SUB-MICROSCALE SPECKLE PATTERN CREATION ON SINGLE CARBON FIBERS FOR IN-SITU DIC EXPERIMENTS

2021 ◽  
Author(s):  
KARAN SHAH ◽  
GENE YANG ◽  
MOHAMMAD EL LOUBANI ◽  
SUBRAMANI SOCKALINGAM ◽  
DONGKYU LEE
Keyword(s):  
Carbon Fibers ◽  
Fiber Strength ◽  
Glass Fibers ◽  
Speckle Pattern ◽  
Fiber Surface ◽  
Average Diameter ◽  
Sputter Deposition ◽  
Image Correlation ◽  
Longitudinal Tensile Strength ◽  
Fiber Breaks

High performance carbon and glass fibers are widely used as reinforcements in composite material systems for aerospace, automotive, and defense applications. Modifications to fiber surface treatment (sizing) is one of the ways to improve the strength of fibers and hence the overall longitudinal tensile strength of the composite. Single fiber tensile tests at the millimeter scale are typically used to characterize the effect of sizing on fiber strength. However, the characteristic length-scale governing the composite failure due to a cluster of fiber breaks is in the micro-scales. To access such micro-scale gage-lengths, we aim to employ indenters of varying radii to transversely load fibers and use scanning electron microscope (SEM) with digital image correlation (DIC) to measure strains at these lengthscales. The use of DIC technique requires creation of a uniform, random, and high contrast speckle pattern on the fiber surface such as that shown in Figure 1. In this work, we investigate the formation of sub-microscale speckle pattern on carbon fiber surface via sputter deposition and pulsed laser deposition techniques (PLD) using Gold-Palladium (Au-Pd) and Niobium-doped SrTiO3 (Nb:STO) targets respectively. Different processing conditions are investigated for both sputter deposition: sputtering current and coating duration, and PLD: number of pulses respectively to create sub-micron scale patterns viable for micro-DIC on both sized and unsized carbon fibers. By varying the deposition conditions and SEM-imaging the deposited patterns on fibers, successful pattern formation at sub-micron scale is demonstrated for both as-received sized and unsized IM7 carbon fibers of average diameter 5.2 μm via sputter deposition and PLD respectively.

The Tensile Behavior of High-Strength Carbon Fibers

2016 ◽  
Vol 22 (4) ◽  
pp. 841-844 ◽  
Author(s):  
Tye Langston
Keyword(s):  
Young’S Modulus ◽  
Carbon Fibers ◽  
Young's Modulus ◽  
Weak Link ◽  
Fiber Strength ◽  
Fiber Surface ◽  
High Strength ◽  
Carbon Filament ◽  
Specific Strength ◽  
Macro Scale

AbstractCarbon fibers exhibit exceptional properties such as high stiffness and specific strength, making them excellent reinforcements for composite materials. However, it is difficult to directly measure their tensile properties and estimates are often obtained by tensioning fiber bundles or composites. While these macro scale tests are informative for composite design, their results differ from that of direct testing of individual fibers. Furthermore, carbon filament strength also depends on other variables, including the test length, actual fiber diameter, and material flaw distribution. Single fiber tensile testing was performed on high-strength carbon fibers to determine the load and strain at failure. Scanning electron microscopy was also conducted to evaluate the fiber surface morphology and precisely measure each fiber’s diameter. Fiber strength was found to depend on the test gage length and in an effort to better understand the overall expected performance of these fibers at various lengths, statistical weak link scaling was performed. In addition, the true Young’s modulus was also determined by taking the system compliance into account. It was found that all properties (tensile strength, strain to failure, and Young’s modulus) matched very well with the manufacturers’ reported values at 20 mm gage lengths, but deviated significantly at other lengths.

scholarly journals Zero Stress Aging of Glass and Carbon Fibers in Water and Oil—Strength Reduction Explained by Dissolution Kinetics

Fibers ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 107 ◽  
Author(s):  
Andreas T. Echtermeyer ◽  
Andrey E. Krauklis ◽  
Abedin I. Gagani ◽  
Erik Sæter
Keyword(s):  
Carbon Fibers ◽  
Fiber Strength ◽  
Glass Fibers ◽  
Dissolution Kinetics ◽  
Strength Degradation ◽  
Strength Reduction ◽  
Chemical Dissolution ◽  
Structural Applications ◽  
Kinetics Of ◽  
Over Time

Understanding the strength degradation of glass and carbon fibers due to exposure to liquids over time is important for structural applications. A model has been developed for glass fibers that links the strength reduction in water to the increase of the Griffith flaw size of the fibers. The speed of the increase is determined by regular chemical dissolution kinetics of glass in water. Crack growth and strength reduction can be predicted for several water temperatures and pH, based on the corresponding dissolution constants. Agreement with experimental results for the case of water at 60 °C with a pH of 5.8 is reasonably good. Carbon fibers in water and toluene and glass fibers in toluene do not chemically react with the liquid. Subsequently no strength degradation is expected and will be confirmed experimentally. All fiber strength measurements are carried out on bundles. The glass fibers are R-glass.

Research of Interface of Carbon Fiber Reinforced PA6 by In-Situ Anionic Polymerization

2013 ◽  
Vol 634-638 ◽  
pp. 2028-2031
Author(s):  
Hong Kai Zhao ◽  
Li Guang Xiao ◽  
Jing Wu Gao
Keyword(s):  
Heat Treatment ◽  
Composite Material ◽  
Functional Groups ◽  
Carbon Fibers ◽  
Fiber Strength ◽  
Fiber Surface ◽  
Interface Layer ◽  
High Polymer ◽  
Activating Agent

High polymer active functional groups can be grafted on the surface of carbon fibers so as to adjust the interface effect between fibers in the composite material and resin and improve the performance of composite material, by controlling the structure of grafted high polymer, the interface layer with intended performance can be well designed. Heat treatment does not affect the fiber strength, the content of functional groups on the surface of the fibers reaches the max. value around 1h. There are no macromolecules polymerized and grafted on the surface of carbon fibers not subjected to isocyanate grafting treatment. Through isocyanate treatment after heat treatment, it can be obviously seen that the nylon molecules are grafted on the fiber surface. When no activating agent is added in the polymerized monomers, the resin grafting percent of fiber surface can reach 18.8%; when 0.003 activating agent (mole ratio of it to monomers) is added in the monomers, the grafting percent of PA6 on surface of carbon fibers is only 7.65%, this is the result of reactive competition on the interface between monomer matrix and fibers.

scholarly journals A Critical Review on Recycling Composite Waste Using Pyrolysis for Sustainable Development

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5748
Author(s):  
Ramez Abdallah ◽  
Adel Juaidi ◽  
Mahmut A. Savaş ◽  
Hüseyin Çamur ◽  
Aiman Albatayneh ◽  
...  
Keyword(s):  
Carbon Fibers ◽  
Large Scale ◽  
Glass Fibers ◽  
Fiber Surface ◽  
Recycling Process ◽  
Management Options ◽  
Structural Reinforcement ◽  
Recycled Fiber ◽  
And Performance ◽  
Recycled Fibers

The rising usage of carbon and glass fibers has raised awareness of scrap management options. Every year, tons of composite scrap containing precious carbon and glass fibers accumulate from numerous sectors. It is necessary to recycle them efficiently, without harming the environment. Pyrolysis seems to be a realistic and promising approach, not only for efficient recovery, but also for high-quality fiber production. In this paper, the essential characteristics of the pyrolysis process, their influence on fiber characteristics, and the use of recovered fibers in the creation of a new composite are highlighted. Pyrolysis, like any other recycling process, has several drawbacks, the most problematic of which is the probability of char development on the resultant fiber surface. Due to the char, the mechanical characteristics of the recovered fibers may decrease substantially. Chemically treating and post-heating the fibers both help to reduce char formation, but only to a limited degree. Thus, it was important to identify the material cost reductions that may be achieved using recovered carbon fibers as structural reinforcement, as well as the manufacture of high-value products using recycled carbon fibers on a large scale. Recycled fibers are cheaper than virgin fibers, but they inherently vary from them as well. This has hampered the entry of recycled fiber into the virgin fiber industry. Based on cost and performance, the task of the current study was to modify the material in such a way that virgin fiber was replaced with recycled fiber. In order to successfully modify the recycling process, a regulated optimum temperature and residence duration in post-pyrolysis were advantageous.

scholarly journals Sputter Deposited Metal Layers Embedded in Composites—From Fundamentals to Applications

Coatings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 190
Author(s):  
Florian Cougnon ◽  
Mathias Kersemans ◽  
Wim Van Paepegem ◽  
Diederik Depla
Keyword(s):  
Thin Films ◽  
Heat Flux ◽  
Sputter Deposition ◽  
Image Correlation ◽  
Fiber Reinforced Polymers ◽  
Thermal Probe ◽  
Reinforced Polymers ◽  
Magnetron Sputter Deposition ◽  
Sputter Deposited ◽  
Metal Layers

Due to the low heat flux towards the substrate, magnetron sputter deposition offers the possibility to deposit thin films on heat sensitive materials such as fiber-reinforced polymers, also known as composite materials. Passive thermal probe measurements during the sputter deposition of metal layers show indeed that the temperature increase remains well below 25 °C for film thicknesses up to 600 nm. The latter thickness threshold is based on the influence of embedded metal films on the adhesion of the composite plies. Films thicker than this threshold deteriorate the mechanical integrity of the composite. The introduction of the uncured composite in the vacuum chamber strongly affects the base pressure by outgassing of impurities from the composite. The impurities affect the film properties as illustrated by their impact on the Seebeck coefficient of sputter deposited thermocouples. The restrictions to embed thin films in composites, as illustrated by both the heat flux measurements, and the study on the influence of impurities, are however not insurmountable. The possibility to use embedded thin films will be briefly demonstrated in different applications such as digital volume image correlation, thermocouples, and de-icing.

Effects of abrasion on mechanical properties of Kevlar KM2-600 and S glass tows

2018 ◽  
Vol 89 (6) ◽  
pp. 989-1002
Author(s):  
A Abu Obaid ◽  
JW Gillespie
Keyword(s):  
Mechanical Properties ◽  
Abrasion Resistance ◽  
Glass Fibers ◽  
Fiber Surface ◽  
Surface Damage ◽  
Contact Length ◽  
Test Machine ◽  
Tension Level ◽  
Micro Cracks ◽  
Coating Removal

In this effort, the effects of abrasion on the mechanical properties of Kevlar KM2-600 and two types of S glass tows (AGY S2 and Owens Corning Shield Strand S) are studied. Data was generated from cyclic abrasion tests conducted at a tension level of 8% of failure load at10 mm/s (24 in/min) using a specially developed abrasion test machine. Fit curves for axial modulus and tenacity loss were established as a function of abrasion time/contact length for each tow type. Fiber surface damage and fiber breakage within the tows were identified as the major source of tow property degradation. Based on scanning electron microscopy measurements, glass fibers exhibited surface damage (micro-cracks and sizing/coating removal) that were more extensive in AGY S2 glass fibers. Kevlar KM2 fibers after tow abrasion tests exhibited fibrillation and peeling of broken fibrils from the fiber surface. In all three fibers, surface damage increased at longer abrasion times/friction contact length. Overall, the results indicated that the abrasion resistance is the highest for Kevlar KM2, followed by OCV Shield Strand and AGY S2 glass tows. The sizing material on OCV Shield Strand fibers contributed to the improved abrasion resistance compared to AGY S2.

Comparison of Bio and Eco-technologies with Chemical Methods for Pre-treatment of Flax Fibers: Impact on Fiber Properties

2014 ◽  
Vol 9 (4) ◽  
pp. 155892501400900 ◽  
Author(s):  
Sabela Camano ◽  
Nemeshwaree Behary ◽  
Philippe Vroman ◽  
Christine Campagne
Keyword(s):  
Water Absorption ◽  
Fiber Bundle ◽  
Glass Fibers ◽  
Fiber Surface ◽  
Pectate Lyase ◽  
High Water ◽  
Absorption Capacity ◽  
Water Absorption Capacity ◽  
Flax Fibers ◽  
The Impact

Flax fibers, available as fiber bundles, are commonly used as fiber reinforcement in composite materials as a substitute for glass fibers. Pre-treatments are often necessary for improving fiber-resin adhesion, and also to facilitate fiber elementarization, and to improve fiber ability to be implemented in mechanical processes limiting fiber damages. This paper focuses on the impact of biotechnologies (effect of 2 different enzymes: a pectate lyase and a laccase) and of an ecotechnology (ultrasound with ethanol), compared to classical chemical pre-treatments (using aqueous NaOH and ammonia) on the final flax fiber bundle properties, before and after a carding process. Fiber surface properties (wettability and/or zeta potential values), fiber elementarization and mechanical properties vary with the type of treatment (chemical nature of product and conditions used). Fibers elementarised using pectate lyase and ultrasound/ethanol have a hydrophilic surface and a high water absorption capacity, and are also of highest quality in terms of increased fineness. Treatment with NaOH yields the poorest fiber bundle tenacity. Laccase enzyme yields long thick hydrophobic fibers having very low water absorption capacity, and the most neutral surface charge. Properties of flax fibers can be easily monitored using different pre-treatments resulting in fibers which would be suited for various final applications.

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