scholarly journals Flexural Pseudo-Ductility Effect in Hybrid GFRP/CFRP Bars under Static Loading Conditions

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5608
Author(s):  
Szymon Duda ◽  
Grzegorz Lesiuk ◽  
Paweł Zielonka ◽  
Paweł Stabla ◽  
Marek Lubecki ◽  
...  
Keyword(s):  
Epoxy Matrix ◽  
Mechanical Test ◽  
Microstructural Analysis ◽  
Filament Winding ◽  
Engineering Industry ◽  
Microstructural Investigation ◽  
Four Point Bending ◽  
Composite Layers ◽  
Fibre Reinforced Polymer ◽  
Glass Frp

The problem with composite rebars in the civil engineering industry is often described as the material’s brittleness while overloaded. To overcome this drawback, researchers pay attention to the pseudo-ductility effect. The paper presents four-point bending tests of pure unidirectional (UD) rods with additional composite layers obtained by filament winding and hand braiding techniques. Two types of core materials, glass FRP (fibre reinforced polymer) and carbon FRP, were used. Regarding the overwrapping material, the filament winding technique utilized carbon and glass roving reinforcement in the epoxy matrix, while in the case of hand braiding, the carbon fibre sleeve was applied with the epoxy matrix. Microstructural analysis using scanning electron microscopy (SEM) and computed tomography (CT) was performed to reveal the structural differences between the two proposed methods. Mechanical test results showed good material behaviour exhibiting the pseudo-ductility effect after the point of maximum force. The two applied overwrapping techniques had different influences on the pseudo-ductility effect. Microstructural investigation revealed differences between the groups of specimens that partially explain their different characters during mechanical testing.

Manufacturing a carbon/epoxy NACA 23018 airfoil skin using a circular braiding machine: experimental and numerical study

2021 ◽  
pp. 152808372199377
Author(s):  
Jalil Hajrasouliha ◽  
Mohammad Sheikhzadeh
Keyword(s):  
Numerical Study ◽  
Filament Winding ◽  
Bending Test ◽  
Elastic Response ◽  
Manufacturing Processes ◽  
Fiber Reinforced Composite ◽  
Four Point Bending ◽  
Reinforced Composite ◽  
Four Point Bending Test ◽  
Meso Scale

In the interest of reducing the weight and also cost of blade skins, various automatic preform manufacturing processes were developed including tape laying, filament winding and braiding. Among them, the circular braiding process was found to be an efficient method in producing seamless preforms on mandrels with various geometries. In this regard, an attempt was made to produce a carbon fiber reinforced composite with the shape of NACA 23018 airfoil using a circular braiding machine. Thus, suitable wooden mandrels were manufactured using NACA 23018 airfoil coordinates, which were obtained by assuming the perimeter of 20 cm. Furthermore, both biaxially and triaxially braided preforms were produced and subsequently impregnated with epoxy resin through an appropriate fabrication method. To assess their performance, four-point bending test was carried out on samples. Ultimately, the elastic response of braided composite airfoils was predicted using a meso-scale finite element modeling and was validated with experimental results.

scholarly journals Determination of tension strength in the longitudinal and circumferentional direction in glass-polyester composite pipes

2009 ◽  
pp. 155-163 ◽  
Author(s):  
Slavisa Putic ◽  
Marina Stamenovic ◽  
Branislav Bajceta ◽  
Dragana Vitkovic
Keyword(s):  
Mechanical Test ◽  
Glass Fibers ◽  
Tension Test ◽  
Filament Winding ◽  
Test Machine ◽  
Process Industries ◽  
Polyester Composite ◽  
Glass Fiber Reinforcement ◽  
Composite Pipes

Polymer composite pipes with glass fiber reinforcement have today a wide usage in the chemical and process industries. The basic subject of this paper is the determination and distribution of stresses and strains in longitudinal and circumferentional directions of glass-polyester pipes under tension test. Also, the tension strengths in both directions are determined out. Tension test was performed on an electro-mechanical test machine on flat samples and rings obtained by cutting of pipes produced by the method 'Filament winding' with glass fibers reinforcement ?55?. Also, the micromechanical analysis on fracture surfaces was done by SEM, which provided the knowledge about models and mechanisms of fracture on applyed loading.

scholarly journals Failure Mechanisms of Sisal Fibres in Composites

1999 ◽  
Vol 8 (1) ◽  
pp. 096369359900800 ◽  
Author(s):  
S. L. Bai ◽  
C. M.L. Wu ◽  
Y.-W. Mai ◽  
H. M. Zeng ◽  
R. K. Y. Li
Keyword(s):  
Epoxy Matrix ◽  
Fibre Bundle ◽  
Failure Mechanisms ◽  
High Strength ◽  
Matrix Interface ◽  
Sisal Fibre ◽  
Bending Tests ◽  
Bonding Material ◽  
Four Point Bending ◽  
Scanning Electron

Model specimens, each containing five embedded continuous sisal fibres in an epoxy matrix, were subjected to four-point bending tests. The micro-failure behaviour of sisal fibres was examined using scanning electron microscopy (SEM). Interfacial debonding of both sisal fibre bundle/epoxy matrix and tubular micro-fibre/bonding material was also noted in all embedded fibres. The fibre bundle/matrix interface had a moderate high strength; but the adhesive strength between the micro-tubular fibre and the bonding material appeared to be small.

Fatigue Strength of Ti-35Nb-7Zr-5Ta

2012 ◽  
Vol 727-728 ◽  
pp. 73-79
Author(s):  
H. Alexander Franco ◽  
Cosme Roberto Moreira Silva ◽  
J.L.A. Ferreira ◽  
José A. Araújo
Keyword(s):  
Fatigue Strength ◽  
Grain Boundaries ◽  
Microstructural Analysis ◽  
Mean Stress ◽  
High Porosity ◽  
High Oxygen Content ◽  
Bending Fatigue ◽  
Four Point Bending ◽  
Ω Phase ◽  
Α Phase

Mean stress on fatigue strength of Ti-35Nb-7Zr-5Ta, used in the manufacture of orthopedic prostheses, was evaluates. Samples of Ti-35Nb-7Zr-5Ta were pressureless, sintered and tested using microhardness (Vickers) and four point bending fatigue conditions. Characterization was carried out using optical microscopy, scanning electron microscopy, EDS analysis, oxygen analysis and density. The microstructural analysis shows low densification after sintering (almost 86% of theoretical) and some precipitates of α phase and presumably ω phase at the grain and grain boundaries. The bending fatigue resistance limit reached (Se (106) = 90 MPa), due to, presumably, the influence of the medium-high porosity, α phase precipitates at grain boundaries as well as the high oxygen content in the material after sintering (0.96 %). In this case, Kwofie model best explains the influence of mean stress on fatigue strength of this alloy.

scholarly journals Flexural Performance of a Hybrid Bridge Deck with Pultruded Fibre Reinforced Polymer Composite Sandwich Panels

2018 ◽  
Vol 13 (3) ◽  
pp. 165-191 ◽  
Author(s):  
Lei Wu ◽  
Yujun Qi ◽  
Weiqing Liu
Keyword(s):  
Working Conditions ◽  
Bridge Deck ◽  
Composite Sandwich ◽  
Four Point Bending ◽  
Reinforced Polymer ◽  
Hybrid Bridge ◽  
Service Load ◽  
Fibre Reinforced Polymer ◽  
Wheel Loading ◽  
Eccentric Wheel

Hybrid bridge decks with the pultruded fibre reinforced polymer have advantageous properties but easily crack because of their unsatisfactory transverse strength and shear strength. This study proposed a type of bridge deck composed of innovative pultruded fibre reinforced polymer composite sandwich panels. Using four-point bending tests, concentric wheelloading tests and eccentric wheel-loading tests combined with first-order shear deformation theory, this study investigated the failure mode, flexural capacity, deformation and ductility of hybrid bridge decks under different working conditions. Under four-point bending and concentric wheel loading, the primary failure modes for this hybrid bridge deck were shear failures along the fibre direction and buckling failure of the upper panel. Under eccentric wheel loading, the primary failure mode was a torsional failure due to the eccentric load. The bearing capacities of the hybrid bridge deck under the three working conditions were 3.8, 3.5 and 3.2 times the service load of a Class I vehicle load, respectively. Besides, the hybrid bridge deck remained in the linear elastic stress state at 2.6 times the service load, indicating that this hybrid bridge deck withstands relatively large vehicle overload without visible damage. The ductility values of this hybrid bridge deck under the three working conditions were 1.79, 2.09 and 2.00, respectively, which are higher than the values for an ordinary pultruded bridge deck. Therefore, the proposed design has the relatively good energy-dissipating capacity, which improves the emergency capacity of the bridge deck.

scholarly journals Effects of Bonded Splice Joints on the Flexural Response of Pultruded Fibre Reinforced Polymer Beams

2010 ◽  
Vol 24-25 ◽  
pp. 401-406 ◽  
Author(s):  
G.J. Turvey
Keyword(s):  
Minor Axis ◽  
Flexural Response ◽  
Four Point Bending ◽  
Reinforced Polymer ◽  
Theoretical Predictions ◽  
Fibre Reinforced Polymer ◽  
Experimental Values

Three Pultruded Fibre Reinforced Polymer (PFRP) 152 x 152 x 6.4mm Wide Flange (WF) beams were fabricated with a central two-plate splice joint. The 6.4mm thick PFRP splice plates were 210, 410 and 610mm long. Each beam was tested in symmetric four-point bending about its major and minor-axis and deflections, rotations and surface strains were recorded. Beam transverse stiffnesses, support rotations and splice rotational stiffnesses were quantified and compared with theoretical predictions. Predicted deflections were 3.5% to 18.5% larger and support rotations were 10% smaller to 14.2% larger than the experimental values. Splice end rotations were generally poorly predicted.

Microstructural characterization of AIN sintered with Y2O3

1988 ◽  
Vol 46 ◽  
pp. 578-579
Author(s):  
S-K. Chiang
Keyword(s):  
Microstructural Analysis ◽  
Microstructural Characterization ◽  
Packaging Material ◽  
Oxygen Impurity ◽  
Microstructural Investigation ◽  
Intergranular Phase ◽  
Processing History ◽  
Triple Points ◽  
Standard Techniques

Aluminum nitride's high thermal but low electrical conductivity make it a potential ceramic packaging material. Processing history, however, can have significant effects on these properties and studies aimed at correlating them to the processing and microstructure are sparse.Pure AIN cannot be readily sintered without additives. Addition of Y2O3 significantly improves its densification behavior and the results presented here concern microstructural analysis of AIN sintered with Y2O3.High-purity AIN powder (containing 1.24% oxygen impurity) with 3 or 9 weight% Y2O3 added was sintered in N2 at 1850°C for 1 hour followed by a further 3 hours at 1900°C. Samples made using this treatment were >95% dense. Specimens for microstructural investigation were prepared using standard techniques and examined using a JEOL 200 CX AEM.The general microstructure of all specimens consists of AIN grains with pockets of intergranular phase(s) located at triple points and some grain boundaries (FIG. 1).

Experimental Study on Structural Rehabilitation of Severely Damaged I-Beams Using Fibre Reinforced Polymers

2021 ◽  
Author(s):  
Jerin Mathew George ◽  
Mehrdad Kimiaei ◽  
Mohamed Elchalakani
Keyword(s):  
Failure Modes ◽  
Offshore Structures ◽  
Reinforced Polymers ◽  
Frp Composites ◽  
Four Point Bending ◽  
Repair Costs ◽  
Structural Rehabilitation ◽  
Carbon Fibre Reinforced Polymers ◽  
Fibre Reinforced Polymer ◽  
Glass Fibre Reinforced

Abstract Fixed and Floating Offshore structures commonly utilize I-beams as structural components withstanding distributed loads on their decks or inside hulls. These structural members get damaged due to the corrosive marine environment leading to a condition in which they need replacement or rehabilitation. Such situations are not desirable as it will incur monetary losses directly with replacement or repair costs and indirectly through operational losses due to shut down for hot repair works. A safe and economical alternative for structural rehabilitation of damaged I-beams is using Fibre Reinforced Polymer (FRP) composites. An experimental investigation on the feasibility of repair of a heavily damaged I-beam using two different types of FRPs is presented. The severe damage in the I-beam was artificially introduced by removing both flanges and the web for 300 mm in the mid-span of 1800 mm long I-beam. Four-point bending tests under static loads were performed until failure of the beam. The first repair was done using carbon fibre reinforced polymers (CFRPs) and the second one utilized glass fibre reinforced polymers (GFRP). The CFRP repaired specimen showed 277% improvement from the damaged state whereas the GFRP repair improved 248% in terms of the ultimate strength. A comparison of the behaviour between CFRP and GFRP repair is also highlighted in the study. Various parameters like stiffness, ductility, load-displacement behaviour and failure modes of these FRP repairs for damaged I-beams are discussed in detail. Overall, the results from the study portray the adequacy of an FRP rehabilitation to reinstate the strength from such structural damages in I-beams.

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