Structure-property relationships in extruded plastics foams

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Physical properties and morphology of extruded semicrystalline polymers can be significantly affected by modification and change in die design and melt viscosity of the molten polymer. Further modifications to physical properties (i.e. density and open cell fraction) of foamed material occur, following the modification of melt viscosity by melt blending of polypropylene and high density polyethylene). The main object of this research project was to carry out a systematic examination of rheological properties of polymer/gas mixture, affect of die design, polymer molecular weight (melt viscosity), and processing conditions on density, open cell fraction, cell morphology (i.e. cell size and cell size distribution) and micromorphology of polyolefin foams. Also attention was given to method of stabilisation of extruded foam, where, it was found support of the extrudated foam (by adding a specially designed die adapter to the end of the die) prior to entering the cooling tank could result not only to a specimen with uniform cross section, but also due to drop in melt temperature, the cell walls are to some extent rigidized, hence, the collapse of bubbles are limited. From commercial point of view control of cell collapse, density and open cell fraction, will make these foamed materials valuable for their filtration characteristics. Microstructural analysis of polypropylene (unfoamed state) by X-ray diffraction and Differential Scanning Calorimetry revealed 13-spherulites are only formed in skin layer, and beneath the thickness of 500 pm from the surface, the crystal structure of this polymer is only consist of B-spherulites. On the other hand, the chemical blowing agent (Hydrocerol CF-20), was found to have nucleating affect on microstructure of polypropylene, where, it has resulted in reduction of size of spherulites together with a drop in recrystallisation temperature and formation of P and a spherulites through the thickness of extrudated foam. The foregoing chemical blowing agent was found to have no significant affect on the crystal structure of the high density polyethylene

A New Method for Multisensor Data Fusion Based on Wavelet Transform in a Chemical Plant

Abstract This paper presents a new multi-sensor data fusion method based on the combination of wavelet transform (WT) and extended Kalman filter (EKF). Input data are first filtered by a wavelet transform via Daubechies wavelet "db4" functions and the filtered data are then fused based on variance weights in terms of minimum mean square error. The fused data are finally treated by extended Kalman filter for the final state estimation. The recent data are recursively utilized to apply wavelet transform and extract the variance of the updated data, which makes it suitable to be applied to both static and dynamic systems corrupted by noisy environments. The method has suitable performance in state estimation in comparison with the other alternative algorithms. A three-tank benchmark system has been adopted to comparatively demonstrate the performance merits of the method compared to a known algorithm in terms of efficiently satisfying signal-tonoise (SNR) and minimum square error (MSE) criteria

Electrochemical and Mechanical Properties of Ni/g-C3N4 ‎Nanocomposite Coatings with Enhanced Corrosion Protective ‎Properties: A Case Study for Modeling the Corrosion Resistance ‎by ANN and ANFIS Models

This work investigates the effect of electrolysis bath parameters on the corrosion, micro-hardness, and wear behavior of Ni coatings. The characterization of synthesized Graphitic carbon nitride (g-C3N4) was done by Fourier transform infrared, Raman spectroscopy, and transmission electron microscope. The surface morphology of coated samples with various amounts of current density was studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The corrosion prevention effect of Ni/g-C3N4 nanocomposite coatings was investigated by EIS and polarization techniques. The experimental outcome demonstrates that an electrolysis bath of 0.3 g/L g-C3N4 and 0.1 A.cm-2 presents a Ni coating with the highest corrosion protection, wear resistance, and microhardness. The corrosion current densities of Ni/g-C3N4 coatings obtained by electrochemical tests were used for training two machine learning techniques (Artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS)) based on current density, g-C3N4 concentration, and plating time as an input. Various statistical criteria showed that the ANFIS model (R2= 0.99) could forecast corrosion current density more accurately than ANN with R2= 0.91. Finally, due to the robust performance of ANFIS in modeling the corrosion behavior of Ni/g-C3N4 nanocomposite coating, the effect of each parameter was studied

Surface Pretreatments of AA5083 Aluminum Alloy with Enhanced Corrosion Protection for Cerium-Based Conversion Coatings Application: Combined Experimental and Computational Analysis

The effects of surface pretreatments on the cerium-based conversion coating applied on an AA5083 aluminum alloy were investigated using a combination of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), polarization testing, and electrochemical impedance spectroscopy. Two steps of pretreatments containing acidic or alkaline solutions were applied to the surface to study the effects of surface pretreatments. Among the pretreated samples, the sample prepared by the pretreatment of the alkaline solution then acid washing presented higher corrosion protection (~3 orders of magnitude higher than the sample without pretreatment). This pretreatment provided a more active surface for the deposition of the cerium layer and provided a more suitable substrate for film formation, and made a more uniform film. The surface morphology of samples confirmed that the best surface coverage was presented by alkaline solution then acid washing pretreatment. The presence of cerium in the (EDS) analysis demonstrated that pretreatment with the alkaline solution then acid washing resulted in a higher deposition of the cerium layer on the aluminum surface. After selecting the best surface pretreatment, various deposition times of cerium baths were investigated. The best deposition time was achieved at 10 min, and after this critical time, a cracked film formed on the surface that could not be protective. The corrosion resistance of cerium-based conversion coatings obtained by electrochemical tests were used for training three computational techniques (artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS), and support vector machine regression (SVMR)) based on Pretreatment-1 (acidic or alkaline cleaning: pH (1)), Pretreatment-2 (acidic or alkaline cleaning: pH (2)), and deposition time in the cerium bath as an input. Various statistical criteria showed that the ANFIS model (R2 = 0.99, MSE = 48.83, and MAE = 3.49) could forecast the corrosion behavior of a cerium-based conversion coating more accurately than other models. Finally, due to the robust performance of ANFIS in modeling, the effect of each parameter was studied

Three-Dimensional Thermo-Mechanical Elastic Analysis of Functionally Graded Five Layers Composite Sandwich Plate on Winkler Foundations

In this work, the first shear deformation theory (FSDT) is used for the thermo-mechanical analysis of a simply supported five-layer functionally Graded (FG) sandwich plate resting on a Winkler elastic foundation. The sandwich plate consists of five layers (two functionally graded face sheets (AL−AL2O3), with aluminum (Al) as the metal and Alumina (AL2O3) as ceramic phases. Two vinyl ester adhesive layers bond the face sheets to an Elastollan core. The governing equations are obtained using the principle of virtual displacements. A uniform distributed load q with constant magnitude is applied on the top face sheet while all layers experience a steady temperature equal to T. We adapted layerwise theory (LT) to solve each layer’s stress distribution. Navier solution is employed to produce the semi-analytical solution results, which are compared with those of three-dimensional finite element analysis obtained by ABAQUS software. A parametric study is presented to observe the effect of the material gradation, variation in plate dimensions, variation in the thermo-mechanical load, and elastic foundation on the deflections and stresses in the functionally graded sandwich plate. For a composite sandwich plate with mechanical load, in the absence of thermal load, results of the first-order shear layer theory obtained by using the Navire method are relatively good in comparison to the normal stresses obtained for investigated points, which are obtained by finite element

An Electrochemical Investigation of Nano Cerium Oxide/Graphene as an Electrode Material for Supercapacitors

In this paper, the effect of cationic and anionic ion sizes on the charge storage capability of graphene nanosheets is investigated. The electrochemical properties of the produced electrode are studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques in 3M NaCl, NaOH, and KOH electrolytes. Scanning electron microscopy (SEM) is used to characterize the microstructure and nature of the prepared electrode. The SEM images and X-ray diffraction (XRD) patterns confirm the layered structure (12 nm thickness) of the used graphene with an interlayer distance of 3.36 Å. The electrochemical results and the ratio of  confirm good charge storage and charge delivering capability of the prepared electrode in the 3M NaCl electrolyte. Charge/discharge cycling tests show a good reversibility and confirm that the solution resistance will increase after 500 cycles. In this paper, the effect of cationic and anionic ion sizes on the charge storage capability of graphene nanosheets, is investigated. Electrochemical properties of produced electrode are studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques, in 3M NaCl, NaOH and KOH electrolytes. Scanning electron microscopy (SEM) is used to characterize the microstructure and nature of prepared electrode. SEM images and XRD patterns confirm the layered structure (12 nm thickness) of the used graphene with an interlayer distance of 3.36 (Å). The electrochemical results and the ratio of q*O/q*T confirm a good charge storage and charge delivering capability of prepared electrode in 3M NaCl electrolyte. Charge/discharge cycling test shows a good reversibility and confirms that solution resistance will increase after 500 cycles

Free Vibrational Analysis of a Functionally Graded Five-Layer Sandwich Plate Resting on a Winkler Elastic Foundation in a Thermal Environment

The effect of adhesive layers bonding to the core of functionally graded (FG) surface layers is investigated using the free vibration of a five-layer sandwich composite plate resting on a Winkler elastic foundation in a thermal environment. It is assumed that all layers are experiencing a steady-state temperature ΔT. The layer-wise theory is used to derive the governing equations with the help of Hamilton’s principle. The Navier solution is employed to obtain the closed-form solutions. The numerical results obtained using the present theory are compared with three-dimensional finite elements implemented by ABAQUS software. The results show that the proposed theory is not only accurate but also efficient in predicting the natural frequencies of sandwich plates resting on Winkler foundations

Free Vibrational Analysis of a Functionally Graded Five-Layer Sandwich Plate Resting on a Winkler Elastic Foundation in a Thermal Environment

The effect of adhesive layers bonding to the core of functionally graded (FG) surface layers is investigated using the free vibration of a five-layer sandwich composite plate resting on a Winkler elastic foundation in a thermal environment. It is assumed that all layers are experiencing a steady-state temperature ΔT. The layer-wise theory is used to derive the governing equations with the help of Hamilton’s principle. The Navier solution is employed to obtain the closed-form solutions. The numerical results obtained using the present theory are compared with three-dimensional finite elements implemented by ABAQUS software. The results show that the proposed theory is not only accurate but also efficient in predicting the natural frequencies of sandwich plates resting on Winkler foundations

The effect of viscoelasticity on creep behavior of double-lap adhesively bonded joints

The effect of viscoelasticity of epoxy adhesive on creep behavior in the adhesive layer of a double-lap joint is studied in this paper. The joint is comprised of three elastic single isotropic adherend layers joined by an epoxy adhesive that is under shear loading. Prony series is used to modeling the relaxation modulus of epoxy adhesive. The differential equation is derived in Laplace domain, and numerical inversion from the Laplace domain to the time domain is achieved by the Fixed Talbot method. Results show that for an impulse load of 100N, maximum shear stress in the adhesive layer is reduced to 38% of its initial value after almost 12 days and 79% of its initial value over a very long time. The rate of increase in tensile load P has a direct effect on peak shear stress developed in the adhesive layer and holding P0 as a constant, increasing t p will lower the induced peak shear stress in the joint. Also, an increase in the thickness of the adhesive layer reduced the induced peak shear stress and strain in the joint