Theoretical study of the effect of thermal stress on transversal damage of hybrid biocomposite materials Flax-Hemp / Polyethylene

2021 ◽  
Vol 14 ◽  
Author(s):  
Allel Mokaddem ◽  
Bendouma Doumi ◽  
Mohammed Belkheir ◽  
Ahmed Boutaous ◽  
Elhouari Temimi

Background: The objective of sustainable development in the field of materials necessitates and demands the substitution of the basic constituents of a composite material (carbon, glass, etc.) by natural reinforcements, which have a very important role in the protection of the environment and to subsequently have new materials with good properties compared to so-called traditional materials. Objective: In this context, we have investigated, using genetic modeling based on probabilistic models, the effect of thermal stress on transversal damage of a bio-composite hybrid Flax-Hemp/PE material. Method: Our model genetic is based on probabilistic models of Weibull and the different values of the thermal stress was calculated by the Lebrun equation. We used the nonlinear parameter β in the Hoock law of the nonlinear acoustic technique to trace the curves of the damage under the mechanical and thermal stress to validate our theoretical calculations. Results: The results obtained with a genetic simulation are in good agreement with the results found by Clément GOURIER and Raphaël KUENY, who have shown that flax and hemp fibers (bark/Liberian fibers) are good reinforcements of the Polyethylene matrix, we found also found that our hybrid biocomposite material Flax-Hemp/PE is resistant in particular, a part of this material is of plant origin and gives us environmental benefit. Conclusion: It should be noted that the results obtained by the genetic simulation are in good agreement with the results obtained by the nonlinear acoustic technique mentioned by the green curve in all the figures. In perspective, it would be interesting to see, later, the effect of humidity on the damage of the matrix fiber interface of a hybrid biocomposite.

2019 ◽  
Vol 23 (1) ◽  
pp. 253-258
Author(s):  
Salima Sadat ◽  
Allel Mokaddem ◽  
Bendouma Doumi ◽  
Mohamed Berber ◽  
Ahmed Boutaous

Abstract In this paper, we have studied the effect of thermal stress on the damage of fiber-matrix interface of a hybrid biocomposite composed of two natural fibers, Hemp, Sisal, and Starch matrix. Our genetic modeling used the nonlinear acoustic technique based on Cox’s analytical model, Weibull’s probabilistic model, and Lebrun’s model describing the thermal stress by the two coefficients of expansion. The stress applied to our representative elementary volume is a uni-axial tensile stress. The numerical simulation shows that the Hemp- Sisal/Starch hybrid biocomposite is most resistant to thermal stresses as compared with Hemp/Starch biocomposite. It also shows that hybrid biocomposite materials have a high resistance to applied stresses (mechanical and thermal) compared to traditional materials and biocomposite materials. The results obtained in our study coincide perfectly with the results of Antoine et al., which showed through experimental tests that natural fibers perfectly improve the mechanical properties of biocomposite materials.


BioResources ◽  
2020 ◽  
Vol 15 (3) ◽  
pp. 7079-7099
Author(s):  
Jianying Chen ◽  
Guojing He ◽  
Xiaodong (Alice) Wang ◽  
Jiejun Wang ◽  
Jin Yi ◽  
...  

Timber-concrete composite beams are a new type of structural element that is environmentally friendly. The structural efficiency of this kind of beam highly depends on the stiffness of the interlayer connection. The structural efficiency of the composite was evaluated by experimental and theoretical investigations performed on the relative horizontal slip and vertical uplift along the interlayer between composite’s timber and concrete slab. Differential equations were established based on a theoretical analysis of combination effects of interlayer slip and vertical uplift, by using deformation theory of elastics. Subsequently, the differential equations were solved and the magnitude of uplift force at the interlayer was obtained. It was concluded that the theoretical calculations were in good agreement with the results of experimentation.


1979 ◽  
Vol 57 (22) ◽  
pp. 2967-2970 ◽  
Author(s):  
Gabriel Llabrès ◽  
Marcel Baiwir ◽  
Léon Christiaens ◽  
Jean-Louis Piette

The 1Hmr study of the title compounds has revealed a screw conformation, with defined interconversion processes, in good agreement with crystal structure determinations and theoretical calculations. The mesomeric effect of the heteroatom is smaller than in the anisole series, due to steric inhibitions.The 13Cmr enhances, to some extent, these conclusions. In the case of Te compounds, a heavy atom effect adds to the classical mesomeric and inductive effects to account for the experimental observations.


The first section of this paper is an account of some experiments on the absorption of light in sodium vapour from the series limit at 2412 Å to about 1600 Å (an energy difference of 2·6 eV). The absorption cross-section at the limit is 11·6 ± 1·2 x 10 -20 cm 2 . The cross-section decreases giving a minimum of 1·3 ± 0·6 x 10 -20 cm 2 at 1900 Å and then increases to 1600 Å. A theoretical calculation by Seaton based on the dipole-length formula gives good agreement with the experiments at the series limit and also correctly predicts the wave-length for the minimum, but it predicts a significantly lower absorption at the minimum. The experiments described in the first section of the paper conclude a series on the absorption of light in the alkali metals. The second section consists of a general discussion of the results of these experiments and of their relation to theoretical calculations. There is good agreement between theory and experiment except in regard to the magnitude of the absorption at the minimum.


2018 ◽  
Vol 2018 ◽  
pp. 1-7
Author(s):  
Ran Zhao ◽  
Bo-wen Wang ◽  
Quan-guo Lu ◽  
Jian-wu Yan ◽  
Xiao-cui Yuan

Magnetostrictive biomimetic whiskers have been used as tactile and flow sensors. Compared to other types of whiskers, such whiskers have the advantage of being able to perform static and dynamic measurements. For dynamic measurement, the whisker’s resolution changes with varying vibration frequency; however, the mechanism for this influence has not been studied yet. Thus, the aim of this study is to investigate the resolution–frequency correlation. First, the structure and operation principle of the whisker were analyzed. Then, the Euler–Bernoulli beam theory was employed to establish the sensing model of the magnetostrictive whisker. Finally, the mapping relationship between sensor resolution and frequency was obtained. The eigenfrequency analysis was implemented by FEM to obtain the frequency response of the whisker. A vibration experimental system was built for dynamic testing. The experimental results were in good agreement with the theoretical calculations. Furthermore, it was noted that the resolution was positively correlated with frequency, and the maximum resolution was attained at the natural frequency (two peak values appeared at the first-order and second-order eigenfrequencies). Our research reveals the manner in which a whisker sensor’s resolution is affected by the vibration frequency. The theoretical model can be used to predict the resolution of magnetostrictive whisker sensors.


1983 ◽  
Vol 36 (6) ◽  
pp. 897 ◽  
Author(s):  
DD Richardson ◽  
J Mahanty

We present a deformation dipole model based on theoretical calculations of induced moments in ion pairs. The model is generally applicable and in this paper is applied to the calculation of the lattice dynamics of NaCI. Only a few parameters are required to give good agreement with experiment. Limitations of the approach are discussed.


Author(s):  
Ying Xie ◽  
Ze Wang ◽  
Xueting Shan ◽  
Yangyang Li

Purpose Thermal stress of the rotor in a squirrel cage induction motor is generated due to the temperature rise, and the structure of the rotor will be destroyed if the stress acted on the rotor exceeds its limits, so the thermal stress is also one of the main causes led to broken bar fault. The purpose of this paper is to report the thermal stress coupled analysis for the induction motor with healthy and faulty rotor, and to find the variation tendency of the temperature and thermal stress due to broken bars, and the part most likely to break in the rotor as a result of the thermal stress load are identified. Design/methodology/approach The steady temperature and thermal stress of the rotor in the case of the healthy and faulty conditions are calculated by finite element method, and the 3D model of the motor used in the experiments is established and the experimental results are presented for both healthy and faulty machines. Findings The influence of the broken bars fault on the motor thermal profile and thermal stress can be found, and it explains why the breaking point always appears in the joint of the bars and end rings. Originality/value The paper presents the 3D thermal stress coupled model and performance characteristics of induction motor with broken bars. The reasonable constraint is established according to the contact of components each other, and more reasonable fracture location is selected. The results obtained by the simulation model are in a good agreement with practical situation, because the effect of skewed rotor were taken into consideration in the process of simulation.


2006 ◽  
Vol 20 (01) ◽  
pp. 49-61 ◽  
Author(s):  
F. BENKABOU

We have used the molecular-dynamic method for the calculation of the structural, dynamic and elastic properties of group BeS , BeSe and BeTe compounds for temperature ranging from 300 to 1200 K. Tersoff potential has been used to model the interaction between the groups II–VI compound atoms. The structural properties of cubic BeS , BeSe and BeTe have been calculated, and good agreement between the calculated and experimental values have been found. We have also predicted the elastic constants and diffusion coefficients of BeS , BeSe and BeTe . The values found compare very well with the theoretical results. For the temperature range under study, all elastic constants and dynamic properties show a softening with increasing temperature very similar to the theoretical calculations.


2018 ◽  
Vol 23 (2) ◽  
pp. 241-266 ◽  
Author(s):  
Ximena Verónica Jaramillo-Fierro ◽  
César Zambrano ◽  
Francisco Fernández ◽  
Regino Saenz-Puche ◽  
César Costa ◽  
...  

A new Cu(I) complex constructed by reaction of trithiocyanuric acid (ttc) and copper (II) perchlorate hexahydrate has been successfully synthesized by a slow sedimentation method in a DMF solvent at room temperature. The molecular structure of the compound was elucidated by MALDI-TOFMS, UV Vis and FTIR spectroscopy, DSC-TGA analysis and magnetic susceptibility measurement. The proposed structure was corroborated by a computational study carried out with the Gaussian09 and AIMAII programs using the RB3LYP hybrid DFT functional with both 6-31G and Alhrich-TZV basis sets. The calculated vibrational frequencies values were compared with experimental FTIR values. Photophysical properties of the synthesized complex were evaluated by UV-Visible spectroscopy and compared with computed vertical excitation obtained from TDDFT. The theoretical vibrational frequencies and the UV Vis spectra are in good agreement with the experimental values. Additionally, the Frontier Molecular Orbitals (HOMO-LUMO) and the Molecular Electrostatic Potential of the complex was calculated using same theoretical approximation. The results showed the interaction between three coordinatedl igand atoms and the Cu(I) ion.


1989 ◽  
Vol 44 (5) ◽  
pp. 480-484 ◽  
Author(s):  
Martin Saunders ◽  
Gary W. Cline ◽  
Max Wolfsberg

The rapid, degenerate 1,2-hydride shift in 2,3-dimethyl-2-butyl cation in stable solution in SbF5/SO2C1F was perturbed by deuterium and 13C leading to splittings observed by 13C NMR spectroscopy over a range of temperatures. Accurate values for equilibrium isotope effects were obtained from these data. Theoretical calculations of the equilibrium isotope effects were performed using the Gaussian-86 program to obtain an optimized geometry and the Cartesian force constant matrix, followed by the program QUIVER which applies the Bigeleisen-Mayer method. When all of the conformers, which are in rapid equilibrium, were considered specifically, quite good agreement between theory and experiment was obtained.


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