bluuebunny/crossref_metadata_2025 huggingface dataset:
Styrene Crosslinked Vinylesters I: Correlation between the Theoretical Structure and Some Thermophysical Properties
Authors: Bellenger V. , Verdu J. , Ganem M. , Mortaigne B.
Published: March 2023

Six di or tetramethacrylates based on respectively bisphenol A diepoxides or phenol-epoxynovolacs were crosslinked by styrene in optimized conditions. Density, glass transition temperature, propagation rates of ultrasonic waves, tensile properties and rubbery modulus were then experimentally determined. A constitutive repeat unit of the network was written, on the basis of the hypothesis that the conversion of the styrene-methacrylate copolymerization was complete and that the resulting network was homogeneous. The relationships between the corresponding (theoretical) structure and the physical properties were then studied. Generally, the property values are in good agreement with theoretical predictions, except perhaps for tensile ultimate properties which appear lower than expected. It can be concluded that the true network structure is probably close to the ideal structure as assumed here.
Synthesis and Application of Phosphorylated Glucose in Flame Retardancy Finishing
Authors: Waly A. , El-Aref A.T. , Abdel-Mohdy F.A. , Zamzam N.E. , Hebeish A.
Published: March 2023

An organo-phosphorus compound, namely, phosphorylated glucose (PG) was synthesized. Four chemically modified cottons, namely, carbamoylethylated, acrylamidomethylated, cellulose carbamate, and cyanoethylated cotton bearing comparable amounts of nitrogen were also prepared. The effect of incorporation of PG into a finishing formulation containing Pyrovatex CP and etherified methylolated melamine (EMM) on flame-retardancy and other properties of these modified cottons was studied when the application was carried out under different conditions. The synergistic effect of N/P ratio was thoroughly investigated through an estimation of nitrogen and phosphorus contents and their impact on flame-retardancy properties, crease recovery, tensile strength and elongation at break of the finished cotton products determined.
Fibre Orientation Behaviour of Different Types of Glass Mat Reinforced Thermoplastics (GMT)
Authors: Meij A. , Munder O. , Neitzel M.
Published: March 2023

The mechanical characteristics of GMT strong depend on processing parameters. Processing simulation codes give satisfactory results on mould-filling, but not yet on fibre orientation and mechanical performance. This paper describes a method for quantifying fibre orientation in compression-moulded plates. Needled- and paper type-GMT blanks were moulded between parallel platens, inducing one- and two- dimensional flow fields. The fibre orientation was measured and compared to theories based on Jeffery's equation. Matching results were obtained for paper-type-GMT. Due to the different and complex orientation mechanism of needled-GMT, new mathematical models describing the orientation of this type of GMT need to be developed.
Grafting of Methacrylic Acid to Loomstate Viscose Fabric Using KMnO4/NaHSO3 System
Authors: EL-Rafie M.H. , Hafiz S.A. Abdel , Hassan S.M. , Hebeish A.
Published: March 2023

Potassium permanganate/sodium bisulphite redox system induced polymerization of methacrylic acid (MAA) with viscose fabric was studied under a variety of conditions. The polymerization reaction was studied with respect to graft yield, homopolymer, total conversion and graft efficiency. Results obtained indicated that increasing the MAA concentration, duration and temperature of polymerization enhances the graft yield, total conversion and homopolymer. Similar situations were encountered with KMnO 4 and NaHSO 3 concentrations but up to a certain limit after which these polymerization criteria decrease Meanwhile, the graft efficiency exhibits different maxima, depending upon the factors determining the polymerization reaction. Conversely, all the polymerization criteria decrease as the liquor ratio increases. A tentative mechanism for the polymerization reaction is also reported.
Radial Diffusion in a Sphere with Subsequent Change in Dimension. Desorption with a Finite Surface Coefficient of Mass Transfer in an Infinite Volume
Authors: Bakhouya-Sabbahi N. , Bouzon J. , Vergnaud J.M.
Published: March 2023

The liquid located in a polymer evaporates by following a process controlled by diffusion-evaporation. The general case when the desorption is followed by subsequent shrinkage is studied by considering a spherical polymer with a radial diffusion and a finite rate of evaporation. The volume of the surrounding is so large that it can be considered as infinite. The mathematical treatment is achieved, leading to general equations of radial diffusion and evaporation with a following change in dimension of the polymer. These general equations reduce to the Fick's equation when the amount of substance transferred is small enough. These general equations have no analytical solution, and the problem is resolved by using a numerical method with finite differences. The following parameters are of interest: the diffusivity, the coefficient of mass transfer on the surface, the radius of the empty bead, the relative volume expansion of the polymer due to the presence of the diffusing substance.
Electrical Properties of Solid Insulating Polymers by Thermally Stimulated Discharge Method
Authors: Vaezi-Nejad S.M. , Juhasz C.
Published: March 2023

The electrical phenomena in solid insulating polymers are intimately linked to their physical morphology and microstructure, their temperature and the time at which the observations are made with respect to time at which the stimulus was first applied. In this paper, the authors present a brief account of various transport mechanisms and the methods of investigation. Among several experimental techniques for investigation of electrical conduction, the decay methods, time of flight methods, and contact electrification are briefly described. This is then followed by a detailed description of thermally stimulated discharge technique for investigation of traps, space charges and dipole processes in polymers. In order to illustrate the usefulness of this technique, experimental results will be presented to demonstrate the existence of deep interface hole traps in double layer amorphous semiconductor photoreceptors.
Compressive Strength Retention of Impact-Damaged Laminates Containing Particulate Fillers
Authors: Yang Q. , Pritchard G.
Published: March 2023

The effect of six particulate fillers on the compressive strength of undamaged and damaged glass-epoxy laminates was studied. The intention was to determine whether, and how, the mechanical properties of the filled organic matrix could be correlated with the impact damage tolerance (expressed as compressive strength retention after impact) of fitted epoxy-glass laminates. Impact damage was induced by an instrumented falling weight device. The laminates contained solid glass beads, hollow glass microspheres, quartz, calcium carbonate, alumina trihydrate (ATH) and mica. The test results showed that all the fillers, apart from hollow glass microspheres, increased the tensile and flexural moduli of the fitted epoxy, and this in turn was accompanied by an improvement in the compressive strength of some of the undamaged lominates, but there was no positive correlation between the flexural modulus of the fitted matrix and the impact damage tolerance as reflected in compressive strength retention. In contrast there was a good correlation with matrix strength; i.e. a significant decrease in the compressive strength retention of impact-damaged laminates as the matrix flexural strengths were reduced by adding fillers. The pre-impact interlaminar shear strength of the laminates also correlated well with the compressive strength retention after impact.
Structural Relaxation of Poly(methyl methacrylate)
Authors: Avramov I. , Vassilev Ts.
Published: March 2023

The kinetics of structural, relaxation of poly(methyl methacrylate) (PMMA) is studied and it is shown that the activation energy of the process depends on the structural temperature Tf. A new method is proposed allowing the measurement experimentally of how the activation energy decreases with increasing Tf.

The dependence of the glass transition temperature Tg on the heating rate q+ is investigated for samples that were previously cooled down at a rate q = 12.5 K/min. It is found that the activation energy for structural relaxation is E = (250 ± 10%) kJ/mol at T=386K. On the other hand, the value of the apparent ”activation energy” obtained from the dependence of the structural temperature Tf on the cooling rate q- is considerably higher. This is an indication that the activation energy depends on Tf. We found that the temperature dependence of the activation energy of PMMA in the vitrification interval is E(T) = 250–670* (386/T-1) kJ/mol.
Sillicon Compounds as Factors Stimulating the Proliferative-Reparative Function of Connective Tissue and Modifying Reactogenicity of Polymeric Implants
Authors: Slutskii L.I. , Dombrovska L.E. , Sevastjanova N.A. , Shkirmante B.K. , Djakov V.M.
Published: March 2023

Initially, it was found that some representatives of silicon compounds, a new class of silicon organic compounds ‘monocyclic analogs of silatranes, - possess a biological activity which is expressed as a stimulation of the proliferative-reparative function of connective tissue. The. Silicon compounds which were tested accelerated wound healing and epithelisation in rats, they accelerated the evolution of dermal wounds caused by thermal burningas well. When included in the covering of subcutaneously implanted olive-shaped polyethylene devices, silicon compounds effectively stimulated development and maturation of granulation-fibrous capsules surrounding the implants.
Development and Characterisation of Composite Hydrophones
Authors: Tandon R.P. , Singh Ramadhar
Published: March 2023

Piezo components have been fabricated using lead zirconate titanate (PZT) and lead titanate (PT) as filler materials in a passive chloroprene rubber matrix. The temperature dependence of the dielectric parameters of PT composites has been studied. Effect of poling temperature and poling field on piezoelectric charge coefficient (d33) has also been examined in order to achieve optimum polarization. Three types of hydrophones were developed using solid PZT, PZT composite and PT composite. Their acoustic sensitivities have been presented over a frequency range 10–100 KHz. The hydrophone based on lead titanate composite exhibited the highest acoustic sensitivity (-202 dB re IV/mPa) which could find numerous applications in underwater acoustics.
Interferometric Studies on Polymer Fibres II. Application of Multiple-Beam Fizeau Method for the Characterisation of Multilayer Fibres
Authors: Hamza A.A. , Fouda I.M. , Sokkar T.Z.N. , Shahin M.M. , Seisa E.A.
Published: March 2023

A modified method using multiple-beam Fizeau fringes is used to measure refractive indices of immersion liquids. In this case, there is no need for making corrections for the temperature and dispersion of these liquids. This method is applied to determine the refractive index profile of a cylindrical multilayer fibre. A mathematical formula is derived in the case of the shape of multiple-beam Fizeau fringes crossing a cylindrical multilayer fibre, as well as equations to determine the refractive index profile for fibre having irregular cross section. Similar mathematical formulas are derived for the case of fibre having skin-core structure. This method with the derived equations is applied to determine the optical properties of “Terylene” and polypropylene fibres. Microinterferograms are given for illustrations.
Stacking Sequence Effect on Tensile and Fatigue Strength of Symmetric Laminates
Authors: Carroll M. , Ellyin F. , Kujawski D.
Published: March 2023

This paper presents the results of an experimental investigation into the tensile monotonic and fatigue behaviour of symmetric fibreglass-epoxy coupons using three ply angle orientations, 45°, -45° and 0° which were interchanged in three different configurations: [452, -452, 02]s, [452, 02, -452]s and [02, 452, -452]s. The results show that there is significant sequence effect on the monotonic strength and the fatigue performance. The monotonic results demonstrate an increase of 11% in the strength and 6% in stiffness between the weakest laminate, [02, 452, -452]s, and the strongest laminate, [452, -452, 02]s. The fatigue performance depends on lay-up and stress level. At higher stresses, the trend in stacking sequence effect on fatigue strength is the same as for monotonic loading. In contrast, at lower stresses the trend is opposite. The sequence effect observed in the monotonic and fatigue loading is discussed subsequently based on the numerical analysis of interlaminar stresses induced by the free-edge and constraint effect of 0° ply on damage development.
Phase Equilibria in Polymer/Solvent Systems. Part HI. Similarity between the Swelling of Polyurethane Gels in Water and the Water Absorption of Wood around the Ice Point
Authors: Hladik B. , Frahn S. , Borchard W.
Published: March 2023

Some aspects of the thermodynamics of swelling of polyurethane gels in the solvent water around 0°C are discussed. It is shown that the results obtained are very similar to the water sorption behaviour of plant cells or tissue in the same temperature range in a few cases.
Effect of Cooling Rate on the Energy Absorption Capability of Carbon Fibre/PEEK Composite Tubes
Authors: Hamada H. , Ramakrishna S. , Maekawa Z. , Sato H.
Published: March 2023

The primary objective of this work was to identify the effect of cooling rate on the energy absorption capabilities of carbon fibre/PEEK tubes. Thermoplastic composite tubes were fabricated using a thermally expandable PTFE mandrel technique. Three cooling rates were used: rapid-cooling (95.5°C/min.), gradual-cooling (8.2°C/min.) and slow-cooling (0.7°C/min.). The energy absorption characteristics were evaluated by axial compression of tube specimens between flat platens. All the composite tubes, independent of cooling rate, crushed progressively in splaying mode. The specific energy absorption capability of rapidly cooled tubes was 15% higher than that of gradually-cooled and slowly-cooled tubes. Efforts have been made to identify the factors which resulted in the superior energy absorption capability of rapidly cooled tubes.
Effects of Fibre Treatment on Fibre/Matrix Interfacial Bonding in Pinus Radiata Fibre/Thermoplastic Composites
Authors: Miller N.A. , Stirling C.D. , Van Tilburg V.S.M.
Published: March 2023

The effects of five different chemical treatments of Pin us Radiata fibres, produced by different pulping methods, on interfacial bonding between fibres and polyethylene and polypropylene have been investigated for composites produced by melt blending of fibre and polymer. The effects of adding a proprietary compatibiliser and a maleated polypropylene wax to the blend were also studied. The chemical treatments failed to give any improvement in tensile properties. Untreated fibres on their own and untreated fibres with addition of maleated polypropylene wax gave significant improvement in both tensile strength and stiffness. The lignin content on the surface of the fibres appeared to influence the degree of interfacial bonding in that fibres with low lignin surface content gave better results than fibres with high lignin on the surface.
Correlation between the State of Cure of Unsaturated Polyester Coatings and Their Resistance to Ethanol
Authors: Haffane N. , Benameur T. , Granger R. , Vergnaud J. M.
Published: March 2023

The correlation between the state of cure of an unsaturated polyester coating and its resistance to ethanol at room temperature is studied. The heat generated by the remainder of the cure reaction at a given time as a fraction of the total heat generated is called the state of cure. Sheets with various states of cure ranging from 75 to 95% were prepared and put in contact with an ethanolic solution at 95% ethanol. The process of ethanol absorption is controlled by transient diffusion with a constant diffusivity. A statement is obtained: the higher the state of cure, the lower the amount of ethanol absorbed and the lower the diffusivity.
Semi-Conducting Composites Containing a Ladder Polymer as a Conductive Filler
Authors: Bandara A.J. , Curley J.F.
Published: March 2023

This study is concerned with the use of a novel ladder polymer (SCL) as a conductive filler in insulating thermoplastics and thermosets. SCL, which had apristine electrical conductivity of 8.0 x 10-6 Scm-1, was mixed with poly(methylmethacrylate) (PMMA) and polyesters in various volume loadings in order to determine percolation behaviour. A maximum electrical conductivity of 1.2 x 10-8 Scm-1 was observed at loading of 13% v/v in polyester resin, while the maximum conductivity observed with PMMA was 7.3 x 10-7 Scm-1 at a loading of 11.2% by volume. The maximum conductivity was slightly lower for thin composite films of SCL/ PMMA. The thermal stability of the composite samples was found to be dependent upon the thermal stability of the host plastic since the composite showed decomposition behaviour characteristic of two separate phases. Thermal ageing of the composite samples at 100°C and 175°C showed that the electrical conductivities were stable at these temperatures over long periods of time. However, ageing at 250°C led to a decrease in electrical conductivity.
Environmental Effects in Composite Laminates with Voids
Authors: Müller de Almeida Sérgio Frascino , de Mas Santacreu Arthur Chaves
Published: March 2023

This work presents an experimental program aimed at investigating some aspects of environmental effects on carbon/epoxy laminates with voids. The objective is to obtain experimental data to subsidize acceptance criteria for ultrasonic inspection of composite parts for aerospace applications. A fabrication process that produces laminates with reasonably uniform distribution of voids and nearly constant fibre fraction is described. The interlaminar shear strength of laminates with three different levels of void content was measured at four different conditions: RTD (room temperature, dry), RTW (room temperature, wet), ETW (elevated temperature, wet), and LTW (low temperature, wet). Also, the possibility of extensive degradation of the laminate for a small number of thermal cycles was investigated. Since aerospace applications are considered, a group of specimens was submitted to four cycles of thermal shock between -54°C and 65°C. The experimental results are consistent with the fracture criterion for laminates with voids proposed by Almeida and Nogueira Neto. They postulated mat the presence of voids does not have detrimental effects on the laminate strength unless the void content is above a certain critical level. For laminates not submitted to thermal shock, it was concluded that humidity increases the laminate toughness but reduces its critical void content level. The effect of temperature is to decrease laminate toughness but increase the critical void content level. The four cycles of thermal shock between -54°C and 65°C only have a significant effect on the laminates in RTD condition. For this test condition, it has an effect similar to that of humidity, increasing the laminate toughness but reducing its critical void content level. After thermal shock, laminates under conditions RTD, RTW, and LTW had approximately the same interlaminar shear strength.
Synthesis of Poly(methacrylic Acid)-Cellulose Composites Using Different Cellulosic Materials in the Presence of Potassium Permanganate and Activator
Authors: El-Sisi F.
Published: March 2023

Polymerisation of methacrylic acid (MAA) in the presence of cellulose pulps prepared from bagasse, rice, straw and cotton stalk was carried out under a variety of conditions. Potassium permanganate (KMnO4) was used as initiator, along with either citric acid or sodium thiosulphate (Na2S2O3) as activator. The polymerisation products, including grafted cellulose, homopolymer, ungrafted cellulose and oxidised cellulose in a polyblended form, is called “composite”. Major factors affecting the polymerisation reaction were studied. These encompass initiator, activator and monomer concentrations, duration and temperature of polymerisation as well as the nature of the cellulose substrate. Results for the percent polymer yield of the composite and those of the total conversion of monomer to polymer suggest appropriate conditions for the synthesis of poly (MAA)-cellulose composite as: [KMnO4], 0 08%; [Na2S2O3], 2.5 m.mole L; [MAA], 100% based on weight of sample; material to liquor ratio, 1:30; temperature, 70°C and time, 60 minutes. The effect of the nature of the cellulose on the properties and characteristics of the composite could be realised from the following orders:

(1) for the polymer yield, graft yield and swellability: bagasse > rice straw > cotton stalk;

(2) for carboxyl content: bagasse > cotton stalk > rice straw; (3) for solubility: rice straw > cotton stalk > bagasse.
Review of Recent Developments in Poly(Phenylene Sulphide)
Authors: Cebe Peggy
Published: March 2023

An extensive review of recent developments in the synthesis, crystallization, structure and morphology of poly(phenylene sulphide) (PPS) polymers is presented. There has been a vast proliferation of knowledge about such thermoplastic matrix materials and the more important findings are now discussed, mainly for the literature period 1985 onward. New understandings have emerged about the amorphous phase and its impact on polymer properties. Considerable data have been reported on the thermal properties of PPS too. PPS is expected to hold its position as one of the more important thermoplastics and to attract further research interest.
Image Analysis Method for Estimating 2-D Fibre Orientation and Fibre Length in Discontinuous Fibre Reinforced Composites
Authors: Pourdeyhimi B. , Ramanathan R.
Published: March 2023

In discontinuous fibre reinforced composites (DFRC), the fibre length and orientation influence greatly the ultimate physical and mechanical properties of the material.

A number of attempts dealing with methods for measuring fibre orientation are reported in the literature. These methods however, are unable to characterize fibre length. Fibre length may be affected by the type of processing involved.

This study reports on the use of image analysis techniques for determining both fibre orientation and length. To verify the accuracy of the methods used, simulated images with known characteristics are used.
Influence of Loading Mode and Hydrothermal Environment on the Contribution of the Interface to the Cohesion of Glass/Epoxy Composites
Authors: Krawczak Patricia , Pabiot José
Published: March 2023

The aim of this paper is to make clear the way the interface contributes to the cohesion of the composite by means of several macroscopic characterization methods (interlaminar shear strength, transverse tension with monitoring of acoustic emission, mode I and mode II fracture mechanics). The paper highlights the main parameters of influence, in particular the loading mode and the hydrothermal environment. Moreover the study made it possible to recommend certain characterization methods for the interface based on the variations in mechanical and physical parameters.
Effects of Cure History on Residual Stresses in Epoxy Resins
Authors: Wang Hong-bing , Yu Tong-yin
Published: March 2023

By studying the residual cure stresses for various temperature-cycles and time-cycles of epoxy resins, we find mat the stresses depend on the competitive process between the subsequent curing and annealing. The residual stresses increase with extent of cure, but decrease with increasing stress relaxation. Changing the curing history alters the residual stresses.
Graft Copolymerization of 2-Vinyl Pyridine and Styrene onto Isotactic Polypropylene Fibres by Pre-irradiation
Authors: Kaur Inderjeet , Kumar Sunil , Misra B.N.
Published: March 2023

In an attempt to modify isotactic polypropylene (IPP), the graft copolymerization of 2-vinyl pyridine (2-VP) and styrene has been studied by preirradiation in air in aqueous media. The percentage grafting (Pg) has been studied as a function of different reaction parameters and optimum conditions for grafting have been determined. The rate of grafting (Rg) of 2-VP and styrene has been evaluated as a function of (i) total dose, (ii) initial monomer concentration, and (iii) temperature. The graft copolymers have been characterized by thermal analysis. The dyeing behaviour of the graft copolymer has also been studied.
Influence of Compatibilizer and Additives on the Mechanical Properties of Polyethylene-Polystyrene Blends
Authors: Simitzis J. , Paitontzis C. , Economides N.
Published: March 2023

Polymer blends were prepared based on three different types of LDPE (A.B.C) and polystyrene without or with compatibilizer (KRATON G-1652) and with the addition of a pigment Iriodin, for the improvement of the optical properties. The Brabender torque and the tensile properties of the polymer blends were determined, particularly, the yield stress σy, the ultimate tensile strength (e.g. the strength at break) σB and the ultimate elongation (elongation at break) εB. By factorial experimental design, factors A (proportion of LDPE/polystyrene) and B (proportion of compatibilizer) were found to be statistically significant while C (type of LDPE) has lower significance. The compatibilizer acts as a reinforcing agent in the polymer blend of LDPE and polystyrene, changing the stress-strain curve to a ductile behaviour, increasing the torque, σB and εB and decreasing σY. Graphite, which is contained in LDPE-A, acts as a reinforcing agent. Iriodin does not act as a reinforcing agent in the polymer blend but leads to a decrease of σB, and to an increase of torque. It does not influence the stress-strain curve much. The appropriate amount of compatibilizer is determined to be up to 20%. Iriodin improves the optical properties of polymer blends and compensates for their inferior mechanical properties.
Diffusion of Aromatic Liquids into Blends of Ethylene-Propylene Copolymers and Isotactic Polypropylene Membranes
Authors: Aminabhavi Tejraj M. , Phayde Hemant T.S. , Ortego J. Dale
Published: March 2023

The molecular transport of benzene, toluene, p-xylene, ethylbenzene, chlorobenzene, 1,2-dichlorobenzene, and mesitylene into miscible polymeric blends of ethylene-propylene random copolymer and isotactic polypropylene has been investigated at 25, 40, 55, and 70°C. For all liquids, the solvent transport rate, equilibrium uptake and degree of penetrant overshoot are influenced by the nature of the solvent molecules and by the temperature. Sorption- desorption-resorption-redesorption (S-D-RS-RD) experiments have been carried out to determine the sorption equilibrium and diffusion coefficients. These S-D-RS-RD experiments are a convenient way of studying the weight loss, if any, during the long-term solvent exposure, which may be associated with the release of residuals. The activation parameters for diffusion, permeation, and sorption have been obtained. The concentration dependence of diffusivity has been studied. The morphology of the membrane material has been investigated using XRD and scanning electron microscopy.
Viscoelastic and Mechanical Properties of Epoxy/Mixed Amine Systems. Influence of Stoichiometry and Cure Conditions
Authors: Garmendia J. , Alcorta C. , Llano-Ponte R. , Mondragon I. , Rubio A.
Published: March 2023

Epoxy networks based on the diglycidyl ether of bisphenol A (DGEBA) and a mixture of an aliphatic triamine and a difunctional cycloaliphatic diamine were studied. The glass transition temperatures of mixtures with different stoichiometric ratios were analysed by differential scanning calorimetry and dynamic mechanical techniques. The influence of the cure schedule was also studied for all mixtures, post-cured and not fully cured. Differences in crosslink densities were studied in the glass transition region. By using the average molecular weight between crosslinks, calculated using the rubber elasticity theory, the correlation between the glass transition temperature of cured systems and that corresponding to the unreacted system was determined. The variation of the glass transition temperatures was interpreted in terms of the macromolecular chain motions. Flexural properties such as modulus, strength, and strain to break were measured for the post-cured mixtures with different stoichiometrics.
Effects of Structure and Microcracks on Fatigue Properties of Three-Dimensional Composites
Authors: Chou Shen , Chen Hong-En
Published: March 2023

Three-dimensional carbon fibre/epoxy resin composites were prepared, which had either three-axis or five-axis carbon fabrics (3D-3A and 3D-5A) in four weave gauges, and were embedded with PTFE film in the fabric structures to initiate various types of microcracks. The flexural fatigue properties of these 3-D composites were studied. The results show that the flexural properties and fatigue life of 3D-3A are higher than those of 3D-5A. Enlarging the weave gauge of 3D-3A and 3D-5A enhances the flexural properties, fatigue life and resistance to fatigue crack growth. The 3D-3A with a weave gauge of less than 5 mm or the 3D-5A with a fatigue stress lower than 140 MPa has a considerably higher ability to resist fatigue in presence of PTFE film. Under 120 MPa stress, both 3D-3A and 3D-5A retain more than 70% residual flexural breaking strength. However, with PTFE film embedding, their stiffness reduces significantly. A crack in 3D-3A grows along the Z-axial bundle, whereas a crack in 3D-5A grows in the X-Y plane. The 45°-axial bundle shows a pull-out phenomenon.
Epoxy Resin - Cyclic Carbonate Oligomer Compositions Cured with BF3·Et2O
Authors: Rokicki Gabriel , Nguyen Thinh X.
Published: March 2023

The properties of bisphenol A epoxy resins containing bidentate cyclic carbonate oligomers cured with BF3 complexes by cationic polymerisation are presented. The effect of cyclic carbonate content on the gel time, peak exotherm temperature and degree of crosslinking of the epoxide-cyclic carbonate compositions were investigated. It was found that for the range of 0–30 wt. % the amount of energy released during crosslinking rises with increasing cyclic carbonate concentration. The reaction mechanism, and the reason for the higher enthalpy of polymerisation of epoxide-cyclic carbonate compositions in comparison with the epoxy resin, are discussed. The cured compositions exhibited good mechanical properties, especially the impact resistance and the tensile strength.
The Percolation Concept and the Electrical Conductivity of Carbon Black-Polymer Composites. 2: Amorphous Chloroprene Rubber Mixed with HAF Carbon Black
Authors: Ali M.H. , Abo-Hashem A.
Published: March 2023

The concentration and temperature dependence of the electrical conductivity (a) of amorphous chloroprene rubber CR mixed with high abrasion furnace (HAF) carbon black was investigated. It was found that the concentration dependence of a satisfied the scaling law of percolation clusters [σ = σo (P-Pc)β] through the range of Pc ≤ P ≤ 0.43 where Pc is the percolation threshold, P is the carbon concentration and β is the exponent (relates to the cluster size). The difference between the value of β obtained and that given by the scaling law was attributed to the occluded rubber which acts as if it were carbon rather than matrix. The occupation number (Z) was found to be 8.2 as calculated from the percolation threshold. The correlation between β and Z was found to be β = Z + 1. It was also found that the filling factor for HAF carbon was 0.70, which is the mean of the values for random close packed spheres and uniaxial simple cubic packed rods.

Conductivity was thermally activated below the percolation threshold. Above it, the variation of σ with temperature was attributed to the breakdown and reformation of carbon clusters with temperature.
The Percolation Concept and the Electrical Conductivity of Carbon Black-Polymer Composites. 3. Crystalline Chloroprene Rubber Mixed with FEF Carbon Black
Authors: Ali M.H. , Abo-Hashem A.
Published: March 2023

The filler concentration and temperature dependence of the electrical conductivity (a) of crystalline chloroprene rubber CR (Butaclor 41H) mixed with fast extrusion furnace (FEF) carbon black was investigated. It was found that the percolation concept held true for these composites, where σ shows a fairly sharp increase when the mass fraction of FEF carbon black in the mixture exceeds 20%. The estimated values of the filling factor (f) and the occupation number (Z) were found to be 0.82 and 8.2 respectively. The scaling law for percolation clusters [σ = σo (P - Pc)β] was valid within the range Pc ≤ P ≤ 0.34 and the estimated value of the exponent β was 6.8, where P = concentration of filler and Pc = the critical concentration.

The conductivity was thermally activated below and at the percolation threshold, with the same activation energy. The decrease in c with temperature (followed by a subsequent increase above a certain temperature) was attributed to the phase transition of CR (41H) and to the change in size of the carbon black clusters from infinite to finite with temperature.

In the more highly loaded compounds, the temperature dependence of σ was controlled by the breakdown and reformation of carbon clusters with temperature.
Composite Lamination to Wood
Authors: Pidaparti R.M.V. , Johnson K.
Published: March 2023

In order to enhance the stiffness and strength characteristics of wood, hybrid laminates consisting of spruce wood with (a) graphite-epoxy and (b) polyester-glass cloth were made. These hybrid laminates were tested for tension, three-point bending and cantilever bending to estimate the effectiveness of the lamination. The results obtained suggest that using graphite-epoxy lamination rather than wood significantly increased the stiffness compared to the polyester-glass, but did not increase the failure load capabilities in three point bending.
Novel Bismaleimide - Epoxy Resin System: III
Authors: Patel Hasmukh S. , Patel Nilesh P.
Published: March 2023

Novel diamines, namely N,N′-bis[1-(4-aminophenyl) ethanonyl]-4,4′-(1,1′-biphenyl)diamine (DA1), N,N′-bis[1-(4-aminophenyl) ethanonyl]-4,4′-(1,1′-biphenyl methane) diamine (DA2) and N,N;-bis[1-(4-aminophenyl) ethanonyl]-4,4′-(oxybisphenyl)diamine (DA3) have been prepared and reacted with various bismaleimides (BM) at a BM: diamine ratio of 1:2. The resulting oligoimides have been characterized by elemental analysis, IR spectral studies, and thermogravimetry. Their number average molecular weights ([Formula: see text]n) were estimated by nonaqueous conductometric titration. All of the oligoimides have been used as curing agents for epoxy resins based on the diglycidyl ether of bisphenol-A, and studied by differential scanning calorimetry (DSC). Glass and carbon fibre reinforced composites have also been prepared and characterized by mechanical properties.
NDT of Composite Materials - Problems and Solutions 3. Modelling of Dielectric Relaxation Phenomena
Authors: Matiss I.
Published: March 2023

This paper discusses the modelling of frequency dependent dielectric relaxation as a support for designing transducers, the optimisation of testing conditions, identification of the internal structure of heterogeneous media, evaluation of errors and development of software for expert systems, etc. Basic principles, and the main models for relaxation behaviour are described. In this way it is possible to calculate the frequency dependence of the complex dielectric permittivity of various two- and three-component structures if the frequency dependence of the components is known.
Miscibility of Tertiary Amide Polymers with Poly(styrene-co-acrylonitrile)
Authors: Yeo Y.T. , Goh S.H. , Lee S.Y.
Published: March 2023

The miscibility of poly(N-vinyl-2-pyrrolidone) (PVP), poly(N-methyl-N-vinylacetamide) (PMVAc) and poly(N,N-dimethylacrylamide) (PDMA) with poly(styrene-co-acrylonitrile) (SAN) was studied. The three tertiary amide polymers are miscible with SAN, having a sufficiently high acrylonitrile (AN) content. The critical AN contents are 62, 65 and 68 wt% for PVP, PMVAc and PDMA, respectively. The miscibility behaviour is discussed in terms of a binary interaction model.
The Damage Tolerance of Fire-Retardant Glass-Epoxy Laminates
Authors: Yang Qiang , Pritchard G. , Phipps M.A. , Rose R.G.
Published: March 2023

Alumina trihydrate is an effective and widely used fire retardant and smoke suppressant, with several other incidental advantages, but it usually lowers the mechanical strength of thermosetting resins and laminates. This paper reports the extent of the reduction in the impact damage tolerance of glass-epoxy woven roving laminates, when measured by determining their compression strength retention after impact (CAI). Inserting aramid plies reduced rather than increased the damage tolerance at low impact energies, regardless of their position. Tentative reasons for this observation are offered. Other material changes were also investigated. The benefit of using a rubber toughening modifier (Hycar ATBN) in the epoxy matrix was confined to the lowest impact energy range. Changing the epoxy resin curing agent from a cold curing, mixed amine system to a hot curing piperidine one resulted in an improved compression strength before impact, and in some cases also an improvement in post-impact strength retention.
A Review of Microporous Composite Polymeric Membrane Technology for Air-Separation
Authors: Chung Tai-Shung
Published: March 2023

A detailed review of the fabrication technology of microporous composite polymeric membranes has been conducted. We believe that this type of membrane has greater potential than the traditional asymmetric-composite membranes to be used for the development of the third generation of gas-separation membranes. However, there are four major challenges when preparing a high-performance microporous composite membrane: namely, eliminating pore intrusion, reducing coating thickness, improving interfacial adhesion and enhancing separation performance. In this article, we review and identify those approaches that have overcome or can potentially overcome these difficulties.
Electro-Mechanical Properties of Conductive Epoxy Composites
Authors: Strümpler R. , Maidorn G. , Garbin A. , Ritzer L. , Greuter F.
Published: March 2023

The electrical resistivity of epoxy composites was studied during curing and heating of the cured material. The initial resistivity ρ of epoxy containing a metallic filler was in the range of 106 to 107 Ωm. During curing a sudden reduction of ρ by eight orders of magnitude was observed. The shrinkage of the polymer during cross-linking and the build-up of internal stresses results in a lower inter-particle contact resistance. The contraction can be reversed by heating up again. Around the curing temperature, the resistivity increased by six to eight orders of magnitude due to the expansion of the material. The resistivity increased progressively until the contacts between the particles were opened and the composite reached a high-ohmic state.
Simulation and Measurement of Reinforcement Deformation during Preform Manufacture
Authors: Long A.C. , Rudd C.D. , Blagdon M. , Kendall K.N. , Demeri M.Y.
Published: March 2023

The use of liquid moulding processes including resin transfer moulding (RTM) and structural reaction injection moulding (SRIM) is now becoming increasingly popular in the automotive industry. These processes involve the injection of liquid resin into a fibre preform, which may be comprised of several layers of reinforcement mats or fabrics. Structurally demanding applications usually rely on “zero-crimp” engineered fabrics consisting of two or more groups of fibres stitched together using embroidery techniques. Preform manufacture usually involves a matched mould forming process, in which layers of reinforcement are formed between rigid tools to the component geometry. This requires a degree of fibre movement and re-orientation which can have a significant effect on the resulting processing and mechanical properties. This paper describes the development of a kinematic deformation model to predict the distribution of fibres within the preform. An automatic strain measurement system is used to characterise fabric deformation, enabling the fibre orientations within three-dimensional preforms to be determined. This is applied to a number of generic geometries with increasing depth of draw, allowing the deformation characteristics of reinforcement fabrics to be established and testing the validity of the process model.
Stress, Holes and Chemicals: Environmental Effects on Carbon Fibre Reinforced PEEK Laminates
Authors: Pritchard Geoffrey , Randies Steven J.
Published: March 2023

Carbon fibre/PEEK laminates were immersed in several liquid chemical environments including aviation jet fuel, water, Skydrol hydraulic fluid, and dichloromethane. They were simultaneously subjected to tensile, flexural and (in some cases) compressive loads. Comparison experiments were performed with samples in dry air. The rate of sorption of the liquid environments into quasi- isotropic laminates containing small circular holes was studied as a function of the (constant) strain applied. The specimens were then broken in tension. Strength and modulus retention were noted. The nature and magnitude of the load and of the environment had little effect on the failure mode, but considerable effect on the strength retention, and damage was sometimes initiated in the vicinity of the holes. Critical strain levels for damage initiation in dichloromethane are reported. A few results are also reported for unidirectional laminates, without holes.
Elastic Behaviour and Damage of Three-Dimensional Woven Fabric Composites
Authors: Kuo Wen-Shyong
Published: March 2023

The goal of this research was to investigate the elastic properties and damage behaviour of three-dimensional woven fabric composites. Transformed stiffness and compliance matrices have been obtained in closed-form expressions for orthotropic materials. We introduced three orthotropic constants which enable the transformation to be greatly simplified. A deformation model has been established based on the force equilibrium of a slice of a fabric. Two three-dimensional woven fabrics with different weaving structures and yarn cross-sections were examined. Experiments have been conducted for the three-axis fabrics. Comparisons have been made between experimental and analytical results. The damage mechanisms due to tensile and flexural loads have been observed. In both loading cases, defects around the through-the-thickness yarns have been found to be critical in crack initiation. Being the crack initiators, these defects can be detrimental to the in-plane properties.
Electron Beam Initiated Grafting and Crosslinking of Ethylene Vinyl Acetate Copolymer. Part II: Mechanical and Electrical Properties
Authors: Datta Sujit K. , Chaki Tapan K. , Khastgir D. , Bhowmick Anil K.
Published: March 2023

Mechanical, dynamic mechanical and electrical properties of electron beam modified ethylene vinyl acetate (EVA) copolymer in presence of trimethylolpropane trimethylacrylate (TMPTMA) and triallyl cyanurate (TAC) as sensitizer have been described. The tensile strength of the TMPTMA modified EVA increases with increase in radiation dose up to a certain level due to the development of network structure, while it does not change significantly for the TAC based system due to poor stress transfer. The tensile strength deteriorates sharply at higher radiation doses because of the predominating effect of breakdown of the network structure. However, the tensile strength changes marginally with TMPTMA level and decreases with an increase in TAC level. DMTA studies indicate mainly two transitions (namely γ and α) in the order of increasing temperature for both TMPTMA and TAC based samples. The γ-transition temperature shifts to higher values and the α-transition shifts to lower values with an increase in radiation dose due to modification of the main chain and to a decrease in crystallinity. Dielectric analysis shows a sharp transition at around -20°C for all uncured and cured samples due to movement of the highly polar acetate groups present in EVA. The loss factor decreases sharply at high temperature with increase in radiation dose due to crosslinking.
A Study of Blends of Poly(ether ether ketone ketone) and Poly(ether sulphone): Effect of the Addition of Poly(ether ether ketone) Oligomer
Authors: Shibata Mitsuhiro , Fang Zhijie , Yosomiya Ryutoku
Published: March 2023

The thermal and viscoelastic behaviour and mechanical properties of blends of poly(ether ether ketone ketone) (PEEKK) with poly(ether sulphone) (PES) have been investigated. Additionally, poly(ether ether ketone) (PEEK) oligomer was added as the third component to the above blend in order to improve its compatibility and mechanical properties. From the results of viscoelastic measurements and differential scanning calorimetry (DSC) for the blends of PEEKK with PES, it was revealed that the blends are partially compatible systems, especially at low levels of PES, and their storage modulus at around 200°C rises as the PES content increases. When PEEK oligomer was added to the PEEKK/PES blend as a third component, its compatibility and flexural strength were considerably improved. This was consistent with SEM micrographs of the blends. Concerning the crystallisation behaviour, although the melting point (Tm) and crystallisation temperature (Tc) were almost constant values regardless of the PES content of the blends of PEEK/PES, Tm and Tc were lowered as the PEEK oligomer content increased for the blends of PEEKK/PES/PEEK oligomer.
Rheology and Removability of New Sizing Agents Based on Polyvinyl Alcohol
Authors: El-Sisi F.
Published: March 2023

Two synthetic sizing agents based on polyvinyl alcohol (PVA) were prepared by direct radiation of acrylic acid (AA) or N-vinyl-2-pyrrolidone (VP) in the presence of predissolved PVA. The rheology, film resolubility and removability of these sizing agents were compared with those of PVA. It was found that (a) the flow behaviour of 10% aqueous solutions (at 80°C) of these materials is characterized by a non-Newtonian thixotropic property that shows a measurable shear thinning character, (b) the degree of thixotropy is arranged ascendingly according to the order PVA/PVP < PVA/PAA < PVA, (c) the solubility rate of PVA size films and size removability of these sizing agents (as a function of the nature of the size used) follow the decreasing order: PVA/PVP > PVA/PAA > PVA.
The Development and Appraisal of 3D Interlinked Woven Structures for Textile Reinforced Composites
Authors: Hill B.J. , McIlhagger R.
Published: March 2023

A method, based on simple geometry, is devised to predict the percentages of fibre in the three mutually perpendicular directions for 3D woven interlinked structures. This provides an opportunity to design fabrics for specific applications which have known amounts of fibre in the principal stress direction.
Phase Behaviour of Blends of poly(chlorinated-ethyl methacrylate) with poly(styrene-co-aciylonitrile) and with poly(p-methylstyrene-co-acrylonitrile)
Authors: Goh S.H. , Lee S.Y. , Low S.M. , Peng Jiande , Ni Xiping
Published: March 2023

The phase behaviour of blends of four poly(chlorinated-ethyl methacrylates) with poly(styrene-co-acrylonitrile) (SAN) and with poly(p-methylstyrene-co-acrylonitrile) (pMSAN) was studied. Poly(1-chloroethyl methacrylate) and poly(2,2-dichloroethyl methacrylate) are miscible with SAN and pMSAN over a certain copolymer composition range, showing miscibility windows. Poly(2,2,2-trichloroethyl methacrylate) (PTCEMA) is miscible with SAN and pMSAN having high acrylonitrile contents, showing miscibility doors. PTCEMA is also miscible with polyacrylonitrile. However, poly(1,2,2,2-tetrachloroethyl methacrylate) is immiscible with any of the SAN and pMSAN samples.