Bending Strength Of Composites Research Articles

Effects of aligned carbon nanotube microcolumns on mechanical and thermal properties of C/SiC composites prepared by LA-CVI methods

Herein, C/SiC-CNTs composites were prepared by laser assisted chemical vapor infiltration (LA-CVI) method combined with vacuum impregnation. Density, mechanical property and thermal conductivity of as-prepared composites were then investigated by various analytical methods. Scanning electron microscopy (SEM) revealed good dispersion of CNTs in C/SiC-CNTs between composites layers and directional heat transfer channels. This formed unique three-dimensional connected networks, reinforcing multi-scale composites matrix. Average density and bending strength of composites were estimated to 2.35 g cm−3 and 598 MPa, respectively, which is 20.5% and 27.2% higher than those of CVI-C/SiC composites. The comparison between theoretical thermal conductivity and experiments revealed that the overall thermal conductivity of LA-CVI-C/SiC-CNTs composites (150.42 W m−1 K−1) was nearly 25 times higher than that of CVI-C/SiC composites.

Thermodynamic Study on Self-propagating High Temperature Synthesis of TiB2/Fe Composites

Based on the experimental analysis and theoretical calculation, the self-propagating high temperature synthesis of TiB2/Fe composite was studied. The experimental results show that the interfacial between TiB2 and Fe was smooth and clear, and the composite bending strength increased with the addition of Fe, however, the hardness decreased accordingly. The thermodynamics of the composites preparation process was calculated. The calculation results show that the primary chemical reaction was the reaction between Ti and B. The extra B can react with Fe, producing the brittle phase Fe2B. By increasing Ti, the production of Fe2B will decrease and a few of Ti-Fe intermetallic compound will be produced by the reaction between Ti and Fe in the composites. Finally, according to the Merzhanov condition of the adiabatic system, it is concluded that the Fe content must be selected between 16.3% and 54.3% by the thermodynamics temperature of reaction calculation.

Sintering temperature dependent micro and macro mechanical properties of Si3N4f/SiO2 composite materials

Wave-transparent materials for the high temperature use require highly reliable mechanical properties and excellent anti-oxidation performance. This study reports the densification, interfacial evolution, micro and macro mechanical properties of Si3N4f/SiO2 composites sintered at 800–1200 °C. The results show that significant shrinkage of silica matrix at 1100–1200 °C helps improve the density of Si3N4f/SiO2 composites, but also leads to an obvious reduction of mechanical properties. The bending strength of composites sintered at 800–1000 °C reaches 166.5–174.0 MPa, but linearly decreases to 102.5 MPa at 1100 °C and 19.8 MPa at 1200 °C. Similarly, fracture toughness also experiences a linear decline, decreasing from 7.0 to 7.2 MPa m1/2 at 800–1000 °C to around 3.7 MPa m1/2 at 1100 °C and 1.0 MPa m1/2 at 1200 °C. As to the high-temperature performance, the in-situ bending strength at 1200 °C of the 800–1000 °C sintered composites is lower than 75Mpa. Interfacial diffusion cooperated with the uneven shrinkage of silica matrix is regarded as major reasons to the degradation of composites sintered or tested at over 1100 °C, for that they can lead to an increase of fiber-matrix interfacial bonding and trigger the generation of internal stresses and even visible cracks.

PENGARUH VARIASI JUMLAH LAPISAN FIBERGLASS DAN ANYAMAN BAMBU TERHADAP KEKUATAN BENDING KOMPOSIT DENGAN METODE VACUUM ASSISTED RESIN INFUSSION (VARI)

The objective of this research is to obtain the bending properties of composite material produced by VARI method, and to get analysis of polyester resin distribution time on the layer of fiberglass composite and bamboo woven strip.The process of making composites varies, but the process of making this research is the process of Vacuum Assisted Resin Infusion (VARI). In the VARI process, dry fiber is placed between the fixmold and plactic bag, then the resin is injected after the chamber inside the low- pressure plastic bag and the process continues until all parts of the fiber are wetted by the resin.From the results of research, testing and discussion of bending test results that have been done then can be drawn conclusions include: Variation of the number of reinforcement layer on VARI method will affect the value of bending strength of composite. By using the VARI method The highest average value of bending stress occurs in variation 4 (206,69 MPa), while the lowest occurs in variation 1 (42,83 MPa), and the time required for the distribution of resin varies in time variation 1 which takes 5 minutes 02 seconds, while for variation 4 takes 8 minutes 3 seconds.Keywords: composites, VARI method, glass fiber, bending test

Estimation of Strength of Composites Reinforced with Woven Preform

Bending strength of composites produced by using two layers of woven preforms from glass and flax rovings is studied experimentally. Statistically significant models describing the process of deformation of the studied composite samples are constructed. A method of nondestructive monitoring is proposed for estimating strength of two-layer composites produced by using two-layer woven preforms.

Effect of polyethylene glycol on mechanical properties of bamboo fiber‐reinforced polylactic acid composites

ABSTRACTThe bamboo fiber (BF)‐reinforced polylactic acid (PLA) composites were prepared using the twin‐screw extruder and injection molding. Thermal gravimetric analyzer results indicated the thermal stability of BF/PLA composites decreased with increasing BF content. Differential scanning calorimeter and X‐ray diffraction curves showed that BF played a role as a nucleating agent, but the crystallinity of composite materials decreased with the increasing BF content. The melt flow rate of composites reduced with the increase in BF content, resulting in a poorer processing property. The processability of the composites was improved with the addition of high molecular polyethylene glycol (PEG). Mechanics performance test showed that tensile strength and bending strength of composites increased at low loading with the BF content increased then decreased when the loading continued to increase. The tensile strength of the composite materials reached 65.46 MPa when alkali‐treated BF (ABF) content was 20 wt %. The flexural strength of the composites reached 97.94 MPa when ABF content was 10 wt %. Impact performance has also been improved. PEG‐20000 was the best plasticizer among the PEG‐6000，PEG‐10000, and PEG‐20000. When the component of PEG was 10 wt %, the elongation increased by 56%. The scanning electron microscopy (SEM) result showed that the fracture of the composites was smooth, most ABF were wrapped in matrix and distribution of ABF in PLA matrix was more uniform. It means that interfacial compatibility of bamboo fiber and PLA improved after BF modified by alkali. High molecular weight PEG enhance melt flow ability of polymer, result in fibers were further enclosed in the PLA matrix and increase properties of composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47709.

Polyester Composite Bending Strength Optimization Strengthened with Coastal Cottonwood Tree Bark Fiber and Fly Ash Filler

Composite material is a combination of more than one type of material and is designed to get the best combination of characteristics from each constituent component. Composite materials have many advantages, including lighter weight, higher strength and durability, corrosion resistance and wear resistance. This study aims to determine the optimum conditions of polyester composites bending strength reinforced with Coastal Cottonwood bark fibers and fly ash fillers. The method used was alkalizing the fiber of coastal cottonwood tree bark by immersing 5% NaOH solution for 2 hours. The specimen was made by the Hand Lay-Up method, the fiber volume fraction was 35.8; 40; 50; 60 and 64.14% with filler 2,93; 5; 10; 15 and 17.071%. Bending testing used the ASTM D790 standard and data analysis used the response surface method with Central Composite Design. The optimization results showed the best conditions were in the fiber volume fraction of 52.79% and filler volume fraction of 9.73% with a bending strength of 101.05 N/mm2. The mathematical model obtained from the experiment is: y = 100.296 + 5.009 x1 – 2.710 x2 – 10.285 x12 - 3,006 x22 - 1,415 x1*x2. Surface response method is an efficient method used to determine the levels of free change that can optimize response.

Effect of pressure-free heating curing time on bending property of 2D T700/E44 composites prepared by ICM

Six kinds of 2D T700/E44 composites with pressure-free curing times of 40 min, 60 min, 80 min, 100 min, 120 min and 140 min are prepared by improved compression molding process (ICM). The macroscopic morphology of the composites is satisfactory. The microstructure observation and bending performance tests show that composites have poor infiltration effect. When the pressure-free curing time is less than 80 min, defects are easy to occur such as insufficient infiltration and voids. Bad infiltration and void defects will lead to poor continuity of carbon fiber and resin, and their bending fracture will also be unreasonable, so the bending strength of composite at 40 min is 275 MPa. The infiltration effect is gradually improved with the increase of pressure-free heating curing time. However, when the pressure-free heating curing time reaches 120 min or more, the infiltration effect of the composites is deteriorated, and this is due to excessive infiltration time and extrusion force in subsequent heating extrusion infiltration process. Defects such as fiber aggregation and uneven infiltration are prone to occur, and bending strength of composites reduces to 380 MPa. When the pressure-free curing time is 100 min, the infiltration effect of the prepared composite is satisfactory, and the imbalanced infiltration and hole defects are effectively eliminated. The bending fracture of composite material is uneven, carbon fibers and resin play the roles of reinforcement and transferring loads effectively respectively, so the bending strength of the prepared 2D T700/E44 composite reaches 730 MPa.

Microstructure and Mechanical Properties of AlN Particle Reinforced Mg-Al Matrix Composites with Different Particle Contents

In this paper, magnesium matrix composite with different AlN particles content were fabricated by powder metallurgy. The microstructure of composites was investigated by scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS) and transmission electron microscopy (TEM). The mechanical properties of composites were measured by electronic universal testing machine. The results show that the best densification and the highest mechanical properties of composites reached when the addition of 6wt.% reinforcement at 620 °C for 1 hour. Additionally, the compressive strength and bending strength of composites were 217.06 MPa and 207.40 MPa respectively, increased by 79.2% and 91.12% compared with matrix alloy, and the reinforcement particles uniformly distributed in the matrix alloy. It may be concluded that the strengthening mechanism of composites is mainly attributed to grain refinement, load transfer, and dislocation strengthening.

Effects of oxygen plasma treatment power on Aramid fiber III/BMI composite humidity resistance properties

The effects of oxygen plasma treatment power on Aramid Fiber III chemical structure and its reinforced bismaleimides (BMI) composite humidity resistance properties were investigated in this work. The aramid fiber III chemical structure under different plasma treatment power were measured by FTIR. The composite bending strength and interlinear shear strength with different plasma treatment power before and after absorption water were tested respectively. The composite rupture morphology was observed by SEM. The FTIR results showed that oxygen plasma treatment do not change the fiber bulk chemical structure. The composite humidity resistance of bending strength and interlinear shear strength are similar for untreated and plasma treated samples. The retention rate of composite bending strength and interlinear shear strength are about 75% and 94%, respectively. The composite rupture mode turns to be the fiber failure after water absorption.

Wire electrical discharge machining of 3Y-TZP/Ta ceramic-metal composites

Dense (>98 th%) and homogeneous ceramic/metal composites were obtained by spark plasma sintering (SPS) using ZrO2 and lamellar metallic powder of tantalum (20 vol%) as starting materials. Composites showed a fracture toughness value of 16 MPa m1/2 mainly due to crack bridging of the elastic–plastic deformations of ductile metal particles. This fracture toughness was accompanied by a simultaneous enhancement in damage tolerance and fatigue resistance of 3Y-TZP/Ta composites.Besides exceptional mechanical properties, SPS sintered 3Y-TZP/Ta composites also showed the electrical conductivity suited to wire electrical discharge machining (WEDM). Therefore, they are suitable to be produced in mechanically performant, complex shape components with the required tolerance while reducing machining costs. The aim of this work was the study of the electrical properties of the materials as well as the characteristics of the machining process and the machined surfaces influence on the bending strength of composites. The results show that workpieces can be machined with high accuracy and without a drop in mechanical strength.

Surface treatment of ultra‐high molecular weight polyethylene fibers using potassium permanganate and mechanical properties of its composites

Potassium permanganate was applied to improve the surface properties of the ultra‐high molecular weight polyethylene (UHMWPE) fibers. The results suggested that the surface oxygen atoms increased dramatically and the O/C ratio increased from 0.030 to 0.563 after treatment. The increased surface roughness and the O‐containing groups on the treated fiber surface decreased the contact angles with water and ethylene glycol. The crystallinity and the crystallite size of the treated fibers increased, and the DSC results indicated that chain scission and the formation of ―C═O chemical defects in the amorphous region were the main mechanisms of the deterioration of the treated UHMEPE fibers. The breaking strength and the elongation at break of the fibers decreased, but the modulus increased after treatment. The treated fibers exhibited better adhesion with epoxy matrix. An improvement of 27.6% from 101.4 to 129.4 MPa in ILSS confirmed the improvement in the interfacial adhesion strength of composites. The impact and bending strength of composites were both improved.

Thermal Sensitive Shape Memory Behavior of Epoxy Composites Reinforced with Silicon Carbide Whiskers

A novel shape memory polymer composite was fabricated by introducing various amounts of silicon carbide whiskers (SiCws) into a shape memory epoxy. The relationship between the thermomechanical properties of the system and structural changes were investigated via dynamic mechanical analysis, scanning electron microscopy, and bending tests. The results show that the bend strength of composites can improve by 64.1% when SiCw content reaches 12 wt %. The shape transition temperatures of SiCw/epoxy composites decreased slightly with the increase in SiCw content, but it was noted that all of the composites showed excellent shape memory properties. The shape fixity ratio increased as SiCw content increased (>99%), and the shape recovery ratio slightly decreased as SiCw content increased (>95%). All of the composites nearly recovered to their original shape within 2 min (not 100%), and the shape recovery speed significantly improved at a higher temperature. It is anticipated that tagging products will be used in the aerospace industry.

Effects of dry method esterification of starch on the degradation characteristics of starch/polylactic acid composites

Maleic anhydride esterified corn starch was prepared by dry method. Esterified starch/polylactic acid (PLA) biodegradable composite was produced via melt extrusion method with blending maleic anhydride esterified corn starch and PLA. The influence of the dry method esterification of starch on the degradation characteristics of starch/PLA composites was investigated by the natural aging degradation which was soil burial method. Test results of mass loss rate showed that the first 30 days of degradation was mainly starch degradation, and the degradation rate of esterified starch/PLA (ES/PLA) was slower than that of native starch/PLA (NS/PLA). Therefore, the damage degree of ES/PLA on the surface and inside was smaller than that of NS/PLA, and the infrared absorption peak intensities of CO, CO and CH were stronger than that of NS/PLA. With the increasing time of soil burial degradation, the damage degree of NS/PLA and ES/PLA on the exterior and interior were gradually increased, whereas the infrared absorption peak intensities of CO, CO and CH were gradually decreased. The XRD diffraction peak intensity of PLA in composites showed an increased trend at first which was then followed by a decreased one along with the increasing time of soil burial degradation, indicating that the degradation of amorphous regions of PLA was earlier than its crystalline regions. When the soil burial time was the same, the diffraction peak intensity of PLA in ES/PLA was stronger than that of NS/PLA. If the degradation time was the same, T0, Ti and residual rate of thermal decomposition of NS/PLA were larger than those of ES/PLA. The tensile strength and bending strength of composites were decreased gradually with soil burial time increasing. Both the tensile strength and bending strength of ES/PLA were stronger than those of NS/PLA.

Bending mechanical property and failure mechanisms of woven carbon fiber-reinforced aluminum alloy composite

Copper-coated woven carbon fiber-reinforced aluminum alloy composite was prepared by spark plasma sintering (SPS). Microstructure, three-point bending mechanical property, and the failure mechanisms of the composite were investigated. Microstructure observation shows that the carbon fibers bond compactly with matrix alloy. Compared with the matrix aluminum alloy, the bending strength, ductility, fracture energy, and cracking resistance of the composite are evidently improved. Microstructure analyses reveal that the high specific strength of carbon fibers and transfer of stress from matrix alloy to carbon fibers are responsible for the increase of the composite bending strength. The expanding of cracks is restrained, and cracking resistance of the composite is improved by adding woven carbon fiber. Attributed to the carbon fibers’ debonding, cracks deflection, and multipath propagation mechanisms, the fracture energy of the composite increases.

Porous Bulk Specimens in CaO‐MgO‐SiO2 Systems Using Steel Slag and Altered Additives by Conventional Sintering

To obtain the porous, bulk, brick like samples the following mixtures were pressed and sintered at different temperatures: steel slag, sintering aids (soda lime glass, sodium phosphate), and common foaming additives (like dolomite, perlite). The bulk densities of final composites were from 1.3 to 2.41 g/cm3, and open porosities were from 15 to 40 vol%. The bending strengths of composites varied from 5.5 to 15.9 MPa. The final phase of sintered samples was forming of calcium magnesium silicate. The samples which had 80 wt% slag–5 wt% SiC–5 wt% perlite–5 wt% boric acid–5 wt% sodium phosphate showed the 40 vol% porosity and 6.7 ± 0.2 MPa bending strength.

Effect of Functionalization of Multi-Walled Carbon Nanotubes on the Electrical Conductivity and Mechanical Properties of Unsaturated Polyester Resin Composites

As the unsaturated polyester resin (UPR) has multiple functional groups, it can be solidified at ambient temperatures and pressures. But the low mechanical properties limit its application. In this paper, the functional multi-walled carbon nanotubes (MWCNTs) were modified by maleic anhydride to synthesize UPR composites by condensation reaction. Then we obtained the UPR composites with oriented MWCNTs by application of external electric field. The microstructure, electrical conductivity and mechanical properties of UPR composites were investigated by scanning electron microscope, infrared spectroscopy, impedance analyzer and universal testing machine. It was found that the composites are anisotropy and the tensile strength and bending strength of composites with 0.5 wt.% lengthways MWCNTs are improved by 70%, 43%, the compressive strength with 0.5 wt.% is improved by 90%, the electrical conductivity increased to 107 S/cm when the contents reach to 1%.

Effect of thermal cycling on the mechanical properties of Cf/Al composites

An unidirectional ultra-high modulus M40J carbon fiber reinforced 5A06 aluminum alloy with volume fraction of 55% was fabricated by the pressure infiltration method. The effect of thermal cycling (−70 to 120°C and −196 to 120°C) on the mechanical properties of Cf/Al composites was investigated. Bending modulus increased abruptly after five thermal cycles and then reached a platform. However, after 50 cycles, the bending modulus decreased with the increase of cycles due to generation and propagation of microcracks at C fiber/Al interface. The bending strength of composites showed fluctuations between 800 and 1000MPa, and the amount and length of pull-out fiber increased with the increase of the thermal cycling times regardless of temperature difference. Microstructure observation revealed the formation of microcracks and interface debonding at the C fiber/Al interface after thermal cycling treatment, and the amount of the microcracks and interface debonding increased with the temperature difference. The main interfacial products in annealed Cf/Al composites were rod-like Al3Mg2 and bulky Al58Mg42, and no significant Al4C3 was observed at C fiber/Al interface. The thermal cycling treatment used in the present work had little effect on the interface microstructure of Cf/Al composites. Very few dislocations were observed in the Al matrix of annealed Cf/Al composites. However, the amount of dislocations in the Al matrix increased gradually with the increase of thermal cycles. Moreover, the amount of dislocations would decrease after a certain thermal cycles due to movement and annihilation of unlike-sign dislocations.

Preparation and Characterization of Phosphorylated Collagen and Hydroxyapatite Composite as a Potential Bone Substitute

Abstract On the basis of the hypothesis that phosphate groups introduced on collagen can induce the mineralization in natural hard tissue, first, type I collagen (extracted from bovine tendon) was phosphorylated with sodium trimetaphosphate (STMP). The subsequent growth of hydroxyapatite (HAP) on the phosphorylated collagen nanofibers was achieved through a precipitation reaction. The FTIR results indicated that the phosphate groups were incorporated onto the collagen surface through treatment with STMP. During the mineralization process, the rod-like crystals converged into layers of a flaky structure formed on the surface of the phosphorylated collagen, while plate-like minerals were obtained on the pure collagen, as indicated by the SEM and XRD findings. The bending strength of composites isopressed at 180 MPa also displayed a significant increase. The test results demonstrated that phosphate groups had indeed been introduced into the collagen molecules and gave rise to the superior mechanical behavior of the composite materials.

Study Kekuatan Bending Dan Struktur Mikro Komposit Polyethylene Yang Diperkuat Oleh Hybrid Serat Sisal Dan Karung Goni

AbstractThe purpose of this study is to investigate and study the mechanical properties of polyethylene strukrur micro hybrid composites reinforced by fibers sisal and jute sacks.Preparation of composites by hand lay-up method with a ratio of fiber volume fraction of sisal and jute sacks 30%: 0%, 20%: 10%, 15%: 15%, 10%: 20%, 0%: 30%. With unidirectional sisal fiber orientation and fiber length random burlap gunny sack fibers 2 cm. Specimen testing is performed with a standard bending test ASTM D790, and microstructure.Test results obtained from the average bending strength of composites with high fiber volume ratio fraksin 30%: 0% is 74.43 Mpa. While the lowest average for bending strength found in composites with fiber volume fraction of 0%: 30%, the bending strength of 32.21 MPa. Therefore we can conclude the increasing volume fraction of sisal fiber with unidirectional fiber orientation, the higher the bending strength of its appeal and reverse the growing volume of burlap fibers with random orientation of the fibers feeding the lower the bending strength and the strength.