General-purpose Polyester Resin Research Articles

An investigation into mechanical properties of jute–polyester laminates for numerical prediction of strength and failure

AbstractThe study of natural fiber–based composites, which are being seen as a potential eco‐friendly alternative to popular synthetic fiber–reinforced composites, has, of late, gained considerable momentum. Replacing the latter composites is, however, an uphill task especially for advanced mechanical and structural engineering applications, which often require assessment of behaviors of materials and components numerically till failure. An implied scenario, for example, would be to design automotive body components using natural fiber–reinforced composites of sufficient strength for meeting crashworthiness requirements. In the current study, bi‐directionally woven jute fabric, due to its established supply base and consistent quality, has been chosen along with a general purpose polyester resin for fabrication of laminates of high fiber volume fraction obtained by combining the hand layup method with compression molding. A detailed and comprehensive mechanical characterization includes, for the first time, determination of tensile, compressive, shear, and flexural behaviors of jute–polyester laminates in a single unified study. The consistency of the generated mechanical properties, including deployment of secant moduli instead of conventional initial tangent moduli, in a finite element constitutive model is established by predicting the test‐based stress–strain or load–displacement behaviors and failure modes using a commercially available explicit nonlinear dynamic analysis code viz. LS‐DYNA.

Optimization of thrust force in drilling of carbon-basalt hybrid composites through Taguchi and RSM

The main object of the present work is to obtain better quality holes during drilling operation. Carbon-Basalt hybrid composite is a better performing composite with lesser price. For the present work, the hybrid composite test specimen was prepared by hand layup method. General purpose polyester resin is used as the matrix material. During the manufacturing process, alternate layers of carbon and basalt are stacked to prepare the composite. The maintained weight fraction of the fiber is 50%. The thickness of the obtained composite specimen is 6 mm. Delamination is the major reason for the rejection of drilled composites. The magnitude of delamination is directly proportional to the thrust force generated during drilling. Hence in the present work, an attempt has been made to reduce the thrust force to minimize the damage by optimizing the machining variables using Taguchi and RSM methods. The experiments were designed by DOE method. Taguchi’s 3 levels and 3 factors array was used to get the combination of parameters for each experiments. Totally 27 holes are drilled with different combinations of process parameters. The considered process parameters and their levels are: Drill diameter (6 mm, 8 mm & 10 mm), feed rate (50 mm/min, 75 mm/min & 100 mm/min) and spindle speed (750 rpm, 1000 rpm & 1250 rpm). Drilling process was carried out on a high precision CNC machine using HSS drill bits. The thrust force was measured by a Kistler dynamometer. Using ANOVA, the significant effect of considered parameters on the generated thrust force was also predicted. The result reveals that, the parameter feed rate has the most significant effect on thrust force, which is followed by the drill diameter. The least significant parameter is spindle speed. Both Taguchi and RSM methods suggest that, DD1, F1 and S3 combination parameters yields the lowest thrust value.

Modal study of trapezoidal cantilever plate like composite beam

The laminated composite beams are in use for various components in engineering applications. These beams are subjected to different environments and loads. The Dynamic analysis of composite components is essential to avoid the failure of the component. The component exhibits irregular behavior under certain working condition which can be analyzed by the natural frequency and mode shape. The complexity of the analysis of composite structures is faced as it often operates in complex environmental conditions and is frequently exposed to a variety of dynamic excitations. The orientation of the fiber layer also plays an important role on deciding the mechanical properties of the composite material. In this work a comparative modal analysis between specimen having rectangular and trapezoidal geometry is carried out. The effect of variation of taper angle and fiber orientations on natural frequency is studied. Bi directional woven Glass fiber is taken as reinforcement and general purpose polyester resin as matrix for the composite material of beams. The modal analysis of the specimen is conducted using finite element analysis using finite element analysis software.

Flexural, Tensile and Impact Properties of Alkali Treated Coir Fibre Composites Prepared by Compression Molding Technique

Polymeric materials reinforced with synthetic fibres such as glass provide advantage of high stiffness and high strength to weight ratio. Despite these advantages, the widespread use of synthetic fibre-reinforced polymer composite has a tendency to decline because of their high-initial cost and most importantly their adverse environmental impact. In this work, four different composites are prepared with untreated coconut fibres, NaOH mercerized coconut fibres, KOH mercerized coconut fibres and CSM glass fibres. A lot of studies are done earlier on NaOH mercerized coconut fibre composites. But, no studies are done specifically for KOH mercerized coconut fibre composites. So, KOH mercerized coconut fibre composites are prepared in this study. General purpose polyester resin is used for preparing all the compsites. The mechanical properties of composites are studied using the flexural test, impact test and tensile test. The mechanical properties of KOH mercerized coconut fibre composites are studied and compared with the mechanical properties of NaOH mercerized coconut fibre composites, untreated coconut fibre composites and CSM glass fibre composites.

Mechanical Properties of a Polyester Fibre Glass Composite

In the present work, mechanical properties of laminates fabricated by Hand lay-up technique using fibre glass (woven-mat) of density 3.6 N/m<SUP>2</SUP><SUP> </SUP>and general purpose polyester resin was investigated. Fibre glass polyester composite samples were fabricated with different fibre glass volume fractions (A-0.05, B-0.10, C-0.15, C-0.20, D-0.25 and E-0.30). The materials properties; ultimate tensile strength, Young’s modulus of elasticity, elastic strain, and impact strength of the materials were determined through standard tests on standard test samples. It was observed that the various mechanical properties (excluding the impact strength) were improved with increase in fibre glass volume and that the fibre glass- polyester composite is characterized by high toughness. It was concluded that the optimum fibre glass volume fraction for the composite is 0.25.

Synthesis and application of multilayered core shell particles for toughening of unsaturated polyester resin

Toughening particles, comprising two radially alternating rubbery and glassy layers, were prepared by using sequential emulsion polymerization. The conditions which led to controlled particle size and morphology are discussed. A relatively new type of inert core shell particle [fly-ash (FA)] and surface-activated FA, by two different silane coupling agents, namely 3-aminopropyltrimethoxy silane (AMP) and vinyltriethoxysilane (VES)-based multilayered toughening particles, which radially comprise rubbery and glassy layers, were also prepared. The toughening particles were used with general purpose polyester resin (GPR) for making composite sheets. Formation of multiple layers in the core-shell particles and their morphology were confirmed by transmission electron microscopy (TEM). The mechanical properties such as tensile, flexural, impact, and hardness of the toughened GPR are discussed critically. The tensile fractured surfaces were studied by scanning electron microscopy (SEM). Thermal property such as thermogravimetric analysis (TGA) were also discussed. The composites were exposed to various adverse environmental conditions such as water, boiling water, salt water, acid, alkali, toluene, weather, and freezing–thawing for 30 days. The mechanical properties (viz. the tensile strength, tensile modulus, elongation at break, flexural strength, flexural modulus, impact strength and hardness of FA/GPR, FA.AMP core/GPR, and FA.VEScore/GPR) were studied before and after exposure to adverse environmental conditions. The results indicate that the mechanical properties of FA/GPR composite are improved by surface treatment of FA and their resistance to the various environmental stresses is also enhanced substantially on modification by toughening particles. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 511–528, 2004

The influence of fibre treatment on the performance of coir-polyester composites

Surface modifications of coir fibres involving alkali treatment, bleaching, and vinyl grafting are made in view of their use as reinforcing agents in general-purpose polyester resin matrix. The mechanical properties of composites like tensile, flexural and impact strength increase as a result of surface modification. Among all modifications, bleached (65°C) coir-polyester composites show better flexural strength (61.6 MPa) whereas 2% alkali-treated coir/polyester composites show significant improvement in tensile strength (26.80 MPa). Hybrid composites comprising glass fibre mat (7 wt.%), coir fibre mat (13 wt.%) and polyester resin matrix are prepared. Hybrid composites containing surface modified coir fibres show significant improvement in flexural strength. Water absorption studies of coir/polyester and hybrid composites show significant reduction in water absorption due to surface modifications of coir fibres. Scanning electron microscopy (SEM) investigations show that surface modifications improve the fibre/matrix adhesion.

Acid Resistance of Glass Fibre Composites with Different Layup Sequencing: Part I-Diffusion Studies

The effects of sulphuric acid concentration and the sequential layup of glass fibre reinforcements on the diffusion behaviour of glass epoxy composite laminates were studied. In all, composites of six different resin systems viz., general purpose polyester, bis phenol-A polyester, vinyl ester, LY 556 epoxy, and MY 750 epoxy resins, reinforced with different layup sequencing consisting of chopped strand mat (CSM) and woven roving mat (WR) were exposed to sulphuric acid environments of different concentrations. The results of the study indicated that isophthalic polyester resin exhibited maximum resistance to sulphuric acid while general purpose polyester resin performed relatively inferior. The diffusion phenomenon became anamalous as the concentration of the sulphuric acid increased. Among the layup sequences considered, composite specimens with CSM as the skin layers exhibited higher weight gain than those with WR as the skin layers.

Chemorheology of thermosetting resins. I. The chemorheology and curing kinetics of unsaturated polyester resin

AbstractThe rheological properties and curing kinetics of a general‐purpose polyester resin have been determined during isothermal cure. Both steady and oscillatory shearing flow properties were determined using a cone‐and‐plate rheometer, and the curing kinetics were determined using a differential scanning calorimeter (DSC). It was found that, as cure progresses, the steady shear viscosity increases very rapidly with cure time at all shear rates investigated, and normal forces show negative values at low shear rates and positive values at high shear rates. The observed negative normal forces are believed to result from material shrinkage during cure, and positive normal forces from the deformation of large molecules, formed by crosslinking reactions during cure. Note that, in a cone‐and‐plate rheometer, the shrinkage force acts in the direction opposite to that of normal forces. It is, therefore, concluded that extreme caution is needed in the interpretation of normal force measurements with thermosetting resins, subjected to steady shearing flow. Dynamic measurements seem to offer some insight on the onset of gel formation. More specifically, we have found that, when the unsaturated polyester resin was cured at a fast rate, the time at which a maximum in the loss modulus G” occurs coincides reasonably well with the time tη∞ at which the steady shear viscosity η approaches infinity. However, at a slow rate of cure, the time at which tan δ equals unity agrees fairly well with tη∞. DSC measurement has permitted us to determine the degree of cure as a function of cure time and the kinetic parameters in an empirical expression for the curing kinetics advanced by Kamal and co‐workers. By combining the rheological and DSC measurements, we have constructed plots describing how the viscosity increases with the degree of cure, at various values of isothermal curing temperature.

Surface Weatherability of Glass-Fiber-Reinforced Polyester Sheeting. I. Effect of Modification of Resin Chemical Composition

An accelerated weathering test (2 to 0.67 cycle) has been applied to glass-fiber-reinforced polyester (GRP) to determine the effect on surface durability of modifiying the chemical composition of the resin matrix. The nature and rate of induced surface degradation were monitored by scanning electron microscopy. For GRP based on general purpose polyester resin (o-phthalic anhydride-propylene glycol-maleic anhydride-based) the nature of surface damage was not significantly influenced by chemical modification, although the time of initiation was altered. The average overall durability of GRP improved 60% by substitution of propylene glycol with neopentyl glycol, 30% by incorporation of a greater amount of maleic anhydride, and 20% by replacement of both anhydride and glycol with isophthalic acid and neopentyl glycol, respectively. By inference, replacement of anhydride with isophthalic acid reduced the durability of neopentyl glycol-based GRP by 40%.