scholarly journals About the Dynamic Behaviour of Composite Bars Reinforced with Cotton or Hemp Fibers

2020 ◽  
Vol 31 ◽  
pp. 49-54
Author(s):  
A. I. Radoi ◽  
C. M. Miritoiu
Keyword(s):  
Epoxy Resin ◽  
Unit Length ◽  
Young Modulus ◽  
Free Vibrations ◽  
Acquisition System ◽  
Cotton Fibers ◽  
Mass Unit ◽  
Hemp Fibers ◽  
Beam Dynamic ◽  
The Matrix

In this paper, the authors designed several green composites with natural reinforcements (hemp and cotton fibers) and the matrix is a synthetic resin (epoxy resin). On having produced the samples, the authors determined the dynamic mechanical characteristics. The dynamic parameters were determined from the bar free vibrations. The next experimental rig was used: the bars were clamped at one end and left free at the other end. At the free end, a Bruel&Kjaer accelerometer with 0.04 pC/ms-2 sensitivity was placed, in order to record the beam dynamic response. A force was applied at the free end to bend the beams, and after bending, the force was cancelled and the beams were left to vibrate freely. The accelerometer was connected to a Nexus signal conditioner, and the signal conditioner was connected to a SPIDER 8 data acquisition system made by Hottinger Baldwin Messtec. The acquisition system was connected to a notebook and the experimental parameters were obtained through the CATMAN EASY software. From the free vibrations recording, the next mechanical parameters were determined: the eigenfrequency of the first eigenmode, the damping factors per mass unit and per unit length, the loss factor and the dynamic Young modulus and stiffness. From the results obtained, it can be concluded that the materials with epoxy resin reinforced with hemp have better vibration damping properties as compared to the composites made from epoxy reinforced with cotton fibers.

scholarly journals Dynamic behaviour of composites reinforced with needles from fir trees

2021 ◽  
Vol 343 ◽  
pp. 01001
Author(s):  
Alexandru Ioan Rădoi ◽  
Cosmin Mihai Miriţoiu ◽  
Mihaela Bogdan ◽  
Marius Marinel Stănescu ◽  
Dumitru Bolcu ◽  
...  
Keyword(s):  
Data Acquisition ◽  
Dynamic Stiffness ◽  
Unit Length ◽  
Young Modulus ◽  
Data Acquisition System ◽  
Free Edge ◽  
Free Vibrations ◽  
Acquisition System ◽  
Damping Factor ◽  
The Matrix

In this paper we build some composite materials reinforced with needles from fir trees. In order to build the samples, we have firstly created some strips in this way: we put the pines, continuously, on a sheet of paper where we apply a thin layer of resin (we have used epoxy and polyester ones). We have made 10 strips and we have glued them together by using the same synthetic resins (epoxy and polyester). In the end we have obtained some composites reinforced with strips from fir trees needles and paper sheet, and the matrix is made from epoxy and polyester resins. From the obtained plate, we have cut some samples in order to study their free vibrations. We have placed an accelerometer at about 10 mm from the free edge and we have clamped the samples on several free lengths. The accelerometer is connected to a signal conditioner NEXUS which is also connected to a data acquisition system SPIDER 8. The data acquisition system is connected to a notebook through USB port. From the samples free vibrations, we have determined: the eigenfrequency, the damping factor per unit mass, damping factor per unit length, dynamic stiffness, dynamic Young modulus and loss factor.

About the Mechanical Properties for Composites Reinforced with Felt

2021 ◽  
Vol 42 ◽  
pp. 30-35
Author(s):  
Alexandru Ioan Rădoi ◽  
Cosmin Mihai Miriţoiu ◽  
Alexandru Bolcu ◽  
Valeriu Ionică ◽  
Alina Elena Romanescu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Epoxy Resin ◽  
Testing Machine ◽  
Young Modulus ◽  
Optical Microscope ◽  
Elongation At Break ◽  
The Matrix ◽  
Static Mechanical ◽  
Static Mechanical Properties ◽  
Made In

In this paper we present some researches about the static mechanical properties for some composites made in this way: the reinforcement is made from two types of felt and the matrix is from epoxy resin Resoltech 1050 with its hardener Resoltech 1055. There are built some plates from felt/epoxy resin and from these plates there are cut some samples. The samples are tensile loaded on an universal testing machine Instron 1000 HDX which is assisted by a BlueHill software. There are determined the next mechanical properties: Young modulus, yield strength, elongation at break and breaking strength. By using an optical microscope, there are presented some images with the breaking sections.

Researches about the Dynamic Behavior of Green Composites Reinforced with Rush and Bulrush

2021 ◽  
Vol 42 ◽  
pp. 24-29
Author(s):  
Alexandru Ioan Rădoi ◽  
Cosmin Mihai Miriţoiu ◽  
Mihaela Bogdan ◽  
Marius Marinel Stănescu ◽  
Dumitru Bolcu ◽  
...  
Keyword(s):  
Data Acquisition System ◽  
Dynamic Mechanical Properties ◽  
Free Vibrations ◽  
Acquisition System ◽  
Unit Mass ◽  
Damping Factor ◽  
Dynamic Parameters ◽  
Green Composites ◽  
Experimental Parameters ◽  
The Matrix

The paper presents some researches about the dynamic mechanical properties for some green composites made as follows: the reinforcement is made from rush and bulrush and the matrix is from epoxy resin Resoltech 1050 with its hardener Resoltech 1055. The dynamic parameters were determined from the bars free vibrations. In the first part of the paper, there are presented the mathematical calculus formulas used for the dynamic parameters determination based on the experimental recordings for the free vibrations. The next experimental montage was used: the bars were clamped at one end and were left free at the other end. At the free end, a Bruel&Kjaer accelerometer with 0.04 pC/ms-2 sensitivity was placed in order to record the beams dynamic response. A force was applied at the free end to bend the beams and after bending, the force was cancelled and the beams were left to freely vibrate. The accelerometer was connected to a signal conditioner Nexus and the signal conditioner was connected to a data acquisition system SPIDER 8 made by Hottinger Baldwin Messtec. The acquisition system was connected to a notebook ant the experimental parameters were obtained through CATMAN EASY software. From the free vibrations recording, the following mechanical parameters were determined: the eigenfrequency of the first eigenmode and the damping factors per unit mass. With these values, we have determined some direct calculus formulas for the damping factor per unit mass.

scholarly journals The Influence of Mixing Methods of Epoxy Composition Ingredients on Selected Mechanical Properties of Modified Epoxy Construction Materials

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 411
Author(s):  
Izabela Miturska ◽  
Anna Rudawska ◽  
Miroslav Müller ◽  
Monika Hromasová
Keyword(s):  
Tensile Strength ◽  
Epoxy Resin ◽  
Construction Materials ◽  
Preliminary Heating ◽  
Epoxy Composition ◽  
Mixing Speed ◽  
Adhesive Composition ◽  
Adhesive Compositions ◽  
The Matrix ◽  
Level Of Significance

The proper process of preparing an adhesive composition has a significant impact on the degree of dispersion of the composition ingredients in the matrix, as well as on the degree of aeration of the resulting composition, which in turn directly affects the strength and functional properties of the obtained adhesive compositions. The paper presents the results of tensile strength tests and SEM microphotographs of the adhesive composition of Epidian 57 epoxy resin with Z-1 curing agent, which was modified using three fillers NanoBent ZR2 montmorillonite, CaCO3 calcium carbonate and CWZ-22 active carbon. For comparison purposes, samples made of unmodified composition were also tested. The compositions were prepared with the use of six mixing methods, with variable parameters such as type of mixer arm, deaeration and epoxy resin temperature. Then, three mixing speeds were applied: 460, 1170 and 2500 rpm. The analyses of the obtained results showed that the most effective tensile results were obtained in the case of mixing with the use of a dispersing disc mixer with preliminary heating of the epoxy resin to 50 °C and deaeration of the composition during mixing. The highest tensile strength of adhesive compositions was obtained at the highest mixing speed; however, the best repeatability of the results was observed at 1170 rpm mixing speed. Based on a comparison test of average values, it was observed that, in case of modified compositions, the values of average tensile strength obtained at mixing speeds at 1170 and 2500 rpm do not differ significantly with the assumed level of significance α = 0.05.

scholarly journals Hemp Fiber Reinforced Red Mud/Fly Ash Geopolymer Composite Materials: Effect of Fiber Content on Mechanical Strength

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 511 ◽  
Author(s):  
Eyerusalem A. Taye ◽  
Judith A. Roether ◽  
Dirk W. Schubert ◽  
Daniel T. Redda ◽  
Aldo R. Boccaccini
Keyword(s):  
Fly Ash ◽  
Mechanical Strength ◽  
Red Mud ◽  
Fiber Reinforced ◽  
Brazilian Tensile Strength ◽  
Hemp Fiber ◽  
Hemp Fibers ◽  
The Matrix ◽  
Geopolymer Composites ◽  
Scanning Electron

Novel hemp fiber reinforced geopolymer composites were fabricated. The matrix was a new geopolymer based on a mixture of red mud and fly ash. Chopped, randomly oriented hemp fibers were used as reinforcement. The mechanical properties of the geopolymer composite, such as diametral tensile (DTS) (or Brazilian tensile) strength and compressive strength (CS), were measured. The geopolymer composites reinforced with 9 vol.% and 3 vol.% hemp fiber yielded average DTS values of 5.5 MPa and average CS values of 40 MPa. Scanning electron microscopy (SEM) studies were carried out to evaluate the microstructure and fracture surfaces of the composites. The results indicated that the addition of hemp fiber is a promising approach to improve the mechanical strength as well as to modify the failure mechanism of the geopolymer, which changed from brittle to “pseudo-ductile”.

scholarly journals Assessing the Flexural Properties of Epoxy Composites with Extremely Low Addition of Cellulose Nanofiber Content

2020 ◽  
Vol 10 (3) ◽  
pp. 1159 ◽  
Author(s):  
Yingmei Xie ◽  
Hiroki Kurita ◽  
Ryugo Ishigami ◽  
Fumio Narita
Keyword(s):  
Mechanical Properties ◽  
Epoxy Resin ◽  
Flexural Modulus ◽  
Strengthening Mechanism ◽  
Short Fiber ◽  
Cellulose Nanofiber ◽  
Resin Matrix ◽  
Element Analysis ◽  
Epoxy Resin Matrix ◽  
The Matrix

Epoxy resins are a widely used common polymer due to their excellent mechanical properties. On the other hand, cellulose nanofiber (CNF) is one of the new generation of fibers, and recent test results show that CNF reinforced polymers have high mechanical properties. It has also been reported that an extremely low CNF addition increases the mechanical properties of the matrix resin. In this study, we prepared extremely-low CNF (~1 wt.%) reinforced epoxy resin matrix (epoxy-CNF) composites, and tried to understand the strengthening mechanism of the epoxy-CNF composite through the three-point flexural test, finite element analysis (FEA), and discussion based on organic chemistry. The flexural modulus and strength were significantly increased by the extremely low CNF addition (less than 0.2 wt.%), although the theories for short-fiber-reinforced composites cannot explain the strengthening mechanism of the epoxy-CNF composite. Hence, we propose the possibility that CNF behaves as an auxiliary agent to enhance the structure of the epoxy molecule, and not as a reinforcing fiber in the epoxy resin matrix.

Investigation of Fiber-Reinforced Modified Epoxy Resin Composites

2012 ◽  
Vol 510-511 ◽  
pp. 577-584 ◽  
Author(s):  
A. Quddos ◽  
Mohammad Bilal Khan ◽  
R.N. Khan ◽  
M.K.K. Ghauri
Keyword(s):  
Epoxy Resin ◽  
High Strength ◽  
Polymeric Matrix ◽  
Fiber Reinforced Composites ◽  
Resin Matrix ◽  
Reinforced Composites ◽  
Fiber Reinforced ◽  
Epoxy Resin Matrix ◽  
The Matrix ◽  
Modified Epoxy

The impregnation of the fiber with a resin system, the polymeric matrix with the interface needs to be properly cured so that the dimensional stability of the matrix and the composite is ensured. A modified epoxy resin matrix was obtained with a reactive toughening agent and anhydride as a curing agent. The mechanical properties of the modified epoxy matrix and its fiber reinforced composites were investigated systematically. The polymeric matrix possessed many good properties, including high strength, high elongation at break, low viscosity, long pot life at room temperature, and good water resistance. The special attentions are given to the matrix due to its low out gassing, low water absorption and radiation resistance. In addition, the fiber-reinforced composites showed a high strength conversion ratio of the fiber and good fatigue resistance. The dynamic and static of the composite material were studied by thermo gravimetric analysis (TGA), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM) with EDX. The influences of processing technique such as curing and proper mixing on the mechanical and interfacial properties were determined. The results demonstrated that the modified epoxy resin matrix is very suitable for applications in products fabricated with fiber-reinforced composites.

The Damping Study for Dammar Composites Reinforced with Natural Fibers

2015 ◽  
Vol 801 ◽  
pp. 188-193
Author(s):  
Dumitru Bolcu ◽  
Marius Marinel Stănescu ◽  
Cosmin Mihai Miriţoiu ◽  
Cristian Oliviu Burada
Keyword(s):  
External Force ◽  
Natural Fibers ◽  
Free Vibrations ◽  
Vibration Damping ◽  
Initial Deformation ◽  
Rectangular Section ◽  
Hemp Fibers ◽  
Free Length ◽  
Natural Resin

In this paper we have studied the vibration damping for composite bars made by dammar based natural resin, the reinforcement being made by flax, cotton, silk and hemp fibers. There were made rectangular section samples (5x10 mm) with 220 mm length. The bars were clamped, the free length being 100 mm, 120 mm, 140 mm, 160 mm and 180 mm. For each bar, the free vibrations made by an initial deformation, obtained by inserting an external force in the free end, were recorded. In each case, the measured vibration was under-damped.

An Improved Method for Calculating Free Vibrations in Systems of Several Degrees of Freedom

1938 ◽  
Vol 5 (2) ◽  
pp. A61-A66
Author(s):  
Winston M. Dudley
Keyword(s):  
Degrees Of Freedom ◽  
Numerical Solutions ◽  
Matrix Theory ◽  
Free Vibrations ◽  
Initial Disturbance ◽  
Improved Method ◽  
Matrix Methods ◽  
Computing Machine ◽  
The Matrix ◽  
Time Required

Abstract In 1934 two English investigators (1) published a method for calculating the various modes and frequencies of vibration of a system having several degrees of freedom. Their method, which is based on matrices, greatly shortens the time spent in obtaining numerical solutions in many important problems, notably those with immovable foundations. In this paper is presented a new theorem which (a) makes possible a further reduction of nearly one half in the time required, so that solutions up to 20 deg or more of freedom are now practical and (b) makes it then possible to determine the motion of the system after any initial disturbance in a few minutes, instead of several hours as required by older methods. It is useful in the latter respect whether the modes have been determined by matrix methods, or not. Although the paper gives simpler proofs than any previously published, knowledge of the matrix theory is not required in using the method. Problems are analyzed by a tabular process, in which an ordinary computing machine helps greatly. Comments based on computing experience are given. A simple numerical example has been given elsewhere (1).

Innovative technologies in corrosion-resistant coatings development aimed at ship navigation equipment protection

2021 ◽  
Vol 103 (3) ◽  
pp. 5-12
Author(s):  
Oleh Bezbakh
Keyword(s):  
Residual Stresses ◽  
Epoxy Resin ◽  
Epoxy Matrix ◽  
Phthalic Acid ◽  
Epoxy Oligomer ◽  
Acid Anhydride ◽  
Molecular Formula ◽  
Innovative Technologies ◽  
Composite Formation ◽  
The Matrix

The efficient use of some innovative technologies in adhesives with advanced operational characteristics development aimed at anti-corrosion properties increase of transport means has been substantiated in the paper under discussion. The above-mentioned technologies involving the use of some interaction-active ingredients forming the cross-linkable coatings composition, including some polymers, have provided their cohesion properties essential improvement. Epoxy diane oligomer ED-16 has been chosen as the main component for the matrix in the composite formation. The aliphatic resin DЕG-1 (GOST 10136-77) as a plasticizer has been added to the epoxy oligomer. The compound has been formed of the following concentration: epoxy resin ED-16: plasticizer DЕG -1 – 100: 40. The hardener of cold hardening polyethelenepolyamine PEPA (ТУ 6-05-241-202-78) has been used at the epoxy resin-based developed materials polymerization. Phthalic acid anhydride has been used as a modifier to improve the properties of epoxy composite materials. The modifier was added to the matrix in the following ratio: from 0,10 to 2,00 pts.wt. per 100 pts.wt. of epoxy oligomer ЕD-20. The molecular formula of the modifier is as follows: C8H4O3. Molar mass is 148,1 g/mol. Density is ρ = 1,52 г/см³. To form a composite material or a protective coating with some improved adhesive properties and inconsiderable residual stresses the phthalic acid anhydride as a modifier was found to be added to the epoxy matrix with the content q = 1,25 pts.wt. per 100 pts.wt. of the epoxy matrix (oligomer ЕD-20 + plasticizer DЕG -1). In this case, the adhesive strength of the coating is being increased from sа = 28,3 MPа to sа = 46,4 MPа, and residual stresses – from sз = 1,9 MPа to sз = 2,1 MPа. First of all, the improved properties of the modified materials were caused by the interaction of active carbonyl (С=О) groups of the modifier with nitrogen-containing (NH-) groups of the hardener. It has provided the increase of the composite cross-linking degree resulted in their both adhesive and cohesion properties improvement. Moreover, it was found that the modifier use in the compound with the content q = 1,0…1,5 00 pts.wt. per 100 00 pts.wt. of the matrix has provided the increase of the river water influenced coatings resistance from ρ = 12,1 Оm·cm2 до ρ = 21,2…22,4 Оm·cm2. Though, some further increase of the additive content in the coating has caused the deterioration of anti-corrosion characteristics of the materials. Thus, the conducted study has contributed to the determination of the most efficient content ratio of phthalic acid anhydride as a modifier to for the coatings of functional use.

Sign in / Sign up

Export Citation Format

Share Document