Effect of chemical treatment on newspaper fibers reinforced polymer poly(vinyl chloride) composites

Natural fibers used as reinforcement in composite materials present specific mechanical properties, which are comparable to glass fibers. In addition, they have the advantage of being renewable and recyclable. However, their main drawback is their inherent susceptibility to moisture expansion, which has the effect of inducing a decrease in mechanical properties, and of debonding in the composite. In this study, lignocellulosic fibers from newspapers were modified with acetic anhydride, NaOH, and KMnO₄ in order to enhance the interfacial adhesion between poly(viny lchloride) (PVC) matrix and the newspaper fibers. Composites samples were prepared with different treated fibers at the same loading (20 wt%). X‐ray and scanning electron microscopy (SEM) were used to characterize the fiber's surfaces. The mechanical, morphological, and thermal properties of PVC/newspaper composites were also studied. Moreover, the maximum improvement in the mechanical properties (tensile strength) was obtained for the permanganate treated PVC/newspaper composites. J. VINYL ADDIT. TECHNOL., 22:173–181, 2016. © 2014 Society of Plastics Engineers     

Dual boundary element method modelling of aircraft structural joints with multiple site damage

The computation of crack growth from a bolt or rivet hole in a structural joint practically requires that the geometry be approximated to some degree. In this paper a simplified quasi-2D stress analysis method, using the boundary element method is presented, where the load transfer rate and the contact stresses at the hole edge for the full 3D geometry are fairly well approximated. Coupled with a dual boundary element formulation for the crack propagation problem, this model is used to evaluate stress intensity factors for through cracks emanating from holes in several double shear lap joint configurations. As the calculated stress intensity factors compare well with experimental data, this procedure is considered to approximate satisfactorily the load transfer rate and the contact stresses at the hole edge of the full 3D geometry, when secondary bending is not a factor.     

Properties of poly(lactic acid)/montmorillonite/carbon nanotubes nanocomposites: determination of percolation threshold

Incorporation of rigid nanoparticles is the most effective means of improving polymer properties. Montmorillonite (MMT) and multi-walled carbon nanotubes (MWCNTs) are legendary in this field for their individual exceptional properties. A synergistic phenomenon is induced between these two particles when they are simultaneously incorporated into polymers. At a definite nanofillers concentration, called the percolation threshold, there is a sudden change in nanocomposite properties due to the formation of a 3D-structured network of the nanoparticles within the matrix. In this work, the properties of poly(lactic acid) (PLA) nanocomposites filled with different fractions of MMT/MWCNTs hybrid (0.5–2.0 wt%) were analyzed. In particular, the percolation threshold of the MMT/MWCNTs hybrid was uniquely identified by differential scanning calorimetry, thermogravimetric analysis and dynamic mechanical thermal analysis. The structural studies by X-ray diffraction and Fourier-transform infrared spectroscopy were also associated with the percolation threshold of MMT/MWCNTs in PLA. At 1.0 wt% MMT/MWCNTs concentration, the complete exfoliation of the particles was maintained, and the thermal characteristics such as glass transition, crystallization and melting temperatures reached their plateau at this hybrid concentration. Moreover, the thermal degradation and viscoelastic parameters showed their peak values at this critical point, which is correlated with the formation of the percolation threshold within the matrix. The morphological studies confirmed the homogeneous dispersion of MMT/MWCNTs in PLA up to a concentration of 1.0 wt%. At 2.0 wt% MMT/MWCNTs, few aggregations occurred in the PLA-based composite, confirming that the percolation threshold was formed at a lower concentration of MMT/MWCNTs nanoparticles.

     

Prediction of reliability analysis of composite tubular structure under hygro-thermo-mechanical loading

The present paper focuses on reliability prediction of composite structure under hygro-thermo-mechanical loading, conditioned by Tsai-Wu failure criterion, where the Monte–Carlo method is used to estimate the failure probability(Pf). This model was developed in two steps: first, the development of a deterministic model, based on an analytical and numerical approach, and then, a probabilistic computation. Using the hoop stress for each ply, a sensitivity analysis was performed for random design variables, such as materials properties, geometry, manufacturing, and loading, on composite cylindrical structure reliability. The probabilistic results show the very high increase of failure probability when all parameters are considered.     

Maximum likelihood difference scaling of image quality in compression-degraded images

Lossy image compression techniques allow arbitrarily high compression rates but at the price of poor image quality. We applied maximum likelihood difference scaling to evaluate image quality of nine images, each compressed via vector quantization to ten different levels, within two different color spaces, RGB and CIE 1976 L*a*b*. In L*a*b* space, images could be compressed on average by 32% more than in RGB space, with little additional loss in quality. Further compression led to marked perceptual changes. Our approach permits a rapid, direct measurement of the consequences of image compression for human observers.     

Study of the effect of gamma irradiation on the structure and properties of metallocene linear low density polyethylene containing hindered amines

The changes in the carbonyl index, the melt flow rate, the crystalline content and the ultimate tensile properties of metallocene linear low density polyethylene (mLLDPE) films subjected to gamma irradiation from 10 to 800 kGy, were investigated with and without hindered amine stabilizer (HAS). For comparative purposes, unstabilized and HAS stabilized low density polyethylene (LDPE) were also studied. The results indicated that under gamma irradiation, the HAS stabilizer did not have any influence on the oxidative stability of mLLDPE films as compared with unstabilized ones due probably to complexation reactions between the nitroxyl radicals of the stabilizer and the metallocene catalysts leading to inert species. Moreover, higher increases in melt flow index and crystalline content with a fast drop in ultimate tensile properties were observed for higher doses indicating the occurrence of chain scission. It was also found that the metallocene LLDPE structure had no significant effect on the radiation induced oxidative degradation kinetics when compared to LDPE. Whereas, the addition of HAS to LDPE significantly lowered the formation rates of carbonyls and subsequently improved the durability of the material by doubling the half-value-dose.     

Sulfuric Containing Sugar Bath and Permanent Weak Magnetic Field Effect during Anodizing AlCu<Subscript>6</Subscript>Si Alloy Sheet Surfaces

Rolling and perpendicular to rolling surfaces of AlCu₆Si aluminum sheet have been anodized at 27 ± 1°C in 20 wt % sulfuric acid containing an additive of white sugar powder with and without permanent weak magnetic field. After one hour of anodizing, some hillocks-shaped micropores are developed and craters are formed in the oxide layers. The micropores obtained in rolling faces are often smaller than those obtained on other faces. Sulfuric anodizing at 21 V causes the formation of combined micropore-nanopore structures in rolling surface. It demonstrated that sugar additive increases the density of micropores in spherical shape in rolling surface and the increasing of sugar concentration changes the pores to hillocks form. In addition, the application of weak magnetic field induces homogeneous repartition of micropores.     

Urban landscape structure anatomy: Structure patterns and typology identification in the space-time of Setif City,Algeria

The definition of urban form and its elements raises a wide debate in urban morphology. This study presents a proposal to understand the structuring of the urban landscape of Setif City over 170 years (1848-2018) by abstracting its main elements into permanent structure (PS_UL). It corresponds to the street network, more static to the change of the town plan, and flexible structure (FS_UL), more resilient to change and explains the superimpositions of morphological components (plot, building, and land use). This work aims to identify typological patterns of structures suggested in space-time through the inspection of the growth of the street network and the filling of morphological layers framed by the concept of urbanity. The methodology is based on syntactic (diachronic) morphogenetic analysis, with statistical analyses as unsupervised classification. Results indicate that PS_UL presents an accumulation of microincrements produced with a similar degree of coherence in different urban fabrics, which explain the local patterns of street network structuring. The typology of FS_UL patterns indicates an unbalanced growth by the arrangement between morphological elements, resulting in a variation in the degree of urbanity.     

Integrating the LSSVM and RBFNN models with three optimization algorithms to predict the soil liquefaction potential

Engineering with Computers - Liquefaction has caused many catastrophes during earthquakes in the past. When an earthquake is occurring, saturated granular soils may be subjected to the liquefaction...     

Hybrid descriptor and optimized CNN with transfer learning for face recognition

Multimedia Tools and Applications - This work focuses on the development of optimized algorithms applied in the field of Face Recognition (FR). The strategy adopted represents the contribution of...