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1

Tensile, impact, and mode-I behaviour of glass fiber-reinforced polymer composite modified by graphene nanoplatelets

Vigneshwaran G. V., Shanmugavel Balasivanandha Prabu, Paskaramoorthy R., Harish Sivasankaran

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 3

439--453

EN

This paper reports the tensile, impact, and mode-I behaviour of glass fiber-reinforced polymer (GFRP) composites modified by incorporating graphene nanoplatelets (GnPs) on the fiber surface and in the epoxy matrix. The composites were fabricated through a hand lay-up technique followed by hot compression moulding. The homogeneous dispersion of GnPs in the matrix was achieved by mechanical mixing followed by ultra-sonication. The glass fibers were coated with varying quantities of GnPs (GnPs in epoxy) by the dip-coating technique. The composites containing 1 wt% GnPs on both the fiber surface and the matrix (0.5 wt% deposited on the fiber and 0.5 wt% dispersed in epoxy) enhanced the impact resistance by 45% and tensile strength by 114% over the pristine composite. The mode I fracture toughness of the composite containing 1 wt% GnPs on both the fiber surface and the matrix was increased by 55% with the crack parallel to the fiber direction and 64% in a crack perpendicular to the fiber direction over the pristine composite. The presence of GnPs at the fiber/matrix interface toughened the fiber surface by preventing the matrix from cracking.

2

Low-energy impact behaviour and damage characterization of carbon fibre reinforced polymer and aluminium hybrid laminates

Bieniaś J., Jakubczak P., Surowska B., Dragan K.

Archives of Civil and Mechanical Engineering

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2015

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Vol. 15, no. 4

925--932

EN

The purpose of this paper is to investigate the impact behaviour and damage characterization of carbon fibre reinforced aluminium hybrid laminates (Al/CFRP) in comparison to classic carbon fibre reinforced polymer (CFRP) at low-velocity and low-energy impact. Impact damage characteristic with damage initiation and progression, internal failure modes and understanding of the role of the metal layers in the impact behaviour under low-energy were examined and discussed. The damage mechanism of the tested laminates is very complex. There is an internal degradation of the material, with the plastic deformation in case of fibre metal laminates. Characteristic matrix cracks (bending and shearing cracks) running at the fibre–matrix interface in composite layers are the first damage mode. The critical damage mode is delaminations observed between composite layers with different orientation as well as delaminations at the metal–composite interface in fibre metal laminates. For the tested materials, particularly carbon fibre reinforced composites, the absorbed impact energy is mainly connected with elastic response and damage of the laminate. In case of fibre metal laminates the absorbed energy is also connected with plastic deformation of the laminate, occurring especially in the metal layers. High impact resistance of fibre metal laminates indicates that metal (aluminium) layers may prevent delamination propagation and impactor penetration.

3

Investigation of Textiles Elastic Properties with a Pendulum Impact Device

Valatkienė L., Strazdienė E., Issa M.

Fibres & Textiles in Eastern Europe

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2008

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Vol. 16, no. 2 (67)

52--57

EN

This investigation concerns the estimation of materials impact behaviour based on the registration of vibration during the pendulum process. In order to find optimal testing conditions, three types of materials: woven fabric, knitted material and polyethylene membrane were chosen and two bobs of different weight and radius (r1=13.5 mm, r2=30 mm) were applied. The initial angles α0 of the pendulum were: 1; 2; 3; 4 and 5 degrees. To describe the impact behavior of the materials, the impact values and rebound angles of each stroke were used and the elasticity properties of the materials were determined: rebound elasticity εr and dynamic elasticity εd, on the basis of the initial potential energy V0 of the pendulum and its energy after one full swing V1. A close relationship exists between rebound elasticity εr, dynamic elasticity εd and initial angles α0 of the pendulum for all the test materials under different testing conditions. Percentage values of absorbed energy H1 of the test materials at the first moment of pendulum impact were calculated. It was established that linear regression analysis can be applied to establish dependencies between absorbed energy H1 of the material at the moment of first impact, as well as the pendulum’s potential energy V1 after a full swing period and the first rebound angle α1.

PL

Badania dotyczyły określenia udarowej charakterystyki materiałów włókienniczych na podstawie rejestracji drgań wywołanych uderzeniem wahadła. Przygotowano trzy typy materiałów: tkaniny, dzianiny i membrany polietylenowe oraz dwa obciążniki o różnej masie i wymiarach r1 = 13,5 mm, r2 = 30 mm. Początkowy kąt wahadła α0 wynosił 1, 2, 3, 4 i 5 stopni. Parametry uderzenia i kąt odbicia każdego z uderzeń notowano a właściwości elastyczne materiału (elastyczność odprężeniowa er i dynamiczna εd) określano na podstawie początkowej energii wahadła Vo i jego energii po jednym pełnym wahnięciu V1. Stwierdzono, zależność pomiędzy elastycznością odprężeniową er i dynamiczną εd a kątem początkowym a0 dla wszystkich testowanych materiałów i różnych warunkach przeprowadzania testów. Obliczano procentową wartość absorbowanej energii h1 badanego materiału w pierwszym momencie uderzenia wahadła. Stwierdzono, że można zastosować regresję liniową dla określenia zależności pomiędzy zaabsorbowaną przez materiał badany energię H1 w momencie pierwszego uderzenia wahadła oraz energią potencjalną V1 po pełnym okresie wahnięcia a pierwszym kątem odbicia α1.

4

Low velocity impact damage in glass / polyester composite sandwich panels

Lendze T., Wojtyra R., Guillaumat L., Biateau C., Imielińska K.

Advances in Materials Science

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2006

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Vol. 6, nr 1

26-34

EN

Impact resistance of glass/polyester facesheets/PVC foam core sandwich structures was primarily assessed in terms of skin-/core bonding efficiency using two types of adhesives and bonding with uncured resin. Also, the air-coupled ultrasonic C-scan technique was estimated as a means of characterizing impact damage size in sandwich structures. The following observations were made. The impact damage size estimated by visual inspection was much more extensive in all samples, which is due to the C-scan images showing only the overlapping delaminations area directly under the impact site, whereas the visual inspection of the laminate surface and macroscopic observations of the sample section show the extent of the largest, single delamination. The least extensive damage size was found in the two-phase high-density adhesive samples showing also the highest tendency for core cracking. In contrast, the “pinkglue” adhesive, which is low-density due to the presence of the microspheres provides greater local flexibility which prevented core craking.

5

Advanced epoxy composites of improved impact tolerance

Imielińska K., Wojtyra R.

Kompozyty

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2004

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R. 4, nr 9

61-67

EN

The materials aspects of improved low velocity impact tolerance have been reviewed. These include: tougher matrix systems, controlling fibre/matrix interfacial bond strength, using woven and mixed woven fibre fabrics, protective layers, stitching, Z-pinning, hybrid reinforcement, 3D structures, non-crimp fabrics NCF. For current structures, Z pinning shows the most promise, although the cost associated with this concept is currently high. For future structures, 3D woven materials show significant promise for impact tolerant design. As an illustration to the problem selected experimental results from the authors' work on low velocity impact (rebound) behaviour were presented for hybrid glass/carbon/epoxy and glass/epoxy toughened with phenolic microspheres as well as aramid-glass with three different matrix types. The results showed that toughening epoxy matrix with phenolic microspheres had positive effect on absorbed impact energy (Figs 3, 4). The second phase acts to absorb significant amount of energy during fracture through mechanisms of crack front bowing and crack splitting. Changing to a tougher resin system has a number of advantages, most notably an increase in delamination resistance. However, other mechanical properties of tougher materials tend to be reduced, particularly compression dominated properties, which may suffer due to increased matrix compliance. Protective layer of aramid-glass fabric had minor effect on impact characteristics but was found promising in terms of perforation resistance. Interlayer woven carbon/glass-fibre/epoxy composites are used in practice in the construction of composite marine crafts at critical points of the glass/epoxy structure where improved stiffness is needed. The results obtained in this study for glass/carbon composites and in the previous work show (Figs 3, 4) that interlayer woven carbon/glass-fibre/epoxy composites exhibit high impact energy absorption combined with high strength. Impact damage resistance and impact damage tolerance of glass/carbon/epoxy composites depends on the stacking sequence of the laminate.

PL

Przedstawiono przegląd sposobów poprawy tolerancji udarów w nowoczesnych laminatach polimerowych. Są to: wytrzymalsze i bardziej ciągliwe materiały osnowy, dobieranie odpowiedniego powiązania osnowy i włókien, stosowanie włókien w postaci tkanin, zszywanie preform z wielu warstw tkanin, łączenie włókien ciągłych w preformy za pomocą kompozytowych szpilek, stosowanie tkanin NCF z włókien ciągłych łączonych na grubości dodatkowym oplotem, wzmocnienie hybrydowe, warstwy ochronne z innych włókien. Jako ilustrację problemu przedstawiono niepublikowane, wybrane wyniki badań autorów naświetlające zachowanie kompozytów hybrydowych szklano-weglowych i szklanych o osnowie wzmocnionej mikrosferami z żywicy fenolowej oraz kompozytu szklanego z ochronną warstwą tkaniny aramidowo-szklanej. Wykazano, że wzmocnienie osnowy epoksydowej mikrobalonami fenolowymi ma pozytywny wpływ na absorpcję energii sprężystej (rys. rys. 3 i 4) dzięki mechanizmowi rozszczepiania końcówki pęknięcia i wyginania frontu pęknięcia. Wzmocnienie osnowy polimerowej utrudnia powstawanie delaminacji, jednak inne właściwości mechaniczne kompozytów o wzmocnionej osnowie ulegają nieznacznemu pogorszeniu. Ochronna warstwa aramidowo-szklana nie wpłynęła znacząco na poprawę absorpcji energii laminatu szklanego. Hybrydowe kompozyty wzmocnione warstwami włókien szklanych i węglowych są stosowane w praktyce w krytycznych miejscach konstrukcji kadłuba, gdzie wymagana jest podwyższona sztywność. Przedstawiono wyniki badań absorpcji energii laminatów o układzie warstw powierzchniowych: szkło/szkło/węgiel oraz węgiel/szkło i porównano z wcześniejszymi wynikami badań wpływu kolejności warstw węgiel/szkło na tolerancję udaru w próbie poudarowej wytrzymałości na ściskanie.