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1

Porównanie ugięcia betonowych belek zbrojonych prętami GFRP, BFRP i ze stali B500

Pytlowany Tomasz, Leń Dariusz, Piszczek Kazimierz, Zimka Roman

Przegląd Budowlany

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2024

|

R. 95, nr 1-2

77--80

PL

Głównym celem badań było uzyskanie danych związanych z jakościową oceną sztywności belek betonowych zbrojonych prętami stalowymi EPSTAL B500SP oraz kompozytowymi prętami zbrojeniowymi GFRP i BFRP przy zachowaniu tego samego stopnia zbrojenia belek. Przyjęto schemat statyczny badanych elementów w postaci belki swobodnie podpartej o rozpiętości 1,5 m. Podstawowym opisem zachowania badanych elementów, zarejestrowanym podczas badań, była ścieżka równowagi statycznej opisana w układzie współrzędnych: siła obciążająca P i ugięcie belki u, rejestrowane za pomocą czujników, zarejestrowane zależności P-u. Podane na wykresach wartości ugięcia belek u są średnią arytmetyczną pomiarów z czujników przemieszczenia. W trakcie badań wykonano również pomiary odkształceń prętów zbrojeniowych w zależności od wartości przyłożonego obciążenia P. Wyniki tych pomiarów przedstawiono graficznie.

EN

The main purpose of the research was to obtain data related to the qualitative assessment of the stiffness of concrete beams reinforced with B500SP EPSTAL steel reinforcement bars and GFRP and BFRP composite reinforcing bars while maintaining the same degree of reinforcement of the beams. A static scheme of the tested elements was adopted in the form of a simply supported beam with a span of 1,5 m. The basic description of the behavior of the tested elements, recorded during the tests, was the static equilibrium path described in the coordinate system: loading force P and beam deflection u, recorded using sensors, the recorded P-u dependencies. The deflection values of the beams u given in the graphs are the arithmetic mean of the measurements from the displacement sensors. During the tests, measurements of reinforcing bars deformation were also carried out depending on the value of the applied load P. The results of these measurements are presented graphically.

2

Use of computed tomography to assess quality and structure of curved CFRP laminate samples produced by autoclave technology

Helizanowicz Barbara, Helizanowicz Damian, Krzemiński Łukasz, Matula Grzegorz

Composites Theory and Practice

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2024

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R. 24, nr 1

72--77

EN

Carbon fiber reinforced polymer (CFRP) composite laminates are widely used in parts with complex shapes with different curvatures. The curved regions are susceptible to the occurrence of manufacturing defects and premature in-service damage, thus the nondestructive inspection (NDI) of the curved regions is an important issue. X-ray computed tomography (CT) was used to assess the structure of CFRP composite laminate curved beams with different curvature geometry produced in the autoclave technology. The performed inspection allowed visualization of the structure of the curvatures on the ply level and the detection of defects such as foreign objects, voids, resin rich regions, wrinkles and changes in thickness. Also, the quantitative assessment of the defects and distances between the adjacent layers was carried out. The performed investigations show that X-ray CT is an adequate tool to visualize curved CFRP structures.

3

A new model for predicting the axial compression capacity of reinforced concrete cylinders strengthened with CFRP

Guo Guang, Zhou Li, Wang Bangkang

Archives of Civil Engineering

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2024

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Vol. 70, nr 1

389--404

EN

Numerous scholars have identified the shortcomings of imprecise terminology and substantial computational inaccuracies in the current models for predicting the axial compression capacity of CFRPstrengthened reinforced concrete (RC) cylinders. To improve the prediction accuracy of the axial compressive capacity model for CFRP-strengthened RC cylinders, the present axial compressive capacity model for CFRP-strengthened RC cylinders was scrutinized and evaluated. Drawing on Mander’s constraint theory and the concrete triaxial strength model, a novel axial compressive capacity model for CFRP-strengthened RC cylinders was proposed. This study collected 116 experimental data on the axial compression of CFRP-strengthened RC cylinders and analyzed the accuracy of various models using the data. The findings indicate that the model proposed in this study outperforms other models in predicting axial compression capacity and demonstrates high prediction accuracy. Furthermore, an analysis is conducted on the variation law of the model’s predicted value with respect to the design parameters. The proposed model in this study identifies concrete strength, stirrup spacing, and elastic modulus of CFRP as the primary factors that influence the axial compression capacity of CFRP-strengthened RC cylinders.

4

Influence of Size of Open Hole on Stability of Compressed Plate Made of Carbon Fiber Reinforced Polymer

Wysmulski Paweł, Mieczkowski Grzegorz

Advances in Science and Technology. Research Journal

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2024

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Vol. 18, no 2

238--247

EN

This manuscript concerns the investigation of the influence of the open hole on stability of the compression plate made of carbon-epoxy composite. Experimental tests carried out on the real plate resulted in a postcritical path from which the critical load value was determined using appropriate approximation method. In parallel, an independent study was carried out based on a numerical analysis using the finite element method (FEM). Investigations were conducted in terms of a linear eigenproblem analysis, from which the value of the bifurcation load was determined for the FEM model of the plate. Its values resulting from the numerical analyses were validated against the experimental results, thus confirming the adequacy of the designed FEM model of the plate. The paper shows that the incremental increase of the hole in the plate monotonically influences the decrease in the critical load of the plate. The largest decrease was observed for the specimen with the largest hole analysed and was 13.5% compared to a plate without a hole. The newness of the paper is the application of interdisciplinary investigation methods to describe the influence of the open hole compression (OHC) on the stability of composite plates. ABAQUS® was used as the tool with which the numerical analyses were realised.

5

A comparative analysis of single-field concrete slabs reinforced with FRP bars

Piotr Lacki, Niemiro-Maźniak Judyta, Derlatka Anna, Gąćkowski Roman

Zeszyty Naukowe Politechniki Częstochowskiej. Budownictwo

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2023

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Z. 29 (179)

85--91

EN

Fibre-reinforced composite bars (FRP) are becoming an increasingly common alternative to steel reinforcement in civil structures. The paper presents a comparative analysis of single-field concrete slabs reinforced with steel bars and FRP bars. The tested models differed in the type of reinforcement material and the diameter of the reinforcement bars. The behaviour of slab reinforced with steel bars (SRB) and composite bars made of GFRP, CFRP, BFRP and AFRP were simulated. The numerical analysis was carried out in the ADINA System program, based on the Finite Element Method (FEM). The obtained distributions of displacements and the development of cracks in the tested elements made it possible to assess the serviceability limit states (SLS) the slabs. The smallest deflections were observed for slabs reinforced with AFRP bars.

PL

Pręty kompozytowe wzmacniane włóknami (FRP) stają się coraz częstszą alternatywą zbrojenia stalowego w konstrukcjach budowlanych. W pracy przedstawiono analizę porównawczą jednopolowych płyt betonowych zbrojonych prętami stalowymi oraz prętami FRP. Badane modele różniły się rodzajem materiału zbrojenia i średnicą prętów zbrojeniowych. Symulowano zachowanie płyt zbrojonych prętami stalowymi (SRB) i prętami kompozytowymi GFRP, CFRP, BFRP oraz AFRP. Analizę numeryczną przeprowadzono w programie ADINA System, opartym na metodzie elementów skończonych (MES). Uzyskane rozkłady przemieszczeń oraz rozwój zarysowań w badanych elementach pozwoliły na ocenę stanu granicznego użytkowalności płyt. Najmniejsze ugięcia zaobserwowano dla płyt zbrojonych prętami AFRP.

6

Investigations of technical challenges in compounding of recycled carbon fibers

Hannan Azmin, Seidlitz Holger, Krenz Jonas, Müller Marco

Zarządzanie Przedsiębiorstwem

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2023

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Vol. 26, nr 2

7--12

EN

Carbon fiber reinforced plastics (CFRP) owing to its excellent properties have found its extensive application in various fields ranging from medical to automobile and aerospace industries. This has thereby led to ever-increasing demand of carbon fiber production and as well as resulting in tonnes of carbon fiber wastes in the landfills [5]. Due to the high positive impacts of using carbon fibers, the energy intensive and cost intensive production of virgin fibers and the growing landfills are often overlooked. Hence, the need for recycling and repurposing of carbon fiber wastes have gained the significance at present day. Although various recycling technologies have been developed yet, various challenges are faced with processing of recycled carbon fibers (rCF). Besides, the desired application specific properties are not compromised for high cost and high-energy requirement. Therefore, an overall development of processing rCF is sought from not only a sustainability point but also an economic point [7]. Various efficient recycling technologies are currently operating. The challenges arises in commercializing the recycled fibers after the recycling process. The recycled fibers often require various post-processing of fibers and undergoes fiber degradation. This induces a skeptical mindset for the buyers to introduce the recycled fibers in the material ecosystem. This paper currently discusses the processing challenges of long rCF in a compounding plant. To form a closed loop, the recycled fibers are obtained from the novel thermocatalytic degassing process from the CFRP recycling pioneers in Germany, Global EnerTec AG, Guben. This plant in Guben not only recycles carbon fibers from automotive CFRP wastes but also repurposes the epoxy matrices into secondary energy sources. This paper focuses in investigating the processing of rCF obtained from a 100% recycling technology. The aim is to investigate the possible technical challenges so that the rCF can be repurposed to new product manufacturing. Thereby, addressing the concerns with the development of closed loop circular economy in recycling CFRP wastes.

7

Szacowanie nośności belek żelbetowych wzmocnionych kompozytami CFRP

Michałowska-Maziejuk Dorota, Goszczyńska Barbara

Inżynieria i Budownictwo

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2023

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R. 79, nr 11-12

636--643

PL

W artykule przedstawiono propozycję prostego podejścia do szacowania nośności belek żelbetowych wzmocnionych taśmami CFRP, które zostało oparte na wynikach badań eksperymentalnych 10 belek żelbetowych. Badania 2 belek referencyjnych i 8 wzmocnionych taśmami CFRP wklejonymi w betonową otulinę (metoda NSMR) wykonano, symulując rzeczywiste warunki wykonywania wzmocnień. Belki zostały wzmocnione pod obciążeniem w pozycji sufitowej. Wyniki nośności belek uzyskane z badań porównano z wynikami obliczeń na podstawie zaproponowanego podejścia, przyjmując wytrzymałość betonu i stali z badań próbek towarzyszących, a także z normy dla zastosowanej klasy betonu i stali. Porównanie wskazuje na bezpieczne szacowanie nośności.

EN

The article presents a proposal for a simple method of estimating the load-bearing capacity of RC beams strengthened with CFRP strips, based on the results of experimental tests of 10 beams. Tests of two reference beams and eight beams strengthened with CFRP strips glued into the concrete cover (NSMR method) were carried out by simulating the real conditions of strengthening. The beams were strengthened under sustained loading were the strip was applied in the bottom side. The beam load-bearing capacity results obtained from the tests were compared with the calculation results based on the proposed simple method. To estimate the load-bearing capacity, the strength of concrete and steel from the accompanying tests and those provided in the standard regulations was adopted. The comparison indicates a safe estimation of the load capacity.

8

Nośność graniczna próbek wykonanych z betonu samozagęszczalnego układanego wewnątrz rur kompozytowych

Ostrowski Krzysztof Adam, Sikora Oliwia, Furtak Kazimierz

Inżynieria i Budownictwo

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2023

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R. 79, nr 11-12

604--607

PL

W ostatnich latach materiały kompozytowe są szeroko stosowane w celu wzmacniania istniejących konstrukcji, także betonowych. Na ogół proces ten polega na przyklejeniu maty lub taśmy z włókien węglowych (bądź innych) do uprzednio przygotowanej powierzchni betonu, najczęściej przy użyciu żywicy epoksydowej. Wykonywanie konstrukcji betonowych - szczególnie słupów betonowych - wiąże się między innymi z koniecznością wykonania deskowania, systemów rusztowań i późniejszego rozformowania elementu. Proces ten bywa czasochłonny, co wpływa na szybkość wykonania i koszt słupów betonowych. W pracy zaproponowano sposób wykonywania rur kompozytowych z laminatów węglowych oraz ich późniejsze wykorzystanie jako traconą formę do wykonania cylindrycznych próbek zespolonych. Rury kompozytowe o grubości 0,3 i 0,9 mm wypełniono betonem samozagęszczalnym, a następnie poddano badaniom niszczącym w teście jednoosiowego ściskania. Wytrzymałość na ściskanie betonu w osłonie rury o grubości 0,3 mm (SCC-0,3) i 0,9 mm (SCC-0,9) była odpowiednio większa o 37% i 95% w porównaniu z betonem referencyjnym. Średnia wartość maksymalnej odkształcalności osiowej grup próbek wyniosła 0,0048, 0,0069 i 0,0151, odpowiednio dla betonu samozagęszczalnego (SCC), SCC-0,3 i SCC-0,9. Odnotowano także wzrost modułu sprężystości podłużnej betonu wewnątrz rur kompozytowych. Uzyskane wyniki wykazały dobrą współpracę zbrojenia zewnętrznego (rury kompozytowej) z rdzeniem betonowym, pomimo małej przyczepności pomiędzy tymi elementami.

XX

In recent years, composite materials have been widely used to reinforce existing structures, including concrete elements. This process generally consists in gluing a carbon fibers (or other) mat to a previously prepared concrete surface, most often using epoxy resin. Making concrete structures - especially concrete columns - involves the need to make formwork and scaffolding systems and then demolding the elements. This process can be time-consuming, which affects the speed and cost of building a concrete column. This work proposes a method of preparing composite tubes from carbon laminates and their subsequent use as a lost mold for the production of cylindrical composite samples. Composite tubes with an average thickness of 0.3 and 0.9 mm were filled with self-compacting concrete and then subjected to destructive testing in the uniaxial compression test. The compressive strength of the concrete in the 0.3 mm (SCC-0.3) and 0.9 mm (SCC-0.9) pipe sheath was 37% and 95% higher, respectively, compared to the reference concrete. The average value of the maximum axial deformation was 0.0048, 0.0069 and 0.0151 for self-compacting concrete (SCC), SCC-0.3 and SCC-0.9, respectively. An increase in the modulus of elasticity was also noted for the concrete in the composite pipes. The obtained results showed good cooperation of the external reinforcement (composite tube) with the concrete core, despite the infinitesimal adhesion between these elements.

9

Badania nieniszczące materiałów kompozytowych metodą termografii laserowej

Hyla Bartosz, Sobczak Michał, Roemer Jakub

Badania Nieniszczące i Diagnostyka

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2023

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nr 1-4

62--66

PL

Termografia jest jedną z metod badań nieniszczących, która wykorzystuje termowizję do wnioskowania o stanie technicznym materiału. Termografia laserowa jest rodzajem termografii aktywnej w której źródłem wymuszenia jest promieniowanie laserowe. Metoda ta pozwala na bardzo precyzyjne kontrolowanie ilości energii dostarczanej do próbki. Istotną zaletą w badaniach laserowych jest możliwość wykrywania zarówno delaminacji jak i pęknięć będącymi głównymi rodzajami uszkodzeń strukturach kompozytowych. W pracy przedstawione zostanie stanowisko do badań, którego prototyp jest opracowywany na AGH oraz wyniki skanowania na przykładzie próbki z włókna węglowego w osnowie polimerowej.

EN

Thermography is a non-destructive testing method that utilizes infrared camera to infer the technical condition of a material. Laser thermography is a type of active thermography in which laser radiation serves as the excitation source. This method allows for highly precise control of the amount of energy delivered to the sample. An important advantage of laser testing is the capability to detect both delamination and cracks, which are the main types of damage in composite structures. This paper presents a test setup developed at AGH University of Krakow and the results of scanning a sample made of carbon fiber reinforced polymer.

10

Supported by 2D and 3D Imaging Methods Investigation of the Influence of Fiber Orientation on the Mechanical Properties of the Composites Reinforced with Fibers in a Polymer Matrix

Saraczyn Robert, Deroszewska Martyna, Kowaluk Tomasz, Skołek Emilia, Rządkowski Witold, Myszka Dawid

Advances in Science and Technology. Research Journal

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2023

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Vol. 17, no 3

170--183

EN

The aim of this study was to examine the behavior of the carbon fiber reinforced polymer (CFRP) composites depending on the fiber orientation and to understand the influence of microstructural discontinuities on mechanical properties. For the tests 210 gsm prepreg composite and 200 gsm carbon fabric with polymer matrix have been used. Samples were structured and later examined according to the ASTM-D3039 and ASTM-D3878 (equivalents are ISO 20975, ISO 527-4 and ISO 527-5). Accordingly, to the number of layers, three ways of the fibers arranging in relation to the applied force were used. Mechanical properties were determined in a static tensile test. The results of imaging studies, which included analyzes of Digital Image Correlation, Computed Tomography and Scanning Electron Microscopy, showed structural discontinuities, specific stress distribution and propagation of stresses depending on the production technology, which were correlated with the obtained strength results. The source of the gradual development of the degradation of the composite structure was observed in local microdamages and microcracks. As a result of a sub-critical crack growth within the resin matrix material, the defects are subject to a complex, multi-axial stress field on the micro-scale, even if the globally applied force is axial. Samples in which the load was applied along the axis of the fibers behave like an elastic material, while samples, where the force is applied at an angle to the axis of the fibers, tend to behave like an elastic-plastic material.

11

Carbon Fibre Reinforced Polymer Fatigue Strengthening of Old Steel Material

Kowal Maciej, Pietras Daniel

Advances in Science and Technology. Research Journal

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2023

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Vol. 17, no 1

197--209

EN

This paper reports the experimental results of a study investigating the effect of CFRP strengthening of metallic structures for increasing fatigue life. In the study, samples made form puddled steel and mild S235 grade steel strengthened with CFRP strips were examined. Samples were subjected to tensile fatigue loading with a stress ratio R of 0.115 and 0.130 (mild steel samples) and 0.13/1.25/0.15/1.07 (puddled steel samples). A total of 9 samples with CFRP/steel single overlap joints and 20 reference specimens were tested to determine their fatigue life and failure modes. Normal modulus CFRP strips with one cross section (20 x 1.4 mm) were used in this study. Laboratory test results showed that CFRP strengthening has visible effect on the fatigue life of the steel. The application of adhesively bonded CFRP laminates significantly prolongs fatigue life of the specimens. The increase in fatigue life of the steel samples strengthened with CFRP strips was 2 to 16 times (for mild steel) and 11.6 to 34.8 times (for puddled steel).

12

Carbon fiber reinforced polymer and tensegrity structures in search of model architectural and engineering solutions

Franta Anna, Zając Dawid

Technical Transactions

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2022

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Vol. 119, iss. 1

art. no. e2022013

EN

The current era of nanomaterials brings advancements in science and technology. This creates new solutions and possibilities in the creation of novel spatial structures. This study leads through the presentation of iconic architectural objects created with the use of high strength composite materials and tensegrity structure. Then presents the design process, numerical simulations of the three-way tensegrity grid prototype module. Static stress simulations were done within the simulation engine of the Fusion 360 software. Moreover, 1:1 scale prototype was developed. It could be used as a modular construction slab of a novel architectural design. One of the key characteristic features of high strength composite materials, high strength-to-weight ratio, combined with tensegrity structures allows to develop lightweight and hence very durable spatial structures. This gives tensegrity structures a very low dead load value as compared to traditional reinforced concrete structures. Thanks to the application of high strength and hence lightweight materials, the dead load of the prototype is only 0,18 kN/m².

13

Przegląd metod wzmacniania konstrukcji żelbetowych przy użyciu materiałów kompozytowych

Kotynia Renata

Inżynieria i Budownictwo

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2022

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R. 78, nr 11-12

503--515

PL

W pracy przedstawiono sposoby wzmacniania elementów żelbetowych przy użyciu biernych i czynnych systemów wzmacniania materiałami z włóknami węglowymi CFRP przyklejanymi na powierzchni betonu lub wklejanymi w betonowe bruzdy. Omówiono zagadnienia wzmocnień dotyczące zginania i ścinania sposobem biernym oraz czynne systemy wzmocnień. Zaprezentowano wyniki badań własnych prowadzonych w Katedrze Budownictwa Betonowego PŁ w zakresie wzmocnień na zginanie metodami EBR oraz NSMR przy użyciu biernych i czynnych technik. Dodatkowo przedstawiono wyniki badań własnych wzmocnień na ścinanie przy użyciu taśm i mat przyklejanych na zewnętrznej powierzchni oraz taśm wklejanych metodą NSMR.

EN

The paper presents strengthening methods of reinforced concrete elements using passive and active strengthening systems with CFRP carbon fibre materials bonded on the concrete surface or embedded in concrete grooves. The issues of passive and active flexural and shear strengthening have been discussed. The results of own research, carried out at the Department of Concrete Structures, have been presented in the field of flexural strengthening by EBR and NSMR methods, using both passive and active techniques. Additionally, the results of the own research on shear strengthening using strips bonded on the surface using the NSMR method have been presented.

14

Static and dynamic impact performance optimization of CFRP/Al bolt joint coupling structure-lay-up-connection parameters

Xu Wenchao, Wang Dengfeng

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 3

art. no. e118

EN

Static shearing, drawing, and dynamic impact test schemes of carbon fber reinforced polymer (CFRP)/aluminum alloy (Al) bolt joint were designed. The fnite element model of the CFRP/Al bolt joint was established, and the failure modes of the joints under the static and dynamic impact conditions were analyzed. The structure, lay-up, and connection parameters of the joint were defned as design variables, and the static and dynamic impact performance indicators of the joint and the lay-up numbers of the CFRP sheet were defned as optimization objectives. Integrated multiobjective optimization was conducted for joints, employing the radial basis function neural network (RBFNN) surrogate model, elitist nondominated sorting genetic (NSGA-II) algorithm, and entropy-technique for order preference by similarity to ideal solution (E-TOPSIS) decision method. The best trade-of solution was obtained, and the optimal design variables were determined. The optimized joint was fabricated, and static and dynamic impact tests were carried out. The test and simulation results were compared to verify the efectiveness of simulation and optimization.

15

Flexural response of FRP‑strengthened lightweight RC beams: hybrid bond efficiency of L-shape ribbed bars and NSM technique

Tahmouresi Behzad, Momeninejad Kasra, Mohseni Ehsan

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 2

art. no. e95, 1--16

EN

This paper presents the results of an experimental study on employing near surface mounted (NSM) fiber-reinforced polymer (FRP) reinforcement technique, and L-shape ribbed bars, for flexural strengthening of lightweight reinforced concrete (RC) beams. 18 RC beams including 14 lightweight RC beams and four normal-weight concrete beams were designed. The beams were strengthened with glass fiber-reinforced polymer (GFRP) bars and carbon fiber-reinforced polymer (CFRP) laminate in bending tests. Test parameters included: (1) different FRP materials (glass bars and carbon sheets), (2) longitudinal steel reinforcement ratio, and (3) type of strengthening technique used (NSM reinforcement or hybrid). The ultimate tensile strength, deflection, compressive and tensile strain of concrete, and failure mode of the beams were examined under four-point flexural test. Results showed that the ultimate strength of all RC beams increased between 33 and 105% compared to the control beam. The ultimate strength of beams reinforced with CFRP in the mid-span region was 10% higher than that of beams strengthened at both ends, although the former exhibited 28% lower ultimate deflection. The ultimate strength and deflection of RC beams strengthened with combined steel reinforcing bars and GFRP bars were 10% and 108% higher, respectively, compared to those of RC beams strengthened with GFRP bars only. Hybrid L-shape ribbed bars beams showed a considerably higher ductility (up to 170% increase in the ultimate deflection) compared to other beams. The comparison of the experimental results of the ultimate strength of the beams with ACI440-2R guidelines indicated a reasonable and conservative prediction of the code expression.

16

Dimethicone-assisted laser cutting of CFRP hole

Chen Xinghua, Li Wenyuan, Rong Youmin, Zhang Guojun, Chen Long, Huang Yu

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 4

art. no. e182, 2022

EN

When cutting carbon fiber reinforced polymer (CFRP) plate with UV nanosecond laser, the surface heat-affected zone (HAZ) such as fiber exposure and carbonization will occur, which affects the surface morphology and properties of CFRP. In this paper, dimethicone-assisted laser cutting technology is proposed. Compared with laser direct cutting, we found that dimethicone-assisted cutting has obvious advantages in cutting CFRP. Due to the heat transfer inhibition of dimethicone, there is almost no burning phenomenon of matrix materials. The orthogonal test method was used to study the three key process parameters (laser scanning speed, repetition frequency and concentric circle spacing) of dimethicone-assisted laser cutting CFRP. It is concluded that the HAZ width can be controlled at 38.70–54.77 μm with dimethicone, compared with the traditional direct machining (HAZ width: 109.64–439.13 μm). Under the optimal cutting parameters of laser scanning speed of 500 mm/s, repetition rate of 50 kHz and concentric circle spacing of 0.04 mm, the minimum HAZ is 38.70 μm, which is reduced by 85.89% (the HAZ width of laser direct machining is 274.37 μm).

17

Flexure Behavior of Carbon Fiber Reinforced Polymers Retrofitted RC Beams

Fahim Muhammad, Saeed Muhammad, Khan Haris, Gir Alam, Ullah Shahid

Advances in Science and Technology. Research Journal

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2022

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Vol. 16, no 2

188--195

EN

Carbon fiber reinforced polymers (CFRP) have been widely used for retrofitting of reinforced concrete members over the past three decades. This study presents the experimental results of four reinforced concrete beams retrofitted with CFRP and tested under four point monotonic loading. CFRP strips (Sika Carbo-Dur S812) and wraps (Sika-Wrap 230C) were used in two different patterns to evaluate their effect on the flexural behavior of RC beams. Two beams were first tested until their ultimate capacity, retrofitted with the application of CFRP and re-tested again, and two beams were retrofitted before the application of any load. The CFRP strips provided in the middle one-third of the span with U-shaped anchorage at the ends enhanced the capacity of beams up to 15 percent. The stiffness of the beams were significantly increased as demonstrated by smaller displacement at the ultimate load. However, the CFRP wraps provided without the anchorage didn’t enhance the strength due to pre-mature debonding.

18

Cutting Forces and 3D Surface Analysis of CFRP Milling

Biruk-Urban Katarzyna, Józwik Jerzy, Bere Paul

Advances in Science and Technology. Research Journal

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2022

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Vol. 16, no 2

206--215

EN

Due to the wide application of Carbon Fiber Reinforced Polymer (CFRP) composites in various industries, more and more attention is paid to machining these materials. One of the most popular way of machining composites is the milling. Milling of composite materials (CM) is a difficult technology due to their anisotropic and heterogeneous structure and the fact that the reinforcing fibers have an intense abrasive effect on the tool edge during machining. The appropriate selection of technological cutting parameters as well as the type and geometry of the tool can significantly affect the value of cutting forces during milling and the quality of the surface after machining. The aim of the paper is to assess the influence of used tools (differing in the number of cutting edges) and various technological parameters of surface milling of CFRP composites on the cutting forces occurring during machining and on the surface quality after machining. Cutting forces were measured during the milling process on a special stand produced by Kistler and the roughness measurements and surface structure were analyzed using the Alicona InfiniteFocusG5 3D optical microscope. On the basis of performed research it was found that 14 edge tool gives lower values of Fx and Fy components of the cutting forces comparing to 2 edge tool, which is especially noticeable at higher cutting speed values vc=160 m/min, where the values of Fx and Fy components decreased by about 43% at fz=0.0030 mm/tooth. This tool gives also lower values of the Sa roughness parameter 1.65 µm.

19

Young’s modulus of a carbon-reinforced composite at an elevated temperature

Szczepaniak Robert, Przybyłek Paweł, Komorek Andrzej, Sapiński Przemysław, Rowicki Artur, Tkaczuk Sławomir, Rypulak Andrzej, Stabryn Sebastian

Technologia i Automatyzacja Montażu

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2021

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nr 4

29--33

PL

Konstrukcje lotnicze są eksploatowane w zmiennych warunkach środowiskowych wpływających na właściwości kompozytów polimerowych, z jakich często wykonywane są elementy samolotów i śmigłowców. Jednym z takich czynników jest temperatura użytkowania, zmieniająca się podczas lotu w bardzo szerokim zakresie. W artykule zaprezentowano wpływ temperatury eksploatacji na właściwości kompozytu wyznaczane podczas próby rozciągania. Dodatkowo kompozyty przeznaczone do badań wygrzewano w trakcie przygotowania w różnych temperaturach (zgodnie z zaleceniami producenta żywicy będącej osnową). Kompozyty składały się z 7 warstw tkaniny węglowej przesyconych żywicą epoksydową L285 z utwardzaczem. W wyniku badań zauważono, że zmiana temperatury eksploatacji wywiera istotny wpływ na właściwości wytrzymałościowe kompozytu bez względu na temperaturę wygrzewania. Materiały wygrzewane w wyższych temperaturach cechowała większa wartość współczynnika sprężystości wzdłużnej i wytrzymałości na rozciąganie.

EN

Aviation structures are operated under varying environmental conditions, affecting the properties of polymer composites, which are often used to manufacture components for airplanes and helicopters. One of such factors is an operating temperature that changes during a flight in a very wide range. This paper presents the influence of an operating temperature upon composite properties determined during a tensile test. In addition, composites which are intended for the research were post cured during their preparation at different temperatures (in accordance with the recommendations of the resin manufacturer which constitutes a matrix base). The composites consisted of 7 layers of carbon fabric, and matrix of L285 epoxy resin, with a hardener. As a result of the testing it was noted that a change in the operating temperature exerts a significant effect on composite strength properties regardless of the post curing temperature. The materials post cured at higher temperatures were characterized by a greater value of the modulus of elasticity and tensile strength.

20

Numerical investigation and cost analysis of FRP concrete unidirectional hybrid slabs

Mahboob Amir, Eskenati Amir Reza, Moradalizadeh Soheil

International Journal of Applied Mechanics and Engineering

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2021

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Vol. 26, no. 4

156--166

EN

Fiber-reinforced polymer (FRP) has been commonly used to reinforce concrete structures. The kinds of FRP demonstrate an effective alternative to various methods of reinforcement in concrete structures subjected to bad environmental conditions which cause corrosion and damage to concrete. Due to their lightweight, high strength, and high corrosion and fatigue resistance, Fiber Reinforced Polymer (FRP) composites have been widely applied in steel substitution during revitalization interventions. This paper presents numerical three-points bending tests on different models to investigate the effect of the reinforcements; Carbon, Glass, and Aramid fibers to find the corresponding cost of each one. Also, there is an available experimental model for verifying the results of the FEM that demonstrated broad agreement with the experimental statement, concerning the load-displacement curve. After validating the models, alternative designs such as type of the FRP, position of the FRP, and amount of the FRP usage were numerically tested to study the influence of each on the load-bearing capacity. The results showed that the best configuration would be one with GFRP and the load-bearing capacity is around 9kN in the optimum design.