Papers by Keyword: Dynamic Mechanical Analysis

Abstract: In general, composite materials are widely used in many industries. A composite material is a material composed of two or more components. Such a composite material differs in its properties from the individual components of the entire composite. This contribution is aimed at evaluating the parameters of selected composite materials - wood fiber boards, carbon prepreg boards and epoxy boards. The measured quantities that were investigated on the given materials were the modulus of elasticity, the loss modulus and the tan delta angle. To evaluate the properties of the given composite materials, a dynamic-mechanical analysis using the DMA Q800 device from TA Instruments was used. Three samples were measured from each material. From the measured values, it is demonstrable for the modulus of elasticity that the greatest mechanical disturbance began to occur gradually due to the influence of temperature and frequency with three materials in this order: fiber board - carbon prepreg board - epoxy board. From the obtained values ​​of the loss modulus, it was proven that the sample - wood fiber board - had the lowest glass transition temperature. Finally, regarding the measured values ​​of the glass transition temperature for the loss angle (tan delta), it can be said that the wood fiber board also has the lowest damping ability.

Abstract: Mechanical and thermal properties of composites reinforced with Banana fibre (BF) and Sisal fibre (SF) were investigated in this study. Benzoylation therapy was effective for Banana fibre /Sisal. The hybridised bio-composites (PP/BF/SF) with a total 10 weight percentage were produced using three different fibres ratios between Banana fibre - and Sisal-treated. The thermal stability experiments are performed using thermogravimetric analysis (TGA) and diffraction scanning calorimetry (DSC). According to flammability test results, the treated hybrid composite (BF / PP /SF) burned at the slowest rate (only 28 mm/min) and the stiffness damping factor (Tan δ). The loss modulus (E "the ideal (PP/BF/SF) hybrid composite, T-BF5SF5, has a damping factor of 0.058 and a modulus of 86.2 (MPa). Thermomechanical analysis (TMA) was also used to effectively record the dimensional coefficient (m) versus temperature studies, with T-BF5SF5 achieving the highest dimensional coefficient (m) of 30.11 at 110°C. Keywords: Sisal; biocomposites; Banana fibre ; dynamic mechanical analysis; thermal; benzoylation.

Abstract: For the purpose of this investigation, carbon and Kevlar fiber-reinforced plastics were subjected to dynamic testing. Carbon-Kevlar fibers are included into the LY 556 resin and AR 951 hardener. Fiber makes for 40% of the study's total weight. The carbon and Kevlar composites were created by hand lay-up. The orientation considered in this research is 0/0 and 0/90 for both carbon and Kevlar composites. Advanced characterizations such as TMA and DMA has been integrated in this research. By using DMA (Dynamic Mechanical Analyzer) and the thermomechanical Analyzer (TMA), the dynamic properties were acquired. ASTM E756 was used to conduct the tests. Composite heating at room temperature to 120⁰ C was the temperature variable under investigation. The studies were conducted on TMA and DMA with a force of 0.002N, respectively. DMA uses a three-point bending loading design for its samples. Temperature affects the dimensions, storage modulus, loss modulus, and tan delta.

Abstract: Co-Pоly (Urethane-Imide) s (CPUI) based on pоly (diethyleneglycol) adipate diol, tolylenediisocyanate, multinucleate dianhydrides and diamines were synthesized. The films and moldings from CPUI were processed and their mechanical characteristics were evaluated. Distinctions of specifications of the films formed from polymer solutions and the moldings formed from melt polymers are indicated when using the same starting CPUI. It appears that films and moldings possess typical properties of elastomers. The reprocessing of studied copolymers by using the injection molding method allows to assign CPUI to the thermoplastic elastomers or so-called thermoelastoplasts.

Abstract: AbstractEpoxy syntactic foams (SF) filled with hollow glass microspheres (HGM) were prepared by simple resin casting method and characterization in this study. The effect of varying the amount of HGM on the specific mechanical and water absorption properties of SF composites were investigated. Five different composition of SF (SFT60-0.5 to SFT60-2.5) were compared with the neat epoxy matrix. The wall thickness of the microballoons differ because of its different percentile size distribution (10^th, 50^th and 90^th), which reflects in its density variation. The results show that the specific tensile and flexural strength increases with an increasing filler (HGM) content. The density of SF filled with HGM reduces with increasing volume fraction of filler content. Scanning electron microscopy was done on the failed samples to examine the fractured surfaces. The water absorption capacity of the SF was also investigated as it relates to the HGM volume fraction variation. All the syntactic foam composition shows a better diffusion coefficient capacity than the neat epoxy resin. This makes it applicable in structural purposes and several marine application products such as Autonomous Ultimately Vehicle (AUV).

Abstract: In this article Therban AT 5065 VP, Therban AT 5005 VP - HBNR elastomers of different unsaturation degrees and their combined compositions research results (using optical and atomic force microscopy, DSC, DMA) are described. With these results structure and functional properties operational data of nitrile elastomers was obtained with no need of durable tests under different temperatures. It was found out that filler dispersion rises from 61.8 to 90.5 % and decomposition temperature grows from 261.9 to 275.3 °C while Therban AT 5005 VP share is increased from 20 to 50 weight parts. It is shown that elastomers with rubber ratio of 50:50 within temperature range from minus 30 to plus 150 °C have the lowest elasticity coefficient (from 311 to 1.6 MPa) and mechanical loss tangent (0.20) at the end of the test.

Abstract: The exceptional mechanical and thermal properties, conceivable with carbon nanotubes (CNTs) make a distinction of them as excellent choices for natural rubber nanocomposite reinforcement. Nigeria, in recent years, has been awash with foreign prostheses, many of which fail to meet the criteria of the International Society of Prosthetics and Orthotics (ISPO) for developing countries. However, there are major marked gaps that make them susceptibility to premature failure and dimensional instability, caused by a high rate of water absorption in a humid environment; owing to the dynamic nature of human gait. This paper critically examines the effect of water absorption, thermogravimetric and dynamic mechanical properties, on carbon nanotube-reinforced natural rubber nanocomposite (NC) for prosthetic foot application. CNTs were synthesised via catalytic chemical vapour deposition (CCVD) technique and the NCs were produced by using an electrically heated hydraulic press. Thermogravimetric analysis (TGA), water absorption rate and dynamic mechanical analysis (DMA) of the nanocomposites were carried out with a view to comparing the various compositions used in this paper. Of the five NCs developed (NR/MWCNT-0, NR/MWCNT-3, NR/MWCNT-6, NR/MWCNT-9, NR/MWCNT-12 and NR/MWCNT-15), NR/MWCNT-3 (3 g of MWCNT in 100 g of natural rubber) showed the highest thermal stability of 260 °C, optimal water absorption rate of 0.1% and highest quality energy storage and dissipation capacity, as indicated by 2.239 DMA loss factor curve amplitude, hence giving it a comfortable edge over its existing counterparts. The results of the various analyses carried out indicated, therefore, that reinforcing natural rubber with multi-walled carbon nanotube offers a reliable alternative material for the prosthetic industry.

Abstract: The series of compositions containing thermodynamically incompatible flexible blocks of aliphatic polyesters and rigid blocks of aromatic bis (urethane) imides in the volume of polymers was obtained on the basis of multiblock (segmented) poly (urethane-imides) and related aromatic polyimides. The series includes segmented poly (urethane-imides) with different relative content of flexible and rigid blocks, non-segregating mixtures of poly (urethane-imides) and thermoplastic partially crystalline polyimide, statistical copolymers of poly (urethane-imide) with imide, and non-segregating mixtures of statistical copolymers with thermoplastic polyimide. The derived polymer systems were studied using thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. The deformation and strength properties of film samples are determined. It is shown that the properties of the studied polymers change as their content of imides blocks increases, and the transition from thermoplastic poly (urethane-imide) elastomers to thermoplastic polyimides is observed.

Abstract: The effects of the carbon fiber (CF), carbon black (CB) and nanosilica (SiO₂) on the mechanical properties of the phenolic resin (PF) were studied and the optimum composition was selected for the preparation of quaternary composites (CF/CB/SiO₂ phenolic composites). The incorporation of poly (acrylonitrile-co-butadiene) rubber (NBR) to strengthen the quaternary composites were also studied. The morphological, mechanical and thermo-mechanical properties of unmodified and NBR modified-quaternary phenolic composites were investigated. The phenolic compounds were mixed by ball milling and the phenolic composites were fabricated by hot compression molding. Scanning electron microscopy images of NBR modified-quaternary phenolic composites show the high fracture surface roughness. The results show that the addition of 5 wt% NBR in the quaternary composites offer the highest tensile strength and Young’s modulus which are significantly improved by 176% and 235%, respectively, and they also offer the high flexural strength, impact strength and flexural modulus which are improved by 79%, 29% and 12%, respectively, compared to neat PF. The glass transition temperature (T_g) of unmodified and NBR modified-quaternary phenolic composites are higher than that of neat PF (107.3 °C). The increase of NBR content does not deteriorate T_g of the quaternary phenolic composites. This study provides a new pathway for making advanced phenolic composites.

Abstract: This paper presents the results of an experimental program to study the mechanical properties of currently available composite materials for the construction of wind turbine blade. The materials identified for this purpose include unidirectional glass fibre/epoxy (GFRP), carbon fibre/epoxy (CFRP) and hybrid combinations of these two materials to be used in a laminated design and at elevated temperatures. The tests conducted in the present programme includes short beam shear test and dynamic mechanical analysis tests after the specimens are exposed to temperatures ranging from 25 to 140°C. The results indicate that the inter-laminar shear failure strength and stiffness of GFRP, CFRP and hybrid specimens degrade with increasing temperature. However, the degradation is observed to be higher in single material specimens in comparison to hybrid specimens. In particular, stiffness of CFRP specimens decreased linearly as the temperature approached 40°C and increased up to the glass transition temperature of epoxy. Experimental results indicated that damping properties of Glass-Carbon-Glass/epoxy specimens improved at elevated temperatures which is important for noise and vibration control. In the present study, empirical models are proposed based on the test data to predict the variation of inter-laminar shear failure stress and stiffness as a function of temperature. The experimental results and proposed model can be used as input parameters to design and construct composite wind turbine blades to be used in tropical wind farms.