002199832199432
Author(s):  
Yacine Ouroua ◽  
Said Abdi ◽  
Imene Bachirbey
Keyword(s):  
Composite Material ◽  
Mechanical Characteristics ◽  
Glass Fibers ◽  
Energy Levels ◽  
Fatigue Tests ◽  
Repeated Impact ◽  
Aeronautical Industry ◽  
Repeated Impacts ◽  
Cracking Mode ◽  
The Impact

Multifunctional composite materials are highly sought-after by the aerospace and aeronautical industry but their performance depends on their ability to sustain various forms of damages, in particular damages due to repeated impacts. In this work we studied the mechanical behavior of a layered glass-epoxy composite with copper inserts subjected to fatigue under repeated impacts with different energy levels. Damage evolution as a function of impact energy was carefully monitored in order to determine the effect of the copper inserts on mechanical characteristics of the multifunctional composite, such as endurance and life. Results of repeated impact tests show that electric current interruption in the copper inserts occurs prior to the total perforation of the composite material, and after about 75% of the total number of impacts to failure. This is the case for the three energy levels considered in this study, [Formula: see text] = 2, 3 and 4 Joules. The epoxy resin was dissolved chemically in order to preserve the mechanical structure of the damaged copper inserts and the composite fibers for further inspection and analysis. Scanning electron microscopy (SEM) of the fractured copper inserts revealed interesting information on the nature of the damage, including information on plastic deformation, strain hardening, cracking mode, temperature increase during the impacts, and most importantly the glass fibers and their roles during the impact-fatigue tests.

Unele aspecte metodologice de studiu a biodiversitatii si productivitatii fitocenozelor din cadrul ecosistemelor urbane

2019 ◽  
Author(s):  
Constantin Bulimaga ◽  
◽  
Anastasia Portarescu ◽  
Keyword(s):  
Riparian Vegetation ◽  
Anthropogenic Activities ◽  
Natural Ecosystems ◽  
Impact Action ◽  
Productive Potential ◽  
Study Methodology ◽  
Biodiversity Study ◽  
The Impact ◽  
The City ◽  
Urban Activities

Anthropogenic activities cause damage to the natural ecosystems in the city in various ways, which contributes to the reduction of biodiversity. Considering that biodiversity is becoming more vulnerable to the impact action triggered by urban activities is necessary to monitor it in order to take urgent measures to protect and preserve it. The plant biodiversity study methodology includes methods that help determine phytocenosis parameters and assess biomass in order to estimate the productive potential of phytocenosis. Carrying out the research according to the proposed methodology will make it possible to assess the anthropogenic impact on the terrestrial and riparian vegetation.

scholarly journals A Short Note about the Impact Action of a Water Jet Stabilized by a Coaxial Air Stream in the Air and Underwater

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5015
Author(s):  
Josef Poláček ◽  
Irena Marie Hlaváčová ◽  
Martin Tyč
Keyword(s):  
Near Field ◽  
Pure Water ◽  
Air Flow ◽  
Relevant Literature ◽  
Short Note ◽  
Original Method ◽  
Water Jet ◽  
Impact Action ◽  
Dual Action ◽  
The Impact

A new original method, applying a coaxial protective airflow, was tested aiming to improve the pure water jet efficiency in surface layer removal or medium hard materials cutting or blasting. The dual action of the air flow is expected: the air co-flowing the water jet with approximately the same velocity should prevent the central jet from breaking up into tiny droplets in the near field, and simultaneously, it should support jet decomposition into big parts with enough destructive potential in the far-field. A brief survey of the relevant literature dealing with the water jet instability is presented, introducing four recognized breakup regimes. An original cutting head designed to generate a waterjet surrounded by protective coaxial air flow is introduced. The submitted device is supposed to operate within the first wind-induced regime. Two types of experiments, consisting of blasting limestone bricks placed either in the air or underwater, were realized. The depths of kerfs produced with different water pressures and air overpressures were evaluated. While no substantial positive effect was recognized in the air performance, the submerged blasting of the same material under similar conditions appeared to be promising.

Enhancement of neuroplasticity by drug therapy

2020 ◽  
pp. 221-236
Author(s):  
Ulf Ziemann
Keyword(s):  
Basic Research ◽  
Long Term Potentiation ◽  
Basic Mechanism ◽  
Human Studies ◽  
Dependent Plasticity ◽  
Open Questions ◽  
Term Potentiation ◽  
Specific Practice ◽  
The Impact ◽  
Activity Dependent

This chapter reviews effects of central nervous system (CNS) active drugs specifically on activity-dependent plasticity and learning. The rationale for choosing this focus is the existing evidence that CNS active drugs have an impact on rehabilitation success after stroke to a relevant extent only if coupled with task-specific practice. This chapter reviews pharmacological modulation of stimulation-induced long-term potentiation (LTP) in animal and human studies because synaptic plasticity in the form of LTP is a basic mechanism of learning and memory processes. Next, the chapter reviews the evidence of CNS active drugs on learning in animal and human studies. In the third part, the impact of CNS active drugs on neurorehabilitation of stroke patients is surveyed and the translational cascade from basic research to clinical studies is described. Finally, limitations of the current studies, open questions, and future directions are discussed. This chapter demonstrates significant impact of neuropharmacology on activity-dependent plasticity and learning.

scholarly journals A Method for Evaluating the Impact Wear Behavior of Multilayer TiN/Ti Coating

Coatings ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 132 ◽  
Author(s):  
Xin Cao ◽  
Weisheng Xu ◽  
Weifeng He
Keyword(s):  
Wear Behavior ◽  
Failure Mechanisms ◽  
High Stress ◽  
Impact Wear ◽  
Maximum Value ◽  
Impact Peak ◽  
Energy Dissipated ◽  
The Impact ◽  
Impact Zones ◽  
Circular Cracks

An energy-controlled cycling impact test was applied to evaluate the impact wear behavior of hard coating. A multilayer TiN/Ti coating with a total thickness of ~10 μm, containing two TiN layers and two Ti layers, with the thickness ratio of these two kinds of the layers being 9:1, was chosen as the research object. The impact velocities were 60, 120, and 180 mm/s, and the impact cycles were 10, 102, 103, and 104, respectively. Damage morphology observation and numerical simulation were used to analyze the failure mechanisms. The results show that the contact time keeps almost constant under different impact velocities and cycles. Impact peak forces remain unchanged with increasing cycles at the same velocity, but they increase linearly with impact velocities, reaching a maximum value of 262.26 N at 180 mm/s. The energy dissipated rate (EDR) increases from 31.58% at 60 mm/s to 35.59% at 180 mm/s, indicating the degenerative toughness. Two impact-wear failure mechanisms are found in impact zones of the coating; these are peeling and circular cracks. Peelings are induced by cycling high-stress gradients in hard layers and interfaces. Circular cracks are caused by cycling tensile stresses in the form of fatigue at the edge of impacted pits.

Effect of Severe Plastic Deformation and Hardening on the Properties and Failure Mechanisms of Constructional Steel

2019 ◽  
Vol 945 ◽  
pp. 579-584
Author(s):  
Maria Z. Borisova
Keyword(s):  
Plastic Deformation ◽  
Impact Strength ◽  
Severe Plastic Deformation ◽  
Structural Steel ◽  
Negative Impact ◽  
Failure Mechanisms ◽  
Positive Influence ◽  
Constructional Steel ◽  
Angular Pressing ◽  
The Impact

The influence of severe plastic deformation on structural materials has been actively studied in recent years. Undoubtedly is the positive influence of this method on strength characteristics of materials. In addition, it is very interesting to influence of the severe plastic deformation on the mechanisms of fracture. One of the most common methods of severe plastic deformation is equal-channel angular pressing (ECAP). In this paper, the influence of different modes of ECAP on the strength of structural steel was studied. Also, the destruction of steel at different test temperatures was studied in detail. It is shown that the ECAP increases the strength of steel almost twice, but the plasticity of steel is reduced, which leads to fragility. Quenching can remove the negative impact of the ECAP on toughness of the steel and will increase the impact strength several times.

scholarly journals The Impact of Lubricant Film Thickness and Ball Bearings Failures

Lubricants ◽  
2019 ◽  
Vol 7 (6) ◽  
pp. 48 ◽  
Author(s):  
Matthew David Marko
Keyword(s):  
Film Thickness ◽  
Fatigue Failure ◽  
Failure Mechanisms ◽  
Roller Bearing ◽  
Lubricant Film ◽  
Theoretical Formula ◽  
Empirical Equations ◽  
Ball Bearings ◽  
Lubricant Film Thickness ◽  
The Impact

An effort was made to find a relationship between the lubricant thickness at the point of contact of rolling element ball bearings, and empirical equations to predict the life for bearings under constant motion. Two independent failure mechanisms were considered, fatigue failure and lubricant failure resulting in seizing of the roller bearing. A theoretical formula for both methods was established for the combined probability of failure using both failure mechanisms. Fatigue failure was modeled with the empirical equations of Lundberg and Palmgren and standardized in DIN/ISO281. The seizure failure, which this effort sought to investigate, was predicted using Greenwood and Williamson’s theories on surface roughness and asperities during lubricated contact. These two mechanisms were combined, and compared to predicted cycle lives of commercial roller bearing, and a clear correlation was demonstrated. This effort demonstrated that the Greenwood–Williams theories on the relative height of asperities versus lubricant film thickness can be used to predict the probability of a lubricant failure resulting in a roller bearing seizing during use.

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