Flexural Modulus Of Composites Research Articles

Water aging effects on the flexural properties of fully biobased coir fiber composites

AbstractThis work describes the flexural behavior of biocomposites composed of a polyurethane matrix derived from castor oil plants and coir fibers. A statistical design is performed to identify the effects of fiber alkaline treatment and aging on the flexural modulus and strength of the composites. Physical tests and failure analyses are carried out to better assess their mechanical performance. A second experiment at 100% relative humidity is performed on treated fiber composites to compare with those obtained by immersion in water. The flexural modulus of the composites is not significantly affected by the fiber alkali treatment, while the strength is reduced by 35.17% when treated fibers are considered. Increasing the exposure time of composites under both aging conditions progressively reduces their flexural properties. The aging process of biocomposites in an environment with 100% relative humidity takes twice as long to reduce to the same flexural properties as those aged in water.Highlights Composites made with treated fibers showed higher apparent density and lower porosity. Water aging reduces flexural modulus and strength of biobased coir composites. The bending properties are strongly dominated by the properties of biobased polymer. 100% relative humidity takes twice as long to reduce to the flexural properties as those aged in water. Untreated coir fibers achieve superior bending properties under moisture aging.

Effect of NaOH Treatment on the Flexural Modulus of Hemp Core Reinforced Composites and on the Intrinsic Flexural Moduli of the Fibers.

This paper describes the potential of using hemp core waste in the composite industry. These lignocellulosic residues can be used to produce environmentally friendly and economically viable composites and improve the overall value chain of hemp production. To this purpose, hemp core residues were alkaline treated at different NaOH concentrations and then mechanically defibrated. Hemp core fibers were mixed with polypropylene and injection molded to obtain testing specimens. The effect of sodium hydroxide on the flexural modulus of composites was studied from macro and micro mechanical viewpoints. Results showed remarkable improvements in the flexural modulus due to the presence of hemp core fibers in the composites. At a 50 wt % of reinforcement content, increments around 239%, 250% and 257% were obtained for composites containing fibers treated at a 5, 7.5 and 10 wt % of NaOH, respectively. These results were comparable to those of wood composites, displaying the potential of hemp core residues. The intrinsic flexural modulus of the hemp core fibers was computed by means of micromechanical analysis and was calculated using the ratios between a fiber flexural modulus factor and a fiber tensile modulus factor. The results agreed with those obtained by using models such as Hirsch and Tsai–Pagano. Other micromechanical parameters were studied to fully understand the contribution of the phases. The relationship between the fibers’ intrinsic flexural and Young’s moduli was studied, and the differences between properties were attributed to stress distribution and materials’ anisotropy.

Appraisal of mechanical properties of different particle sizes of palm kernel shell, coconut shell and mixed palm kernel-coconut shells particles epoxy-filled composites

This study presents the appraisal of indentation hardness and flexural modulus of composites prepared by mixing particles of palm kernel shell (PKS), coconut shell (CNS) and mixtures of palm kernel-coconut shell (MPKCNS) of different sizes (35.5 μm, 75 μm and 106 μm) with epoxy and hardener for various applications. The Rockwell hardness tester results showed that PKS particles epoxy filled composites of 35.5 μm had the highest hardness number of 77 while the MPKCNS particles epoxy filled composites of 106 μm had the least hardness number of 43. The CNS particles epoxy filled composites of 35.5 μm and 75 μm had relatively higher flex moduli of 428.66 MPa and 425.55 MPa respectively. The particle size of 106 μm had relatively higher flexure extension than 35.5 μm and 75 μm. The Scanning Electron Microscope (SEM) analysis revealed proper adhesion of the shell particles and epoxy resins with little or no pores in the composites. The PKS particles epoxy filled composites of 35.5 μm can be employed to enhance the mechanical properties of the composites for engineering applications.

Submicron inorganic particles as an additional filler in hybrid epoxy matrix composites reinforced with glass fibres

In this study, the effect of selected submicron metal oxide (zinc oxide, titanium oxide) or non-metal oxide (silicon dioxide) particles on mechanical and thermo-mechanical properties of epoxy/glass composites was investigated. The applied epoxy resin was a diglycidyl ether of bisphenol-A cured with triethylenetetramine. As a reinforcement twill weave E-glass fabric was used. Hybrid composites (contained particulate and fibrous filler) were fabricated by using the hand lay-up method and the average content of glass fibres was 39–41 wt%. Flexural properties, thermo-mechanical properties, abrasion resistance and hardness were determined for each group of the prepared hybrid epoxy/glass composites. The obtained results were compared with control samples (without submicron particles). Investigations showed that the addition of 2 wt% SiO2, 4 wt% TiO2 or 4 wt% ZnO to epoxy resin improved the flexural strength and the flexural modulus of composites. Dynamic mechanical analysis showed that the addition of the mentioned particles enhanced storage and loss modulus. It can be attributed to the good dispersion and good interaction between submicron-mentioned particles and the epoxy matrix.

A Novel Sustainable Design to Develop Polypropylene and Unsaturated Polyester Resin Polymer Composites From Waste of Major Polluting Industries and Investigation on Their Physicomechanical and Wear Properties

A novel concept of using Nutraceutical Industrial Coriander Seed Spent (NICSS) and Congo red (CR) dye adsorbed onto NICSS (CR‐NICSS) as filler materials to fabricate polypropylene (PP) green thermoplastic composites and unsaturated polyester resin unsaturated polyester resin (USP)/CR‐NICSS and USP/NICSS composites is presented. To maximize the adsorption of CR on NICSS and to study the influence of five parameters viz, process time, temperature, initial concentration of dye, adsorbent dosage and pH of the reaction mixture, we use a two‐level fractional factorial design approach and analysis of variance to develop statistical model. The composites were evaluated for physico‐mechanical and tribological properties and compared with the thermoplastic composites fabricated using NICSS. Flexural strength and flexural modulus of composites were improved by adding CR‐NICSS and NICSS into PP matrix. The abrasive wear behavior, wear volume loss and specific wear rate as a function of abrading distance at 150, 300, 450, and 600 m and different loads of 23.54 and 33.54 N at 200 rpm were determined. The water absorption characteristics of thermoplastic composites were studied. The surface morphology of tensile fractured PP/CR‐NICSS was examined under scanning electron microscope. The influence of water and thermal ageing on tensile strength and physical properties, such as density, surface hardness and effect of chemicals on USP/CR‐NICSS and USP/NICSS are reported. POLYM. COMPOS., 40:1142–1157, 2019. © 2018 Society of Plastics Engineers

Mechanical and thermal insulation properties of elium acrylic resin/cellulose nanofiber based composite aerogels

For the first time, recyclable Elium® resin was used to dip-coat freeze-dried cellulose nanofibers (CNF) aerogel to obtain recyclable composite materials. TGA allows showing that the obtained material is less hydrophilic than the neat aerogels. The SEM analysis revealed that the CNF aerogel porosity was reduced after adding Elium® resin. It has a direct impact on the material mechanical and thermal properties. For the mechanical point of view, the results confirm that Elium® resin drastically improve the new material flexural properties. The Elium® resin, via crosslinking with the CNF aerogel, increases the composite flexural modulus and strength by at least one order of magnitude compare to the CNF aerogels. Concerning thermal properties, the degradation temperature of the Elium/CNF composite materials is about 90 °C above that of neat CNF aerogels improving the resistance of the composite material against high temperatures. The effective thermal conductivity increases as the pores are filled with the resin, inducing an increase of the solid conductivity contribution. Starting from CNF aerogels having a thermal conductivity around that of air (λ=0.025 W/(m.K)), the final composite thermal conductivity increased up to 0.1 W/(m.K). However, it can still be considered as a thermal insulator according to French regulations (λ≤ 0.1 W/m.K). Overall, this study showed how to produce materials with great potential for insulation in the building area. This new class of recyclable composite material, less hydrophilic than the CNF aerogels, have good mechanical properties, thermal stability and thermal insulation properties.

Recycling polymeric waste from electronic and automotive sectors into value added products

The environmentally sustainable disposal and recycling of ever increasing volumes of electronic waste has become a global waste management issue. The addition of up to 25% polymeric waste PCBs (printed circuit boards) as fillers in polypropylene (PP) composites was partially successful: while the tensile modulus, flexural strength and flexural modulus of composites were enhanced, the tensile and impact strengths were found to decrease. As a lowering of impact strength can significantly limit the application of PP based composites, it is necessary to incorporate impact modifying polymers such as rubbery particles in the mix. We report on a novel investigation on the simultaneous utilization of electronic and automotive rubber waste as fillers in PP composites. These composites were prepared by using 25 wt.% polymeric PCB powder, up to 9% of ethylene propylene rubber (EPR), and PP: balance. The influence of EPR on the structural, thermal, mechanical and rheological properties of PP/PCB/ EPR composites was investigated. While the addition of EPR caused the nucleation of the β crystalline phase of PP, the onset temperature for thermal degradation was found to decrease by 8%. The tensile modulus and strength decreased by 16% and 19%, respectively; and the elongation at break increased by ~71%. The impact strength showed a maximum increase of ~18% at 7 wt.%–9 wt.% EPR content. Various rheological properties were found to be well within the range of processing limits. This novel eco-friendly approach could help utilize significant amounts of polymeric electronic and automotive waste for fabricating valuable polymer composites.

Flexural Properties of PVC/Bamboo Composites under Static and Dynamic-Thermal Conditions: Effects of Composition and Water Absorption

Polyvinyl chloride (PVC)/bamboo composites have been prepared and assessed for their use in interior and exterior load-bearing applications. PVC composites were formed by compounding PVC with different bamboo particle sizes and loadings. The mechanical properties of these composites were determined at both ambient and elevated temperatures and after long-term water soaking. Analysis revealed that bamboo incorporation improved the PVC composite flexural modulus which was also observed with dynamic mechanical-thermal analysis on heating composites toca.70°C. Addition of 25% and 50% bamboo particles increases flexural modulus by 80% with dependency on whether fine (<75 μm) or coarse (<1 mm) particles were used. On water soaking to saturation, composites had water weight uptakes of 10%, with reduced flexural properties obtained for all water-soaked composites. Nonetheless, the results of this study show that PVC/bamboo composites achieve the minimum flexural performance of ASTM D 6662, indicating potential for their use in exterior applications.

Influence of selective reinforcement in dynamic performance of glass-epoxy composites

Polymer composites are in the growing trend of replacing the metallic materials because of their ability toenhance the properties. Property enhancement in composites can be achieved by selective positioning of reinforcement in the matrix and it is termed as selective reinforcement. The reliability of a component in dynamic application depends on the effect of loading parameters. The flexural modulus of glass epoxy composite laminate exposed to dynamic loadingis experimentally investigated. This study isan experimental simulation for a leaf spring application. Two different unidirectional (UD)laminate configurations, 0/R/0/0/0 and 0/0/0/0 are fabricated with and without selective reinforcementby hand lay-up technique. The Taguchi’s DOE and L9 orthogonal array with two loading parameters (frequency and load cycle) are used to plan the experiments. The specimens are exposed to cyclic load using a disc camwith a rise of 6 mm at 2.6 Hz, 4.6 Hz and 8.6 Hz frequencies for 11X103, 22X103 and 33X103 cycles. The flexural modulus of the cyclic loaded laminates is measured by three point bent test (ASTM D 790). Experimental results are statistically analyzed by ANOVA, S/N ratio and Regression analysis. There exists a proportional raise in the flexural modulus of the cyclic loaded laminate and a shift in the effect of the loading parameters on composite flexural modulus attributed to selective reinforcement.

Recycling of waste artificial marble powder in HDPE‐wood composites

Waste artificial marble powder (AMP), an industrial waste generated from artificial marble processing, was recycled and incorporated in high‐density polyethylene (HDPE)‐wood composites. The results showed that waste AMP was mainly made up of aluminum hydroxide (Al(OH)3) and unsaturated polyester. Incorporating waste AMP into HDPE‐wood composites could increase the flexural strength and flexural modulus of composites but obviously decrease the notched impact strength. However, with the addition of maleic anhydride grafted polyethylene (MAPE), the mechanical properties of AMP/HDPE‐wood composites increased greatly. With 60 phr (parts per hundreds of resin) waste AMP, the notched impact strength and tensile strength of composites reached to 5.03 kJ/m2 and 28.0 MPa, respectively, increased by 98.1% and 55.6% compared to the composites without MAPE. Scanning electron microscopy (SEM) photographs revealed that MAPE improved the interfacial adhesion between fillers and HDPE matrix. In addition, the incorporation of waste AMP increased the heat resistance, limiting oxygen index (LOI) value of composites and decreased the horizontal burning rate. This study provides a new method for resource utilization of waste AMP, which could improve the performances of composites and avoid environmental pollution. POLYM. COMPOS., 39:2347–2355, 2018. © 2016 Society of Plastics Engineers

Mechanical and thermo-mechanical analysis based numerical simulation of granite powder filled polymer composites for wind turbine blade

In present article fabrication and characterization of unfilled and granite powder filled carbon epoxy composites are reported. Addition of carbon fiber shows positive effect on mechanical performance of the composites. However, incorporation of granite powder has negative hybridizing effect on the properties such as tensile strength, flexural strength and inter-laminar shear strength. The storage modulus evaluated at 30 °C is in close agreement with flexural modulus of composites. Further, successful attempt is made for numerical simulation of actual geometry of wind turbine blade. The results obtained from numerical analysis are comparable with experimental results.

Using maleic anhydride functionalized graphene oxide for improving the interfacial properties of carbon fiber/BMI composites

Maleic anhydride functionalized graphene oxide (MAH-GO) was synthesized and then introduced into carbon fiber (CF) reinforced bismaleimide (BMI) composites, with the aim of improving the interfacial adhesion strength between CF and BMI resin. Various characterization techniques including Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectra (XPS) and thermogravimetric analysis (TGA) demonstrated that the maleic anhydride has been suc- cessfully grafted onto the GO surfaces. The study showed that the interlaminar shear strength (ILSS) and flexural properties of CF/BMI composites were all improved by the incorporation of GO and MAH-GO, and the MAH-GO showed the sub- stantially improved effect due to the strong interaction between the MAH-GO and the resin matrix. The maximum increment of the ILSS, flexural strength and flexural modulus of composites were 24.4, 28.7 and 49.7%, respectively. Scanning electron microscope (SEM) photographs of the fracture surfaces revealed that the interfacial bonding between CF and resin matrix was significantly strengthened by the addition of MAH-GO. The results suggest that this feasible method may be an ideal substitute for the traditional method in the interfacial modification of composites.

Influence of selected submicron inorganic particles on mechanical and thermo-mechanical properties of unsaturated polyester/glass composites

In this paper, the influence of different submicron-scaled particles (zinc oxide, titanium dioxide, or silica) on mechanical and thermo-mechanical properties of unsaturated polyester matrix composites reinforced with glass fabric was investigated. Surface morphology of obtained composites was also examined. At first inorganic particles were mechanically dispersed into unsaturated polyester resin system as per the calculated weight ratio (2 or 4 wt% of polymer matrix). For prepared liquid dispersions viscosity was measured. Composites were produced by using hand lay-up method and contained 39–41 wt% of glass fibers. The flexural and dynamic mechanical analyses were carried out for each group of fabricated polyester/glass composites. All results were compared with the control samples (without submicron particles). It was found that addition of 2 wt% ZnO or TiO2 to unsaturated polyester resin enhanced the flexural strength and flexural modulus of composites. Dynamic mechanical analysis showed the increase of storage and loss modulus. Similar effect of submicron-scaled inorganic particles on Tg value of composites was observed. The scanning electron microscopic analysis of prepared composites showed good dispersion of submicron particles in polymer matrix and generally absence of voids was also observed.

Renewable Okra Bast Fiber Reinforced Phenol Formaldehyde Resin Composites: Mechanical and Thermal Studies

Okra bast fiber (OBF) reinforced thermoset phenol formaldehyde (PF) resin composites were prepared by compression molding methods. In order to found better wetting of filler and matrix, OBF was treated with NaOH. The properties of composites were studied by mechanical tests, thermal methods and water uptake. The mechanical properties such as tensile strength (TS), Young’s modulus (YM), tensile elongation, flexural strength (FS) and flexural modulus of composites were varied with NaOH concentration, treatment time and fiber loading. TS and FS were found to increase for fiber loading upto 30% and then decreased whereas YM, FM and tensile elongation were increased with increase of weight fraction. About 21% more TS and 85% more FS was found for 10% alkali treated fiber composite than untreated fiber composite. Treated fiber composites also showed greater thermal stability and lower water absorption property

The Study of Volume Electrical Resistivity and Mechanical Property of Double Continuous Phase PVDF/CBT Composite Containing Carbon Black and Graphite

The Poly(vinylidene fluoride)(PVDF)/Cyclic Butylene Terephthalate (CBT)/carbon black (CB)/graphite (GR) composites were prepared by melting blend method and were studied by milliohmmeter and material testing machine. The results showed that due to the formation of CB and GR conductive network, the volume electrical resistivity of PVDF/CBT/CB/GR composites linearly decreased as graphite content increased at below 4 wt% of graphite, but it in turn increased when graphite content was higher than 4 wt%. Flexural strength showed an increase at below 1.6 wt% of GR and gradually decreased as GR content increased further. Differently, flexural modulus of composites declined as GR content increased. In all composites, the flexural strength was more than 25 MPa, which satisfied with the requirements of bipolar plates.

Mechanical and thermal properties of polypropylene (PP) composites filled with modified shell waste

Shell waste, with its high content of calcium carbonate (CaCO3) plus organic matrix, has a potential to be used as a bio-filler. In this work, shell waste was modified by furfural and then incorporated to reinforce polypropylene (PP). The shell waste and modified powder were characterized by means of X-ray diffraction (XRD), scanning electron microscopy equipped with an energy dispersive spectrometer (SEM-EDS), X-ray photoelectronic spectroscopy (XPS), and Fourier transformed infrared spectroscopy (FTIR). The mechanical and thermal properties of neat PP and PP composites were investigated as well. Thermal gravimetric (TG) analyses confirmed the reinforcing role of modified powder in PP composites. The mechanical properties studied showed that adding modified powder could significantly increase the impact strength, elongation at break point and flexural modulus of composites. The maximum incorporation content could reach 15wt.% with a good balance between toughness and stiffness of PP composites. Differential scanning calorimetry (DSC) results showed that the modified powder could act as a nucleating agent and thus increase the crystallization temperature of PP. Polarized optical microscopy (POM) observation also indicated that the introduction of modified powder could promote the heterogeneous nucleation of PP matrix.

Mechanical Properties of Modified Natural Fiber/Poly(butylene succinate) Composites

More than one billion tons of banana leaves are discarded per year. Banana fibers can be made from banana leaves. In the present study, banana fibers without being processed (BF), banana fibers with an alkali treatment (BF-A), banana fibers treated in an alkali aqueous solution with tension (BF-AT), and poly(butylene succinate)(PBS) were used to make BF/PBS composites, BF-A/PBS and BF-AT/PBS composites by applying a twin screw extruder, respectively. The specimens were prepared using an injection molding machine. The three-point flexural test and the charpy impact test were conducted. The results of three-point flexural test showed that when the weight fraction of banana fibers was increased in composites, both flexural strength and flexural modulus increased. Flexural strength and flexural modulus of composites containing BF were higher than in composites containing BF-A. Flexural strength and flexural modulus of composites containing BF were higher than in composites containing BF-AT. The results of charpy impact test showed that when the weight fraction of banana fibers was increased in composites, impact strength increased. Charpy impact strength of composites containing BF-A was higher than that of composites containing BF. Charpy impact strength of composites containing BF-AT was higher than that of composites containing BF-A. The reason was verified that the surface treatment on banana fibers enhanced the polymer wettability and increased the broken-out displacement of composites.

Comparative study of aluminum diethylphosphinate and aluminum methylethylphosphinate‐filled epoxy flame‐retardant composites

AbstractEpoxy resin (EP) is one of the main polymers in electrical and electronic applications. In this work, flame‐retardant epoxy resin composites based on aluminum diethylphosphinate (Al(DEP)) and aluminum methylethylphosphinate (Al(MEP) were prepared using aromatic amine 4, 4‐diaminodiphenylmethane as curing agent. The flammability, thermal degradation, flexural properties, and morphologies of composites were investigated with respect to the filler loading and filler type. Results showed that both Al(MEP) and Al(DEP) were efficient flame retardants for EP and a low dosage (15 wt%) is enough to achieve the important criterion UL 94 V‐0. Limiting oxygen index (LOI) of composites is increased with filler loading (phosphorus content) and reached of 32.2% for 15 wt% of Al(MEP) and 29.8 for 15 wt% of Al(DEP). The char formation and flexural modulus of composites are also improved by adding the two fillers. However, the flexural strength of all the composites decreased with increasing filler loading. In comparison with Al(DEP)/EP, Al(MEP)/EP provides a higher flammability, better thermal stability and char formation but inferior flexural properties. Scanning electron microscopy revealed that the dispersion of Al(DEP) filler in the EP matrix is more uniform and exhibits better compatibility with EP matrix, which in turn generates better flexural strength and higher modulus when compared with Al(MEP)‐filled EP composites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers

Development of a new inexpensive green thermoplastic composite and evaluation of its physico-mechanical and wear properties

In the present study an attempt has been made to use turmeric spent (TS) as reinforcing filler to fabricate polypropylene (PP) green composite for load bearing and tribological applications. PP/TS composites were fabricated using varying amounts of TS viz, 10%, 20%, 30% and 40% (w/w) by twin screw extrusion method. The fabricated PP green composites were evaluated for physico-mechanical and tribological properties. Experimentally obtained tensile values were compared with theoretically predicted values using different theoretical models. Tensile modulus of composites increased from 1041 to 1771MPa with the increase in filler addition from 0 to 40wt.%. Flexural strength and flexural modulus of composites were improved after incorporation of TS into PP matrix. The water absorption characteristics of composites were determined. The effect of abrading distances viz., 150, 300, 450, and 600m and different loads of 23.54 and 33.54N at 200rpm on the abrasive wear behaviour were studied using dry sand/rubber wheel abrasive test rig. The TS filler lowered the abrasion resistance of PP/TS composites. The wear volume loss and specific wear rate as a function of abrading distance and load were determined. The surface morphology of tensile fractured green composites and their worn surface features were examined under scanning electron microscope.

Physical properties of current dental nanohybrid and nanofill light-cured resin composites

Objectives The purpose of this work was the detailed study of sorption characteristics of water or artificial saliva, the determination of flexural strength and the flexural modulus, and the study of the thermal stability of some current commercial dental light-cured nanocomposites containing nano-sized filler particles. Methods Three nanohydrid dental composites (Tetric EvoCeram (TEC), Grandio (GR) and Protofill-nano (PR)) and two nanofill composites (Filtek Supreme Body (FSB) and the Filtek Supreme Translucent (FST)) were used in this work. The volumetric shrinkage due to polymerization was first determined. Also the sorption, solubility and volumetric increase were measured after storage of composites in water or artificial saliva for 30 days. The flexural strength and flexural modulus were measured using a three-point bending set-up according to the ISO-4049 specification, after immersion of samples in water or artificial saliva for 1 day or 30 days. Thermal analysis technique TGA method was used to investigate the thermal stability of composites. Results GR and TEC composites showed statistically no difference in volumetric shrinkage (%) which is lower than the other composites, which follow the order PR < FSB < FST. The amount of sorbed water and solubility is not statistically different than those in artificial saliva. In all the composites studied the amount of water, which is sorbed (% on composite) is not statistically different than the amount of water, which is desorbed and follows the order: GR < TEC < PR < FSB < FST. After immersion in water for 1 day the highest flexural strength showed the FSB and the lowest TEC. GR, PR and FST showed no statistically different flexural strength. The flexural modulus of composites after immersion for one day follows the order TEC < PR≤FST < FSB < GR. Significance Among the composites studied, Grandio had the lowest polymer matrix content, consisting mainly of Bis-GMA. It showed the lowest polymerization shrinkage and water sorption and the highest flexural strength and flexural modulus after immersion in water or artificial saliva for 30 days. The water and artificial saliva generally showed the same effect on physical properties of the studied composites. Thermogravimetric analysis gave good information about the structure and the amount of organic polymer matrix of composites.