Increment In Tensile Strength Research Articles

Preparation and characterization of starch-based biocomposite films reinforced by Dioscorea hispida fibers

In this paper, Dioscorea hispida starch (DHS) biocomposites films were successfully prepared via combining D. hispida starch with sorbitol at different sizes (F1, F2) and concentrations (3, 6, and 9 wt%) D. hispida fiber (DHF) using a film-forming casting technique. Characterization via physical, morphological, mechanical, thermal, and biodegradability was conducted on the films. A significant increment in tensile strength (TS) of the D. hispida starch based films was found with rising fiber content 3–6% and a 9% decrement in concentration. The different sizes and concentrations of D. hispida fiber which were used with 6% small-sized fibers displayed the highest capabilities of increasing the tensile strength and decreasing elongation at break and possessing high value of Young's modulus. The findings demonstrated that tensile strength and Young modulus of the biocomposite films were increased after reinforcement with D. hispida fibers, and the optimal biofiller content was 6%. The biocomposites film revealed a novel waste material, D. hispida fiber, that is eco-friendly and easy to process. It also generates new information on the interactions of different fiber sizes and their effect on the film abilities, which can aid in development of biodegradable materials.

Influence of surface modifications of Castor oil fibre on mechanical properties of fibre reinforced Epoxy composites

ABSTRACT Castor oil fibre was identified as a new reinforcement for polymer-based composites and can be used in automobile applications. However, the mechanical properties of natural fibres were considerably less when compared with synthetic fibres and can be improved by the surface modification techniques via chemical treatment. In the present work, unidirectional castor oil fibre-reinforced epoxy composites were prepared by hand lay-up process. The tensile, flexural and impact strength properties of composites at 40% volume fractions were tested as per ASTM standards. Mercerised (NaOH) castor-oil fibre-reinforced composite exhibited 28%, 39%, 34%, 25%, 115% of the increment in tensile strength, tensile modulus, flexural strength, flexural modulus, impact strength respectively over untreated composites, the permanganate (KMnO4)-treated castor oil fibre-reinforced composites showed 9%, 35%, 15%, 15%, 85%, respectively. Thus, NaOH chemical treatment gives better results than KMnO4 chemical treatments due to the removal of unwanted material from surface effectively in NaOH treatments. The SEM results showed that the treated composites have a strong interfacial bond regarding untreated composites. Mechanical properties of the composites were predicted by using regression, ANN-single hidden layer, ANN-multi hidden layer models and confirmatory test results shows the reliability of predicted models. The ANN-multi hidden layer model giving the better results.

Mechanical and Thermal Properties of Epoxy/Poly(Styrene‐co‐Acrylonitrile) (SAN)/Organoclay Nanocomposites

AbstractThis article focuses on the investigations on mechanical and thermal properties of the epoxy/poly(styrene‐co‐acrylonitrile) (SAN)/cloisite 20A nanocomposites. The analysis is performed in two particular compositions of epoxy/SAN blends to study the effect of nanoclay addition. The compositions of blends, epoxy/5 phr SAN and epoxy/15 phr SAN, are selected based on the difference in phase separation mechanism and microstructure. An increment in tensile strength is observed for epoxy/5 phr SAN/1 wt% cloisite 20A nanocomposite. Young's modulus is increased in epoxy/15 phr SAN/cloisite 20A nanocomposites. A surge in the toughness and impact properties is observed for the nanocomposites. Beneficial increment in activation energy for thermal degradation is observed for epoxy/SAN blends and epoxy/SAN/cloisite 20A nanocomposites. The nanocomposites are suitable for high temperature applications without much compromise in the mechanical properties.

Additive manufacturing of high strength near β titanium alloy Ti-55511 by engineering nanoscale secondary α laths via in-situ heat treatment

In addition to the great merits of producing three-dimensional complex components from metallic powders in additive manufactured parts, the microstructural features can be tailored by the intrinsic heat treatment (IHT), i.e., cyclic re-heating without any additional post-treatment of the printed samples. Here we report that the microstructural configurations can be widely manipulated in an additive manufactured Ti-5Al-5Mo-5V-1Cr-1Fe (Ti-55511) near β titanium alloy, with an emphasis on the effect of IHT on the in-situ precipitation of α phase. The typical as-printed samples consist of prior-β grains, coarse primary α (α I ) colony and nanoscale secondary α (α II ) laths. Based on automatic quantitative image analysis, the increase of substrate temperature has a remarkable impact on accelerating the precipitation of nanoscale α II laths, while suppressing the precipitation kinetics of the primary α colony, and the corresponding volume fraction of α II laths increases from only 2% to more than 40%, resulting in a tensile strength increment from 900 MPa to 1200 MPa. The enhanced strength derives from those extremely fine α II laths in terms of boundary strengthening. The findings in this work provide a strategy of strengthening additively manufactured components by taking advantage of one step intrinsic heat treatment.

Performance Evaluation of Cellulose Nanofiber with Residual Hemicellulose as a Nanofiller in Polypropylene-Based Nanocomposite.

Residual hemicellulose could enhance cellulose nanofiber (CNF) processing as it impedes the agglomeration of the nanocellulose fibrils and contributes to complete nanofibrillation within a shorter period of time. Its effect on CNF performance as a reinforcement material is unclear, and hence this study seeks to evaluate the performance of CNF in the presence of amorphous hemicellulose as a reinforcement material in a polypropylene (PP) nanocomposite. Two types of CNF were prepared: SHS-CNF, which contained about 11% hemicellulose, and KOH-CNF, with complete hemicellulose removal. Mechanical properties of the PP/SHS-CNF and PP/KOH-CNF showed an almost similar increment in tensile strength (31% and 32%) and flexural strength (28% and 29%) when 3 wt.% of CNF was incorporated in PP, indicating that hemicellulose in SHS-CNF did not affect the mechanical properties of the PP nanocomposite. The crystallinity of both PP/SHS-CNF and PP/KOH-CNF nanocomposites showed an almost similar value at 55–56%. A slight decrement in thermal stability was seen, whereby the decomposition temperature at 10% weight loss (Td10%) of PP/SHS-CNF was 6 °C lower at 381 °C compared to 387 °C for PP/KOH-CNF, which can be explained by the degradation of thermally unstable hemicellulose. The results from this study showed that the presence of some portion of hemicellulose in CNF did not affect the CNF properties, suggesting that complete hemicellulose removal may not be necessary for the preparation of CNF to be used as a reinforcement material in nanocomposites. This will lead to less harsh pretreatment for CNF preparation and, hence, a more sustainable nanocomposite can be produced.

Combined effect of cassava starch nanoparticles and protein isolate in properties of starch‐based nanocomposite films

AbstractThis study aimed to evaluate the effects of incorporation of cowpea protein isolate and cassava starch nanoparticles obtained by ultrasound on the properties of cassava starch:glycerol films. The cowpea bean protein isolate was successfully obtained with 72.5% of protein and solubility about 90%. The cassava starch nanoparticles yielded 97.85%. Increasing protein isolate concentration in starch:glycerol films resulted in a progressive reduction of water vapor permeability up to 27.0%. The cassava starch nanoparticles added films presented expressive increments in tensile strength (283.83%) as well as modulus of elasticity (204.31%), accompanied by decreasing in elongation at break (24.28%). The thermal stabilities of cassava starch films were affected by the addition of both protein isolate and cassava starch nanoparticles. The cassava starch nanoparticles obtained by ultrasound ensured the maintenance of film properties, optimizing the production time, with a higher yield, and without the need for chemical reagents. Thus, it could be useful for substitution of those obtained by acid hydrolysis. Therefore, giving rise to a trend of production of nanocomposite films suitable for reinforced packaging applications.

Rotational Molding of Poly(Lactic Acid)/Polyethylene Blends: Effects of the Mixing Strategy on the Physical and Mechanical Properties.

In this study, blends of poly(lactic acid) (PLA)/linear medium density polyethylene (LMDPE) at different weight ratios were prepared by rotational molding. Two mixing strategies were used to evaluate the effect of phase dispersion on the physical and mechanical properties: (i) Dry-blending (DB) using a high shear mixer, and (ii) melt-blending (MB) using a twin-screw extruder. Thermal, morphological, and mechanical analyses were performed on the neat polymers and their blends. The thermal analysis was completed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), and the blends prepared by MB had lower thermal stability than the ones prepared via DB due to some thermo-oxidative degradation through the double thermal process (extrusion and rotomolding). The morphology of the rotomolded parts showed that DB generated larger particle sizes (around 500 µm) compared to MB (around 5 µm) due to the shear and elongational stresses applied during extrusion. The tensile and flexural properties of the rotomolded parts combined the PLA stiffness with the LMDPE toughness independent of the blending technique. Neat PLA presented increments in tensile strength (54%) and flexural strength (111%) for DB compared with MB. A synergistic effect in impact strength was observed in blends with 12 and 25 wt. % of PLA prepared by DB.

Influence of cellulosic and non-cellulosic particle fillers on mechanical, dynamic mechanical, and thermogravimetric properties of waste cotton fibre reinforced green composites

The textile waste fibre reinforced composites are sustainable in terms of their environmental and economic benefits. However, these composites have not attracted the attention of composite manufacturers. This research report waste cotton composites loaded with reduced graphene oxide (rGO) nanoparticles and enzyme-treated hemp fibre (HF) microparticles as a filler to improve their mechanical properties. The cotton/epoxy composite loaded with 0.3 wt% of rGO shows a ~11% increment in tensile strength, ~20% increment in flexural strength, and ~30% increment in impact strength. The cotton/epoxy composite loaded with 3 wt% of HF particles show enhancement in tensile, flexural, and impact strength by ~20%, ~14%, and ~116%, respectively. All the composites are thermally stable enough. The developed composites are potential materials for interior furniture of trains and buses.

Synergistic effect of crosslinking and dual reinforcement on the thermal and mechanical properties of polyvinyl alcohol

AbstractWe examined the combined effect of crosslinking and dual reinforcement on the thermal and mechanical properties of polyvinyl alcohol (PVA). Glutaric acid (GA) was used as crosslinker while tungsten disulfide nanotubes (WSNT) and carboxylated multiwall carbon nanotubes (f‐MWCNT) were used as dual reinforcing agents. Tensile strength and toughness of the hybrid composite, that is, crosslinked PVA reinforced with both f‐MWCNT and WSNT, was higher than those of neat PVA, crosslinked PVA, crosslinked PVA reinforced with WSNT and crosslinked PVA reinforced with f‐MWCNT. The hybrid composite showed remarkable improvement over neat PVA: tensile strength increased by 138%, Young's modulus increased by 142%, and toughness increased by 246%. Water uptake tendency and thermal stability of the composites were also examined and compared. The advantage of using dual reinforcement was a simultaneous increment in tensile strength and toughness, similar to what is observed in some natural materials like nacre.

Controlled Methodology for Development of a Polydimethylsiloxane-Polytetrafluoroethylene-Based Composite for Enhanced Chemical Resistance: A Structure-Property Relationship Study.

Polydimethylsiloxane (PDMS) polymers are highly appreciated materials that are broadly applied in several industries, from baby bottle nipples to rockets. Momentive researchers are continuously working to understand and expand the scope of PDMS-based materials. Fluorofunctional PDMS has helped the world to apply in specialty applications. Efforts are taken to develop such siloxane–fluoropolymer composite materials with good thermal, solvent, and chemical resistance performances. We leveraged inherently flexible PDMS as the model matrix, whereas polytetrafluoroethylene (PTFE) was used as the additive to impart the functional benefits, offering great value in comparison to the individual polymers. The composites were made at three different mixing temperatures, that is, 0–35 °C, and different loadings of PTFE, that is, 0.5–8% (w/w), were selected as the model condition. A strong dependency of the mixing temperature against the performance attributes of the developed composites was noted. Mechanical and thermal stability of the composites were evaluated along with optical properties. X-ray diffraction demonstrated the change in the crystallite size of the PTFE particles as a function of processing temperature. Compared to the phase II crystallite structure of the PTFE, the fibrils formed in phase IV imparted a better reinforcing capability toward the PDMS matrix. A synergistic balance between higher filler loading and mechanical properties of the composite can be achieved by doping the formulation with short-chain curable PDMS, with 238% increment of tensile strength at 8 wt % PTFE loading when compared to the control sample. The learning was extended to check the applicability of doping such PTFE powder in commercial liquid silicone rubber (LSR). In the window of study, the formulated LSR demonstrated improved mechanical properties with additional functional benefits like resistance toward engine oil and other chemical solvents.

Development and assessment of Moringa oleifera (Sahajana) leaves filler/epoxy composites: Characterization, barrier properties and in situ determination of activation energy

AbstractThis study concerns with investigation and analysis of hugely available, cost effective filler, obtained by grinding the Moringa oleifera leaves and its reinforcement in epoxy composites for semi‐structural applications. In this work, this novel filler is characterized by compositional analysis, FTIR, AFM, SEM, XRD, and TGA, along with the calculation of activation energy from two integral methods. To understand the interfacial surface chemistry of the fiber, X‐ray photoelectron spectroscopy (XPS) is also carried out. The size of filler was kept at 300 to 500 μm, and composites were prepared with five different loadings ranging from 5% to 25% using hand layup method of fabrication. The effect of varying loadings of filler on water uptake, mechanical, morphological, and thermal properties of its epoxy composites has been evaluated. Composites possess improved water resistance, tensile and flexural strengths in comparison with neat epoxy for an optimum loading of 20%, that is, 37 MPa. FWO and KAS methods are used to calculate the apparent activation energy of fillers. The apparent activation energy calculated from these methods comes to be 220 and 222 kJ/mol. The crystallinity index comes to be 55% which is comparable with other fibers. Approximately 12% increment in tensile strength and 10% in flexural strength takes place compared with neat epoxy at optimum fiber loading of 20%.

Exceptionally high strain-hardening and ductility due to transformation induced plasticity effect in Ti-rich high-entropy alloys

Ti-rich body-centered cubic (BCC, β) high-entropy alloys having compositions Ti35Zr27.5Hf27.5Nb5Ta5, Ti38Zr25Hf25Ta10Sn2, and Ti38Zr25Hf25Ta7Sn5 (in at%) were designed using bond order (Bo)-mean d-orbital energy level (Md) approach. Deformation mechanisms of these alloys were studied using tensile deformation. The alloys showed exceptionally high strain-hardening and ductility. For instance, the alloys showed at least twofold increment of tensile strength compared to the yield strength, due to strain-hardening. Post-deformation microstructural observations confirmed the transformation of β to hexagonal close packed (HCP, α′) martensite. Based on microstructural investigation, stress–strain behaviors were explained using transformation induced plasticity effect. Crystallographic analysis indicated transformation of β to α′ showed strong variant selection (1 1 0)β//(0 0 0 1)α′, and [1 − 1 1]β//[1 1 − 2 0]α′.

Influence of partial substitution of carbon black with silica on mechanical, thermal, and aging properties of super specialty elastomer based composites

AbstractThe reduction of the carbon black quantity in elastomeric composites is a massive requirement from environmental perspective and a huge challenge for industrial implementation. The present work consists of the replacement of half amount of carbon black with silica without compromising the basic properties along with ushering of superior characteristics of fluoroelastomer and silicone rubber blends. The comparative study of carbon black‐silica hybrid filler (1:1 ratio) with carbon black and silica at different loadings shows much superior aging behavior and thermal stability compared with the other composites with unforeseen increment of tensile strength (56%). The fundamentals of rubber‐filler interaction and reinforcement phenomenon of the hybrid filler composites have been determined by the correlation of the experimental findings with different models like Nicolais‐Narkis, Nielsen, Guth, and Kerner model. Furthermore, enhanced compatibility between the two rubber phases has been observed in terms of Tg shifting (3.8°C) and reduced FKM domain size (from 450 to 300 nm) in the silicone rubber matrix for hybrid filler composites. Morphological studies reflect the selected homogeneous dispersion of the carbon black in fluoroelastomer domain and silica in silicone rubber phase. These super specialty elastomeric composites can be used as oil and fuel resistant gaskets and O‐rings for wide temperature range.

Effect of quenching media on the properties of TiNi shape memory alloys fabricated by powder metallurgy

Abstract TiNi shape memory alloys (SMAs) are one of the significantly important materials group, which serve in the advanced applications requiring unique characteristics. Although their wide use is well established, further improvement of mechanical properties is still needed. The conventional TiNi SMA is usually manufactured by casting, hot forging and heat treatment processes. In this study, Ti-x at.%Ni alloys, with x equals 50, 51, and 52, were fabricated by powder metallurgy (PM) process through spark plasma sintering, followed by hot extrusion, homogenization, solution, aging and cryogenic quenching treatment. The effects of the compositions, processing conditions, and quenching media on the microstructural and mechanical properties of the alloys were evaluated by XRD, SEM, TEM analyses and tensile hysteresis test. The results showed that hot extrusion could lead to a considerable grain refinement, while the cryogenic quenching lead to a shift in the transformation temperatures and to an improvement of the tensile properties of the alloys such as the tensile strength increment and marginally improved ductility.

Effects of Benzoyl Treatment on NaOH Treated Sugar Palm Fiber: Tensile, Thermal, and Morphological Properties

In this study, the effects of benzoylation treatment on SPF were discussed. Five different parameters of SPF were compared, which were untreated, NaOH-pretreated, and benzoyl-treated SPF at 10, 15, and 20minutes soaking time. The physical properties showed that chemical treatment had caused decolouration of SPF, which 20minutes soaking time showed the brightest brownish colour, while the untreated had the darkest black colour. Significant reduction in diameter was found on benzoyl-treated at 15minutes compared to untreated SPF at 344.35μm and 480.33μm respectively. The diameter reduction was supported by images from scanning electron microscopy (SEM), which impurities were observed on the surface of untreated SPF compared to rough surface of benzoyl-treated SPF. Significant increment in tensile strength was found for all treated SPF compared to untreated SPF with the highest tensile strength of 173.99MPa showed by benzoyl-treated SPF in 15minutes. Analysis on the thermal properties showed that all treated SPF had lower degradation temperature due to the removal of impurities and moisture during chemical treatment. In general, different soaking time did not affect significantly on the thermal properties of fibres. The change in elemental groups of SPF was not observed before and after the treatment disregards different soaking time for benzoylation treatment. Pertaining the analyses conducted on all the properties of SPF in the current study, it can be suggested that 15minutes soaking time for benzoylation treatment exhibited the best properties of SPF to be used as reinforcement in composites.

Stability enhancement of highly loaded nano-clay-based flexible polyurethane foams using hollow glass microspheres

Addition of fillers in polyurethane foams enhances the mechanical properties of polymeric foams. However, fillers can be loaded to a certain extent, as higher percentage of fillers in polymeric foam causes structural instability leading to the collapse of foam. In this article, we report the use of hollow glass microspheres as a possible co-filler which enables higher loading of nano-clay in flexible polyurethane foam. It has been observed that the structural and mechanical properties of nano-clay-loaded foams were found to cause instability at 5 wt% loading of nano-clay. Therefore, upon addition of hollow glass microspheres in 5 wt%, nano-clay-loaded polyurethane foam shows remarkable enhancement in terms of stability and mechanical properties of the resultant foams. A 100-fold increment in tensile strength has been observed for 2 wt% hollow glass microspheres and 5 wt% nano-clay-loaded flexible polyurethane foams as compared to conventional (unloaded) polyurethane foams.

Fullerene-induced crystallization toward improved mechanical properties of solvent casting polycarbonate films

This work provides a facile strategy to induce crystallization of polycarbonate (PC) through solvent casting method. Pristine fullerene (C60) and PC-modified C60 nanoparticles are applied as nucleating agents for PC, and the crystallization behavior of PC nanocomposite films is controlled by solvent casting preparation conditions. To investigate the relationship between crystallization behavior and mechanical properties of PC nanocomposite films, X-ray diffraction, differential scanning calorimetry, polarizing microscope and tensile tests are carried out. Pristine C60 can only induce the formation of bulk PC spherocrystals which have no help or even deteriorates the mechanical properties of PC/C60 nanocomposite films. By contrast, the PC-modified C60 achieves uniformly disperse in the matrix and induces the formation of microcrystalline structures. It is found that appropriate degree of crystallinity for the PC/modified C60 nanocomposite films can effectively improve the mechanical properties. Typically, the PC/0.50 wt%-modified C60 nanocomposite films prepared under 40 °C by tetrahydrofuran exhibits up to a 33% increment in tensile strength and 45% increment in Young’s modulus compared to neat PC films.

Influence of printing parameters on structures, mechanical properties and surface characterization of aluminium alloy manufactured using selective laser melting

The selective laser melting (SLM) technology, a 3D printing method, has been gaining more attraction recently due to its ability to fabricate highly complex and intricate featured medical, aerospace, automotive components. The extensive use of SLM in recent years has been augmented by readily available processing materials and distinct product features such as enhanced surface properties and improved mechanical strength of the printed products. This paper investigated the effects of support structures, building direction and post-processing on mechanical properties, surface roughness and microscopic analysis of parts printed by SLM. Support structures are required during the SLM printing process. It is desired to optimize the support structures, as this increases printing time and material consumption and reduces surface finish. Finite element analysis has been carried out prior to metal printing to optimize the support structure. It was found that the spider-cone line support shows efficient structure for this study. The mechanical properties of the fabricated specimen were studied, and experimental results were validated and compared with conventionally machined specimen. It was observed that the SLM printed parts have 20% increment in tensile strength as compared with conventionally cast specimen. However, the percent of elongation is low for SLM specimen due to large number of pores and un-melted powder presented in the printed part. In this study, the SLM specimens were subjected to heat treatment at the temperature of 550 °C for 2 h in order to achieve increment or optimal mechanical properties. The heat treatment demonstrated a 2-fold increment in elongation, as compared with the SLM as printed specimen. The present study is also aimed at evaluating the surface roughness of SLM printed specimen. It was observed that the surface roughness of SLM specimen ranged between ~ 0.3 and 3 μm. This demonstrated that SLM process is capable of providing the good surface quality component and considered an alternative process to conventional manufacturing process. The morphological studies have been carried out to support the results derived from the evaluation of mechanical properties and surface roughness. The morphological behaviour clearly shows the large pores and un-melted particles in fractured specimen. The results revealed that the support structure, build direction, orientation, surface finish and post-processing are important parameters to build a part using SLM effectively and efficiently.

Lightweight, flexible MXene/polymer film with simultaneously excellent mechanical property and high-performance electromagnetic interference shielding

How to obtain high strength while remain the good shielding performance of MXene film is a big challenge, which limits its further application. Herein, we report on fabrication of mechanically strong and high-performance EMI shielding Ti3C2Tx composite film by incorporating of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) and then treatment with concentrated sulfuric acid to remove the insulating PSS. By introducing of 30 wt% PEDOT:PSS into Ti3C2Tx film and with acid post-treatment, the EMI SE of composite film with thickness of ~6.6 μm is up to 40.5 dB while the tensile strength is 38.5 ± 2.9 MPa and the increment in tensile strength is as high as 155% when compared to that of Ti3C2Tx film. It achieves a good balance between shielding performance and mechanical property, which has not been achieved in reported literatures. The combination of mechanical and shielding performances portfolio outperforms the counterpart of other polymer composites filled with MXene.

Enhancement of mechanical properties of glass fiber reinforced vinyl ester composites by embedding multi-walled carbon nanotubes through solution processing technique

This experimental study emphasizes the effect of the incorporation of multi-walled carbon nanotubes (MWCNTs) in conventional fiber reinforced-polymer composites on mechanical and thermal performance. Hand layup method was adopted for fabricating glass fiber reinforced vinyl ester (GVE), and 0.1 wt% MWCNTs filled GVE (MWCNT-GVE) composites. Bidirectional woven glass fiber (GF) and vinyl ester (VE) resin were used as reinforcement and matrix, respectively. The MWCNTs-VE suspension was prepared by solution processing technique. Mechanical properties were found to be affected by embedding MWCNTs in the neat GVE composite. MWCNT-GVE composite showed about a 7.37% increment in flexural strength and about 11.64% increment in tensile strength over neat GVE composite. Through differential scanning calorimetry (DSC), glass transition temperature (Tg), and the effect of MWCNTs on thermal properties of experimental composites were analyzed. A decrease in Tg value was observed after incorporating MWCNTs in GVE composite. Post failure, analysis was done by scanning electron microscope (SEM).