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  • Open Access


    Oxidative Degradation of Thermoplastic Starch Induced by UV Radiation

    Mayte M. Quispe1,*, Olivia V. López1, Marcelo A. Villar1,2

    Journal of Renewable Materials, Vol.7, No.4, pp. 383-391, 2019, DOI:10.32604/jrm.2019.04276

    Abstract Among biopolymers, thermoplastic starch (TPS) is a good candidate to obtain biomaterials because of its natural origin, biodegradable character, and processability. Exposure to ultraviolet (UV) radiation causes significant degradation of starch-based materials, inducing photooxidative reactions which result in breaking of polymer chains, production of free radical, and reduction of molar mass. These changes produce a deterioration of TPS mechanical properties, leading to useless materials after an unpredictable time. In this work, changes induced on TPS by UV radiation, analyzing structural properties and mechanical behavior, are studied. TPS was obtained through thermo-mechanical processing of native corn starch in the presence of… More >

  • Open Access


    Computational Simulation of Mechanical Behavior of Semi-Crystalline Polymers with Randomly Distributed Rubber Particles

    M. Uchida1, N. Tada1, Y. Tomita2

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.6, No.2, pp. 91-98, 2008, DOI:10.3970/icces.2008.006.091

    Abstract Micro- to mesoscopic deformation behavior of semi-crystalline polymer with randomly distributed rubber particles is evaluated by numerical simulation. In this model, dimension of mesostructure is identified by volume fraction of interface region around the rubber particles. The effects of strain rate and size of mesostructure on macroscopic stress-strain relation and strain distribution in mesoscopic area are discussed. In the earlier stage of deformation, the slope of stress-strain relation changes by rubber particle size while stress in the following deformation is mainly affected by the tensile strain rate. The anisotropic deformation in lamellar oriented interface region causes change in the strain… More >

  • Open Access


    On the Influence of Mechanical Behavior of the Middle Ear Ligaments: a Finite Element Analysis

    Fernanda Gentil1, Renato Natal Jorge2, António Joaquim Mendes Ferreira3, Marco Parente4, Pedro Martins5, Eurico de Almeida6

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.9, No.1, pp. 45-56, 2009, DOI:10.3970/icces.2009.009.045

    Abstract The interest in finite element method (FEM) concerning biomechanics has been increasing, in particular, to analyze the mechanical behavior of the human ear. In this work, a finite element model of the middle ear was made. A dynamic study based on a structural response to harmonic vibrations, for different sound pressure levels, applied on the eardrum, is presented using the ABAQUS program. The model includes different ligaments and muscle tendons with elastic and hyperelastic behavior of these supportive structure. The non-linear behavior of the ligaments and muscle tendons was considered, being the connection between ossicles done by contact formulation. Harmonic… More >

  • Open Access


    Effect of Cellulose Nanocrystals on Fire, Thermal and Mechanical Behavior of N,N’-Diallylphenylphosphoricdiamide Modified Poly(lactic acid)

    Weijun Yang1†, Xiaomin Zhao2†, Elena Fortunati1, Franco Dominici1, Jose M. Kenny1, Debora Puglia1*, De-Yi Wang2*

    Journal of Renewable Materials, Vol.5, No.5, pp. 423-434, 2017, DOI:10.7569/JRM.2017.634146

    Abstract Presented herein is a deep investigation of the fire, mechanical and thermal performances of poly(lactic acid) (PLA)-based nanocomposites, which were obtained by combining cellulose nanocrystals (CNC) with various contents of N,N’-diallyl-phenylphosphoricdiamide (P-AA) via a two-steps masterbatch melt extrusion process (glycidyl methacrylate grafting on PLA and CNC premixing with PLA). Results have shown that the value of the limiting oxygen index (LOI) increased to 28.8% and a V-0 rating in UL94 test was obtained when 2 wt% of P-AA was added in the presence of cellulose nanocrystals (3 wt%). The incorporation of CNC induced a decrease of both PHRR and THR… More >

  • Open Access


    Biodegradable PLA/PBAT/Clay Nanocomposites: Morphological, Rheological and Thermomechanical Behavior

    Juan P. Correa1,2*, Alejandro Bacigalupe2,3, Jorge Maggi4, Patricia Eisenberg2,3

    Journal of Renewable Materials, Vol.4, No.4, pp. 258-265, 2016, DOI:10.7569/JRM.2016.634117

    Abstract Poly(lactic acid)/poly(butylene adipate-co-terephthalate) (PLA/PBAT)-based nanocomposites were prepared by melt blending of PLA and PBAT with 5 wt% of unmodified (Cloisite Na) and modified (Cloisite 30B) montmorillonites. X-ray diffraction (XRD) revealed an intercalated structure in both nanocomposites. The extent of the intercalation was higher for nanocomposites based on modified clays (OMMT) with chemical affinity with the polymer matrix. Rheological measurements have shown an increase in viscosity and a better degree of clay dispersion for nanocomposites containing OMMT. Nanocomposites with OMMT showed lower PBAT separated phase particle size and improvements in thermal stability, mechanical properties and water vapor barrier when compared with… More >

  • Open Access


    Mechanical Behaviors and Deformation Properties of Retaining Wall Formed by Grouting Mould-Bag Pile

    Shengcai Li1,*, Jun Tang1,2, Lin Guo3

    Structural Durability & Health Monitoring, Vol.13, No.1, pp. 61-84, 2019, DOI:10.32604/sdhm.2019.06058

    Abstract The simplified mechanical model and finite element model are established on the basis of the measured results and analysis of the grouting pile deformation monitoring, surface horizontal displacement and vertical displacement monitoring, deep horizontal displacement (inclinometer) monitoring, soil pressure monitoring and seepage pressure monitoring in the lower reaches of Wuan River regulation project in Shishi, Fujian Province. The mechanical behavior and deformation performance of mould-bag pile retaining wall formed after controlled cement grouting in the silty stratum of the test section are analyzed and compared. The results show that the use of controlled cement grouting mould-bag pile technology is to… More >

  • Open Access


    Surface Electric Gibbs Free Energy and Its Effect on the Electromechanical Behavior of Nano-Dielectrics

    Ying Xu1, Shengping Shen1,2

    CMC-Computers, Materials & Continua, Vol.28, No.1, pp. 81-96, 2012, DOI:10.3970/cmc.2012.028.081

    Abstract This paper considers the surface effect through the surface and bulk electric Gibbs free energy. The analytical expressions are derived for the effective elastic, dielectric and piezoelectric modulus for nano-structural elements in electromechanical coupling problems. Numerical examples for PZT are given to illustrate the size effects on the electromechanical properties of nano-particles, nano-wires and nano-films quantitatively. The solution shows that the electromechanical properties of piezoelectric nano-material are size-dependent but the size effects on the elastic property and dielectric property are different. More >

  • Open Access


    AFM and Nanoindentation Studies of Bone Nodules on Chitosan-Polygalacturonic Acid-Hydroxyapatite Nanocomposites

    R. Khanna1,2, D. R. Katti1, K. S. Katti1

    CMES-Computer Modeling in Engineering & Sciences, Vol.87, No.6, pp. 530-556, 2012, DOI:10.3970/cmes.2012.087.530

    Abstract Here we report a new in situ nanoindentation technique developed to evaluate the composite mechanical behavior of cell-biomaterial construct under physiological conditions over the time scale of bone nodule generation. Using this technique, mechanical behavior of osteoblast cell-substrate interfaces on tissue engineered materials (chitosan-polygalacturonic acid-nanohydroxyapatite (CPH) films) is investigated. Mechanical behavior of cells in the elastic regime over the time scale of cell adhesion (1 day), proliferation (4 days), development (8 days) and maturation (22 days) of bone nodules is evaluated. Our results indicate that the elastic properties of flat cells are higher (indicating stiffer response, after 4 days, as… More >

  • Open Access


    Methodology for Numerical Simulation of Trabecular Bone Structures Mechanical Behavior

    M.A. Argenta1, A.P. Gebert2, E.S. Filho3, B.A. Felizari4, M.B. Hecke5

    CMES-Computer Modeling in Engineering & Sciences, Vol.79, No.3&4, pp. 159-182, 2011, DOI:10.3970/cmes.2011.079.159

    Abstract Various methods in the literature proposesequations to calculate the stiffness as a function of density of bone tissue such as apparent density and ash density among others[Helgason, Perilli, Schileo, Taddei, Brynjolfsson and Viceconti, 2008]. Other ones present a value of an equivalent elasticity modulus, obtained by statistical adjustments of curves generated through mechanical compression tests over various specimens[Chevalier, Pahr, Allmer, Charlebois and Zysset, 2007; Cuppone, Seedhom, Berry and Ostell, 2004]. Bone tissue is a material withdifferent behaviors according to the scale of observation. It has a complex composite hierarchical structure, which is responsible for assign optimal mechanical properties. Its characteristics,… More >

  • Open Access


    Assessment of Mixed Uniform Boundary Conditions for Predicting the Mechanical Behavior of Elastic and Inelastic Discontinuously Reinforced Composites

    D. H. Pahr1, H.J. Böhm1

    CMES-Computer Modeling in Engineering & Sciences, Vol.34, No.2, pp. 117-136, 2008, DOI:10.3970/cmes.2008.034.117

    Abstract The combination of heterogeneous volume elements and numerical analysis schemes such as the Finite Element method provides a powerful and well proven tool for studying the mechanical behavior of composite materials. Periodicity boundary conditions (PBC), homogeneous displacement boundary conditions (KUBC) and homogeneous traction boundary conditions (SUBC) have been widely used in such studies. Recently Pahr and Zysset (2008) proposed a special set of mixed uniform boundary conditions (MUBC) for evaluating the macroscopic elasticity tensor of human trabecular bone. These boundary conditions are not restricted to periodic phase geometries, but were found to give the same predictions as PBC for the… More >

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