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1

Anti‑impact and vibration‑damping design of cork‑based sandwich structures for low‑speed aerial vehicles

Sheikhi Mohammad Rauf, Gürgen Selim, Altuntas Onder, Sofuoğlu Mehmet Alper

Archives of Civil and Mechanical Engineering

|

2023

|

Vol. 23, no. 2

art. no. e71, 2023

EN

Nowadays, lightweight and eco-friendly composites with improved mechanical properties are highly interesting. Sandwich-structured composites are a type of high-performance structural composite that is lightweight with a high strength-to-weight ratio and excellent specifc energy absorption capabilities. In this study, cork-based sandwich structures resistant to impact and vibrations were designed and produced for the possibility of being used in the protective structures of low-speed aerial vehicles. To identify and match the best combination of different face sheets with a cork core, first, aramid fabric-reinforced polymer (AFRP), carbon fiber-reinforced polymer (CFRP), and glass fiber-reinforced polymer (GFRP) face-sheet composites were produced using the compression molding method (prepreg layup). Then, sandwich structures consisting of AFRP, CFRP, GFRP, and aluminum face sheets with a fixed core layer of cork were designed and assembled. Since the design goal of these structures is to use them in low-speed aerial vehicles, impact deceleration and vibration tests were applied to face sheets and sandwich structures individually, which are the most important factors involved in these structures during fight, particularly in rotary-wing drone applications. A low-energy drop-tower system was used for the calculation of deceleration results. Besides, the vibration properties of the structures were investigated using the modal analysis method and based on the natural frequency responses of the tested face sheets and sandwich structures, damping ratios and structural stiffness were measured. According to the results, compared to other face sheets, CFRP showed better resistance along with the cork core, when the structure was exposed to impact and vibration threats. This study provides useful information on cork core sandwich structures for academic and industrial researchers in choosing the right face sheet.

2

Strength calculations of the Formula 1 car survival cell

Barca Iga

Technologia i Automatyzacja Montażu

|

2022

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nr 1

3--13

EN

The paper presents the results of calculations by the finite element method (FEM) of the monocoque survival cell of a Formula 1 car designed with the use of a sandwich structure in accordance with the Formula 1 Technical Regulations of 2020. The guidelines for the chamber geometry and the necessary certification tests were presented. Proposed solutions in the field of materials for the design of sandwich panels, including cladding made of carbon fiber reinforced laminates and honeycomb cores made of aluminum and titanium. The results of computer simulations were discussed. The analysis of the obtained results of numerical calculations shows that the height of the cell filler has the greatest impact on the strength of the analyzed structure.

PL

W pracy przedstawiono wyniki obliczeń metodą elementów skończonych (MES) komory przetrwania typu monocoque bolidu Formuły 1 projektowanej z wykorzystaniem struktury przekładkowej zgodnie z Regulaminem Technicznym Formuły 1 z 2020 roku. Przedstawiono wytyczne dotyczące geometrii komory oraz niezbędnych testów certyfikacyjnych. Zaproponowano rozwiązania w zakresie materiałów do projektowania płyt przekładkowych, w tym okładzin wykonanych z laminatów wzmacnianych włóknem węglowym oraz rdzeni typu honeycomb przygotowanych z aluminium i tytanu. Omówiono wyniki symulacji komputerowych, uwzględniając również koszty przyjętych rozwiązań. Analiza otrzymanych wyników obliczeń numerycznych wskazuje, że największy wpływ na wytrzymałość analizowanej struktury ma wysokość wypełniacza komórkowego.

3

Comparison of the Bending Resistance Properties of Carbon Fiber/Foam Sandwich Structural Composites with Different Laying Angles

Zhu Lvtao, Cao Shengbin, Zhang Xiaofeng, Shen Wei, Zhu Chengyan

Fibres & Textiles in Eastern Europe

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2022

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Vol. 30, no. 2

75--81

EN

This research aimed to explore the influence of fiber laying angles on the bending resistance properties of carbon fiber/foam sandwich structural composites. Four kinds of composites with the following laying angles: [0°]8, [0°/45°/90°/-45°]s, [0°/90°]4 and [45°/-45°]4 were prepared and tested in three-point bending experiments. The results obtained showed that the bending resistance performance was the best when the laying angle was [0°]8, while it was the worst when the laying angle was [45°/-45°]4. Besides, it was found that the tensile performance was the best when the fibers were arranged in the 0° direction when the strength utilisation rate was the highest. In addition, by observing the failure morphologies of the composites, the delamination and foam cracking were found in the four groups of composites. In contrast, the phenomenon of significant fracture was found on composites with a laying angle of [45°/-45°]4 only, indicating it had a poor bending resistance performance.

4

Effect of Machining Settings and Tool Geometry on Surface Quality After Machining of Al/CFRP Sandwich Structures

Doluk Elżbieta, Rudawska Anna

Advances in Science and Technology. Research Journal

|

2022

|

Vol. 16, no 3

22--33

EN

The paper describes the effect of cutting parameters and tool geometry on the surface quality after machining of an Al/CFRP (aluminium alloy/ Carbon Fibre Reinforced Plastics) sandwich structure. A two-layer sandwich structure made of an EN AW 2024 aluminium alloy and Carbon Fibre Reinforced Plastics (CFRP) was examined. The experiment used the process of peripheral milling. The experiment investigated the effects of cutting speed (vc), feed per blade (fz) and helix angle (λs) on surface quality as defined by differences in the height of materials. It was also analysed how the machining conditions described above affected the values of cutting force components. In the experimental stage of the study, uncoated, double-bit carbide mill cutters with working diameter Dc = 12mm and a variable helix angle (λs = 20˚, λs = 35˚, λs = 45˚) were used. The results have shown that cutting parameters and tool geometry do affect the surface quality and cutting forces after milling of the sandwich structure. The lowest material height difference was achieved when machining with the helix angle λs = 45˚, cutting speed vc = 300m/min and feed per blade fz = 0.08mm/blade. The highest material height difference occurred after machining under the following conditions: vc = 300m/min, fz = 0.08mm/min, λs = 20˚. The minimum cutting force value was obtained for cutting parameters: vc = 80m/min, fz = 0.08mm/blade during milling with the helix angle λs = 45˚. The maximum cutting force was recorded during machining with the helix angle λs = 20˚, cutting speed vc = 400m/min and feed per blade fz = 0.08 mm/blade.

5

Barrier Properties of Footwear Packages against Water Vapour Transport and Thermal Resistance

Serweta Wioleta, Wójcik Justyna, Matusiak Małgorzata

Fibres & Textiles in Eastern Europe

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2021

|

Vol. 29, no. 1 (145)

70--74

EN

In this paper the authors focused on the analysis of relations between the material (such as knitted fabrics with a two and three dimensional structure) configurations and hygienic parameters of packages. In order to measure hygienic properties, the water vapour permeability and absorption were both used with the thermal resistance capacity. The connector role in the packages measured was played by air (in the case of two – layered package), polyurethane foam and three – dimensional knitted fabric with similar characteristics to polyurethane foam in respect of the mass per square metre and thickness. On the basis of the results obtained, a statistical model of the barrier was created and the changes in water vapour transport process described.

PL

W pracy autorzy skoncentrowali się na zbadaniu związków między konfiguracją materiałów takich, jak dzianiny o strukturze płaskiej i przestrzennej, a parametrami higienicznymi powstałych na ich bazie pakietów. Parametry te opisane są poprzez wartości przepuszczalności i absorpcji pary wodnej oraz oporu cieplnego. W roli konektorów oddzielających warstwy materiałowe zastosowano powietrze (w przypadku materiału dwuwarstwowego), recyklingową piankę poliuretanową oraz dzianinę dystansową o masie powierzchniowej i grubości najbardziej zbliżonej do materiału piankowego. Doboru materiałów, będących elementami konstrukcyjnymi pakietów, dokonano na podstawie wcześniejszych prac badawczych nad stworzeniem wewnętrznej bazy materiałów o wysokich właściwościach higienicznych, umożliwiających opracowanie innowacyjnych układów materiałowych przeznaczonych do konstruowania obuwia o podwyższonych walorach higienicznych. Na podstawie uzyskanych wyników badań przepuszczalności pary wodnej stworzono statystyczny model bariery tekstylnej i tworzywowej, a także przeanalizowano zachodzące zmiany jakościowe w procesie transportu pary wodnej. Dodatkowo – zbadano wpływ barier na wartości zastępczego oporu cieplnego dla układów materiałowych. W obu przypadkach – zarówno w odniesieniu do przepuszczalności pary wodnej, jak i uzyskanych wartości oporu cieplnego – stwierdzono różnice istotne statystycznie. W przypadku przepuszczalności pary wodnej, dla zadanego układu materiał – bariera – materiał zaproponowano również model regresyjny. Zaobserwowano spadek dopasowania modelu regresji wraz ze wzrostem ilości i jakości zastosowanej bariery. Świadczy to o wysokiej wrażliwości zjawiska dyfuzyjności na parametry strukturalne zastosowanych barier. Zaproponowane rozwiązanie stanowi obraz możliwych udoskonaleń na etapie projektowania i wytwarzania obuwia o podwyższonych właściwościach higienicznych.

6

Thermal and acoustic behavior of energy saving wall panel

Khan M. Yasir, Baqi Abdul, Sadique Rehan

Archives of Civil Engineering

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2021

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Vol. 67, nr 4

303--316

EN

Research and development of energy-efficient materials have been essential for sustainable infrastructure growth. A considerable amount of money is being spent on various energy stabilization techniques worldwide to attain thermal comfort in buildings. Thus, lowering the energy demand through green materials is vital to save energy and the environment. In this paper, a new form of Structural Insulated Panel (SIP) has been developed and referred to as Ferro Cellular Lightweight Concrete Insulated Panel (FCIP). Comparative thermal efficiency and acoustic performance of FCIP and brick masonry walls have been tested experimentally. The thermal results show that FCIP allows just 2ºC rise in the internal temperature of the room chamber in two hours, whereas the brick masonry allows 9.5ºC rise in the internal temperature of the room chamber for the same period. Similarly, the acoustic results show that FCIP has 0.85 sound absorption coefficient compared to 0.2 for brick masonry wall. Further, the cost-benefit analysis was conducted based on the electricity consumption results of a building produced by the eQuest energy simulation program. The outcome shows that the building’s lifetime running cost gets reduced to 50% when FCIP replaces the concrete/brick masonry envelope.

7

Validation process for computational model of full-scale segment for design of composite footbridge

Ferenc Tomasz, Mikulski Tomasz

Polish Maritime Research

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2020

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nr 2

158--167

EN

Experimental tests and numerical simulations of a full-scale segment of a foot and cycle bridge made of polimer composites are presented in the paper. The analysed structure is made of sandwich panels, which consist of glass fibre reinforced polymer (GFRP) multi-layered laminate faces and a PET foam (obtained from recycling) core. The dimensions of the segment cross-section are the same as for the target footbridge; however, span length was reduced to 3 m. The experimental tests were conducted in a laboratory of the Faculty of Ocean Engineering and Ship Technology at Gdansk University of Technology. A single vertical force was generated by a hydraulic cylinder and was applied to the platform of the structure. The experimental tests were supported by numerical analyses performed in Femap with NX Nastran software by means of the finite element method (FEM). Results obtained in the computational model were compared with results from experiments. Thus, the numerical model was validated and the obtained conclusions were used in the next step of the design process of a composite footbridge with a span length of 14.5 m.

8

Influence of Honeycomb Core Stabilization on Composite Sandwich Structure Geometry

Michalski Mateusz, Krauze Wojciech

Transactions on Aerospace Research

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2019

|

Nr 3 (256)

1--13

EN

Authors showed the influence of stabilization of the honeycomb core on shape of the composite sandwich test panel. Adhesive film laid on core ramps and cured with suitable cure cycle served as core stabilizer. Test panel geometry included different ramp angles (20° and 30°). To verify stabilization process a technology trial was performed. Three test panels were manufactured (3-stage, 1-stage and 1-stage with stabilized core). All test panels were manufactured in OoA process (Out of Autoclave). Panel surfaces were scanned with 3D scanner and compared with the reference CAD model. Both outer skin and inner skin were manufactured in Automated Fiber Placement Laboratory of Warsaw Institute of Aviation.

PL

W artykule przedstawiono wpływ stabilizacji wypełniacza komórkowego na kształt utwardzonej części kompozytowej w postaci przekładkowego panelu testowego o różnych kątach pochylenia ramp (20° oraz 30°). Jako stabilizator wypełniacza posłużył klej błonkowy położony na rampach wypełniacza i następnie utwardzony w odpowiednim cyklu termicznym. Po przeprowadzeniu pozytywnej próby technologicznej stabilizacji wypełniacza zostały wykonane 3 panele w różnych technologiach (1 oraz 3 etapowym). Panel ze stabilizowanym wypełniaczem został utwardzony w procesie 1 etapowym. Wszystkie panele wytworzone zostały w procesie bez użycia autoklawu (OOA – Out of Autoclave). Porównaniu metodą skanowania 3D została poddana powierzchnia wynikowa paneli po utwardzeniu. Jako referencję do porównania został przyjęty model CAD panelu. Zarówno warstwa zewnętrzna jak i wewnętrzna zostały ułożone w Laboratorium Zrobotyzowanego Układania Taśm Kompozytowych Instytutu Lotnictwa za pomocą robota AFP (Automated Fiber Placement).

9

On the modeling of periodic sandwich structures with the use of the broken line hypothesis

Marczak J.

Mechanics and Mechanical Engineering

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2018

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Vol. 22, nr 3

761--773

EN

In this paper a dynamic analysis of sandwich plate with a certain periodic microstructure is considered. The initial system of governing equations is derived basing on the classic broken line hypothesis. As a result of transformations one can obtain a system of three differential equations of motion with periodic, highly oscillating and non-continuous coefficients. In order to derive a system of equations with constant coefficients tolerance averaging technique is applied. Eventually, in the calculation example a free vibration analysis of certain periodic plate strip is performed with the use of both the derived model and a FEM model. It can be observed that the consistency of obtained results is highly dependent on the calculation assumptions.

10

Deflection and strength of a sandwich beam with thin binding layers between faces and a core

Magnucki K., Smyczyński M., Jasion P.

Archives of Mechanics

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2013

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Vol. 65, nr 4

301–-311

EN

The subject of the paper is the analysis of deflection of a five-layer sandwich beam under bending. The mechanical and physical properties vary through the thickness of the beam and depend on the material of each layer, which are: the metal face, binding material (the glue) and metal foam core. The main aim of the paper is to present the analytical model of the five-layer beam and to compare the results of bending analysis obtained theoretically and numerically. In the paper, a mathematical model of the field of displacements, which includes a shear effect and a bending moment, is presented. The system of partial differential equations of equilibrium for the five-layer sandwich beam is derived on the basis of the principle of stationary total potential energy. The equations are analytically solved and the formula describing the deflection of the beam is obtained. The influence of the thickness and mechanical properties of the binding layer on the deflection of the beam under bending is analysed. The comparison of the results obtained in the analytical and numerical (FEM) analysis is shown in graphs and figures.

11

Giant magneto-impedance In amorphous metal lic CO-rich alloys and Sandwich structures

Manko D.Yu.

Pomiary, Automatyka, Komputery w Gospodarce i Ochronie Środowiska

|

2010

|

nr 4

5-7

EN

Giant magneto-impedance in sandwich structures based on Co80-xNixB20 amorphous metallic alloys (x=4,6,8,10,12 at.%) is investigated for alternating current with frequency varied from 1 to 3000 kHz at applied magnetic field. The analysis of possibilities of using the comparable thick separator in sandwich structures is fulfilled. Correlation between value of giant magneto-impedance ratio on single amorphous ribbon and sandwich structure creation is revealed.

PL

Przebadano olbrzymi magneto- opór w strukturze wielowarstwowej na amorficznych stopach metali Co80-xNixB20 (x = 4, 6, 8, 10, 12 at.%) dla prądu zmiennego z częstotliwością zmieniającą się od 1 do 3000 kHz przy zastosowaniu pola magnetycznego. Dokonana została analiza możliwości wykorzystania porównywalnego separatora grubości w strukturze wielowarstwowej. Przedstawiono korelację między wartością współczynnika olbrzymiego magneto-oporu na pojedynczej wstędze amorficznej a tworzeniem się struktury wielowarstwowej.

12

Dynamic Analysis of Sandwich Structure in Presence of Shock

Abdennadher M., Wali M., Fakhfakh T., Haddar M.

Machine Dynamics Problems

|

2009

|

Vol. 33, No. 2

5-18

EN

Sandwich structures have been broadly used in civil and aerospace engineering. The configuration of sandwich panels with two stiff face sheets and viscoelastic core provides high energy absorption capability. In this work we study the dynamic behaviour of sandwich plate in presence of shock. The shock is modelled by a contact between sandwich plate and a fixed rigid solid. A numeric model is developed based on Newmark implicit model. At the shock location, two conditions are imposed on the contact nodes: the displacement in these nodes must be lower or equal to the distance which separate sandwich plate from rigid solid and the velocity is null. The dynamic results prove the attenuation of vibrations for sandwich structure.

13

Badania pękania udarowego w konstrukcjach przekładkowych poliestrowo-szklanych z rdzeniem z pianki PVC

Wojtyra R., Imielińska K.

Kompozyty

|

2007

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R. 7, nr 3

140-144

PL

Porównano podatność do pękania udarowego trzech konstrukcji przekładkowych z okładkami z laminatu poliestrowo-szklanego i rdzeniem z pianki PVC za pomocą dynamicznych charakterystyk obciążeń/odkształceń oraz badań mikrostrukturalnych. Zastosowano trzy rodzaje spoiwa (Scott Bader) do połączenia okładek z rdzeniem: spoiwo dwufazowe z twardym napełniaczem, spoiwo lekkie z napełniaczem w postaci mikrosfer oraz żywicę poliestrową (przyklejanie pianki do nieutwardzonych powłok). Obciążenie inicjacji pęknięć było niezależne od spoiwa i wyniosło ok. 2,5 kN dla wszystkich próbek. W badaniach quasi-statycznych wartość ta okazała się niższa: 1,2-1,7 kN. Największą podatność do pękania poprzez rdzeń wykazały próbki ze spoiwem dwufazowym zawierającym twarde cząstki. Badania sekwencji pękania próbek przy użyciu kamery do szybkiej fotografii pozwoliły ustalić, że powodem tego była słaba adhezja na granicy spoiwo-pianka (pękanie miało charakter adhezyjny) w przeciwieństwie do próbek z lekkim spoiwem zawierającym mikrosfery, gdzie pęknięcie miało charakter kohezyjny. Najskuteczniejszym w warunkach udaru spoiwem okładek i rdzenia okazała się sama żywica poliestrowa w procesie formowania "na mokro".

EN

Impact resistance of glass/polyester-PVC foam core sandwich structures was studied using instrumented impact tests. The efficiency of three face core bonding agents was estimated: the two Scott Bader adhesives (the high density, and the low density) and polyester resin (wet lay-up). The load (deflection-) time plots were analyzed in terms of the threshold load for impact damage and maximum impact load. With the aid of high-speed photography the damage initiation load was found approximately 2.5 kN, independent of the adhesive type compared to 1.2-1.7 kN obtained in the quasi-static indentation tests. It was found that for low velocity impact loading high density adhesive was the least effective face/core bonding agent since the core crack originated from the adhesive/core interfacial fracture while for the low density bonding agent cohesive fracture occurred. Resin-bonded specimens were most resistant to the development of the face/core fracture.

14

Perspektywy zastosowania konstrukcji sandwiczowej w kontrolowanych strefach zgniotu lekkiego pojazdu szynowego

Grabowiecki K., Krasucki J.

Zeszyty Naukowe. Transport / Politechnika Śląska

|

2005

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z. 60

51-60

PL

Konstrukcje lekkich pojazdów szynowych, oprócz zapewnienia odpowiedniej wytrzymałości na obciążenie statyczną siłą wzdłużną, wymagają zwiększenia odporności na zderzenie w zakresie ochrony operatora oraz pasażerów. Zapewnienie kontrolowanej strefy zgniotu można uzyskać zarówno poprzez właściwą strukturę konstrukcji pudła wagonu, jak i przez dobór właściwości materiałowych elementów pochłaniających energię. W tym celu możliwe jest wykorzystanie koncepcji mikro skrzynki typu I-core z wypełnieniem pianką.

EN

The concept of light rail vehicles demands for additional study dedicated to its crashworthiness. There are distinguished two groups of design parameters to satisfy the crash energy management: structure configuration and material properties. Two engineering solutions are considered to satisfy that demand: the application of I-core panels and the foam-filling concept.

15

Analiza porównawcza sztywności i częstości drgań swobodnych struktur z tektury falistej

Marynowski K., Kołakowski Z., Mania R.

Przegląd Papierniczy

|

2003

|

R. 59, nr 8

491-494

PL

W pracy przedstawiono model tektury falistej jako trójwarstwowej, kompozytowej struktury charakteryzującej się ortotropią konstrukcyjną rdzenia. Zaprezentowano kolejne etapy weryfikacji przedstawionego modelu przy zastosowaniu metody elementów skończonych. W celu ułatwienia zrozumienia, proces modelowania został opisany z pominięciem zależności matematycznych. W pracy przedstawiono wyniki obliczeń numerycznych częstości drgań swobodnych giętnych, sztywności na zginanie (D11, D22) oraz sztywności na rozciąganie/ściskanie (a11) struktur płaskich mikrofali E oraz fali średniej C.

EN

Three-layered composite Structure as the model of Corrugated board is presented in this paper. The composite has been modeled as the thin-walled laminate construction with orthotropic core. The successive stages of the presented model verification by using the finite element method are shown. To facilitate the intelligibility the modeling process has been described without mathematical dependences. Numerical investigations results of the transverse natural frequencies, the flexural rigidities (D11, D22), and the tension/compression rigidities (A11) of the E-profile and the C profile flat structures of the corrugated board are presented in the paper.

16

An investigation into integral sandwich structures

Młyniec M.

Research Bulletin / Warsaw University of Technology, Institute of Aeronautics and Applied Mechanics

|

1999

|

nr 9

197-206

EN

The main aim of this project was the evaluation of Integral Sandwich Structures (ISS) for aeronautical industry applications. Flexural, shear and impact properties of Integral Sandwich materials established and compared with the properties of commonly used honeycomb-core sandwich structures. Four kinds of tests were out: - The flexural and shear modulus of the material investigated using a new draft standard proposed by the National Physics Laboratory (London). An evaluation of the test method was an additional aim of the project. - The flexural strength of the material was tested using a three-point bending test according to the ISO 178 standard. - The inter-laminar shear (ILS) strength was tested according to the ISO 14125 standard. - Dropweight impact tests were carried out to the ISO 6603 standard. Further on, the costs of production of Integral Sandwich Structures were evaluated and strength by density by cost ratios were calculated for both materials. A closer look was also taken at the properties of the new sandwich structure concerning design and repair and finally an evaluation of the material made and its possible applications in the aeronautical industry were discussed. The tested material has proved to be cheaper and easier to lay up than traditional sandwich structures, but the specific properties acquired in the flexural, shear. and impact tests were equal or inferior to honeycomb structures.