Influence of pineapple leaf fiber and it's surface treatment on molecular orientation in,and mechanical properties of,injection molded nylon composites

The objective of his work is to show that pineapple leaf fiber (PALF) can be used successfully to reinforce a high melting polymer such as nylon. One of the most important barriers to the utilization of lignocellulosic materials in polymer matrix composites is their limited temperature resistance. As a consequence, they are mostly used to reinforce low melting temperature polymers such as polyethylene and polypropylene as well as polystyrene. However, this work reveals that PALF can be used to reinforce nylon. This is because of its very low lignin content. Nylon 6/66 composites containing a fixed amount of 20 wt % PALF in the form of short and fine fibers were prepared with a laboratory twin screw extruder and then injection molded. The mechanical properties of three types of PALF, i.e. untreated, alkaline- and silane-treated, were studied. Significant improvements in modulus and heat distortion temperature were obtained. The crystalline structure and orientation in the injected composites were investigated with synchrotron wide angle x-ray scattering (WAXS). It was found that both PALF and nylon crystallites oriented well along the flow direction and this is the key factor for the improvements observed.     

A review on potential development of flame retardant kenaf fibers reinforced polymer composites

Kenaf fibers have been extensively explored from the past few decades in polymer composites industries owing to its extensive adaptations, excellent properties together with its comparable mechanical properties to traditional glass fibers polymer composites. The combustibility or lowered flame retardancy hampered the diverse applications of kenaf fibers reinforced polymer composites, as it affects the mechanical strength and stiffness of composites during fire. Current review article intended to be a comprehensive source of published literature involving the flame retardants (FRs), types and applications of FRs and the fabrication of kenaf fibers reinforced polymer composites. This article will also provide a perfect data on the recent development of the FR kenaf fibers polymer composites with different FRs and explored its structural and semi‐structural industrial application for performing further research in this topic. Copyright © 2016 John Wiley & Sons, Ltd.     

Mechanical properties and frictional resistance of Al composites reinforced with Ti_3C_2T_x MXene

Two-dimensional(2D) Ti_3C_2T_x MXene is an attractive additive not only used in base oil due to its low friction coefficient,but also used in composites due to its high aspect ratio and rich surface functional groups.So far there has been intense research into polymer matrix composites reinforced with Ti_3C_2T_x,Here we report on the use of 2D Ti_3C_2T_x to enhance the mechanical and frictional properties of Al matrix composites.Ti_3C_2T_x/Al composites were designed and prepared by pre s sureless sintering followed by hot extrusion technique.The prepared composites exhibit a homogeneous distribution of Ti_3C_2T_x.The Vickers hardness and the tensile strength continuously increase with increasing Ti_3C_2T_x content.A hardness of 0.52 GPa and a tensile strength of 148 MPa were achieved in the 3 wt% Ti_3C_2T_x/Al composite.The frictional properties of pure Al and the Ti_3C_2T_x/Al composite were comparably studied under dry sliding.A low friction coefficient of 0.2,twice lower than that of pure Al,was achieved in the 3 wt%Ti_3C_2T_x/Al composite.Ti_3C_2T_x acting as a solid lubricant reduces the abrasive wear in the composite,improving the frictional properties of Al matrix composites.     

Friction and wear properties of combined surface modified carbon fabric reinforced phenolic composites

Carbon fabric (CF) was surface treated with silane-coupling agent modification, HNO₃ oxidation, combined surface treatment, respectively. The friction and wear properties of the carbon fabric reinforced phenolic composites (CFP), sliding against GCr15 steel rings, were investigated on an M-2000 model ring-on-block test rig. Experimental results revealed that combined surface treatment largely reduced the friction and wear of the CFP composites. Scanning electron microscope (SEM) investigation of the worn surfaces of the CFP composites showed that combined surface modified CFP composite had the strongest interfacial adhesion and the smoothest worn surface under given load and sliding rate. SEM and X-ray photoelectron spectroscopy (XPS) study of carbon fiber surface showed that the fiber surface became rougher and the oxygen concentration increased greatly after combined surface treatment, which improved the adhesion between the fiber and the phenolic resin matrix and hence to improve the friction-reduction and anti-wear properties of the CFP composite.     

Property correlations for composites based on ethylene propylene diene rubber reinforced with flax fibers

EPDM composites filled with short flax fibers were prepared by melt blending procedure. The effects of fiber loading on the mechanical, thermal and water uptake characteristics were studied. The physico-mechanical, morphological thermal properties and water absorption behavior were discussed using tensile testing, differential scanning calorimetry, thermogravimetrical analysis and scanning electron microscopy. Scanning electron microscopy revealed that the flax fibers were well dispersed in the polymer matrix. The tensile strength and hardness of the composites were found to be improved at higher fiber loading. The water absorption pattern of EPDM/fiber composites at room temperature follows a Fickian behavior for composites with 10, 15 and 20 phr flax fiber.     

Extraction and refinement of agricultural plant fibers for composites manufacturing

Because of their excellent tensile properties, low density, and natural abundance, cellulose-based plant fibers are a sustainable and biodegradable alternative for synthetic fibers in fiber-reinforced composite materials. However, the extraction of plant fibers can be costly and difficult to control because the fibers are enmeshed in a complex network of biopolymers (principally lignin, pectin, and hemicellulose), which serve both to strengthen the fibers and to bind them to their parent organism. It is necessary to extract or degrade these biopolymers to produce fine plant fibers without adversely altering the fibers themselves in the process. In particular, it is important that both the molecular weight and the degree of crystallinity of the cellulose in the fibers be kept as high as possible. This article reviews chemical treatments, which have been used to extract and refine fibers both from purpose-grown fiber crops, such as hemp and flax, and agricultural waste such as coconut husks and pineapple leaves. The treatments are discussed in terms of changes in the mechanical properties and surface chemistry of the fibers.     

Preparation,characterization and properties of fiber reinforced composites using silicon‐containing hybrid polymers

A novel glass fiber reinforced composite was prepared by using silicon‐containing hybrid polymers, poly(methylhydrogen‐diethynylsilyene) (PMES) and poly(phenylethynyl‐silyloxide‐phenylborane) (APABS), as matrix resins. The curing behavior and rheological properties of the matrix resins were investigated by differential scanning calorimetry (DSC) and rotational rheometer. The dynamic viscoelastic properties, mechanical properties, and microstructures of the composites were studied by dynamic mechanical analysis (DMA), universal testing machine (UTM), and scanning electron microscopy (SEM), respectively. The results show that the composite can be well cured between 200 and 300 °C through reactive groups like Si‐H, N‐H, and C≡C units, the possible thermosetting mechanism is also proposed. The composites exhibit excellent mechanical properties with bending strength reach up to 261 and 178 MPa before and after heat‐treating, respectively. SEM analysis clearly indicates that crack in the matrix, matrix/fiber interface debonding, and fiber pull out are predominate failure mechanism for the composites which are heat‐treated in different temperatures. All these obtained results can give theoretical guiding reference for their further applications. Copyright © 2016 John Wiley & Sons, Ltd.     

Experimental investigation on the mechanical properties of Cyperus pangorei fibers and jute fiber-based natural fiber composites

The present era uses natural fibers as a partial replacement for synthetic fibers, thereby utilizing eco-friendly materials in a number of automotive applications (namely, bumpers, wind shields, doors, ceilings, etc.). Although there are many research findings related to natural fiber composites, in this work, a new sandwich layer of Cyperus pangorei fibers and jute fiber epoxy hybrid composites is developed using the hand lay-up technique and compared with the pure Cyperus pangorei fiber and pure jute fiber epoxy composites. The mechanical properties like tensile, flexural, compressive, impact, and hardness are performed as per ASTM standards for the developed composites. The test results show that Cyperus pangorei hybrid composite 3 had a tensile strength of 50.2 MPa, flexural strength of 301.48 N mm^?2, ultimate compression load of 15.03 KN, impact energy of 6.34 J, and Shore D hardness of 82.7, which are superior by 1.1–1.5 times to all the other developed composites. The microstructural characterizations are performed using scanning electron microscope which played a vital role in analyzing the failure morphology of the composites.     

A state-of-the-art review on particulate wood polymer composites: Processing,properties and applications

In the present decade, the demands for recyclable, environmentally friendly and low-cost with good strength composites materials have been significantly increased. In this context, the particulate wood polymer composites have attracted the researchers owing to their eco-friendliness, low-cost as they are prepared using waste wood particles, and good mechanical and physical properties. These composites were prepared by filling the waste wood particles into the polymers using different fabrication methods such as extrusion, hand layup, compression moulding, injection moulding and additive manufacturing (3D printing). A good number of research works have been reported on the testing and characterization of wood composites for the various applications so far. This fact motivated to prepare a state-of-the-art review on the recent developments in processing, characterization, and applications of wood composites. This paper presents a discussion on the chemical structure and properties of different types of wood species. The mechanical, thermal and water absorption behaviour of thermosets, thermoplastics and biopolymers based wood composites have also been discussed. Further, characterization of the nano biocomposites prepared using nanocellulose/nanoparticles of wood are also presented. The outcomes of the present review provide a good understanding of wood composites that will encourage the researchers for further research works & developments of novel wood composites for the advanced applications.     

Interfacial adhesion and shear behaviors of aramid fiber/polyamide 6 composites under different thermal treatments

Aramid fiber (AF) reinforced by polyamide (PA) composites are excepted to have good interfacial matching due to their similar chemical interactions of hydrogen bonding. Thus, polarizing optical microscope (POM), transverse fiber bundle (TFB) test, and droplet micro-debonding technique were respectively performed to characterize interfacial crystallization, adhesion and shear behaviors of AF/PA6 composites with different thermal treatments. Both interface adhesion and AF fibrillation are enhanced with decreasing cooling rate or increasing annealing temperature due to the increased interfacial transcrystallization interaction. However, fast cooled interface also presents a high interfacial shear strength (IFSS) due to favorable normal residual stress. The apparent IFSS is believed to be a result of competition between crystallization enhancing interfacial interaction, interfacial mismatching aggravating debonding, and an uncertain residual stress positive or negative for load transfer. TFB failure mechanism including AF fibrillation and kinking are schematically presented. Fibrillation strength of AF is found to follow Weibull distribution evaluated by droplet micro-debonding technique.     

Mechanical and thermal properties of Acacia leucophloea fiber/epoxy composites: Influence of fiber loading and alkali treatment

In this work, the influence of fiber content and alkali treatment on the mechanical and thermal properties of Acacia leucophloea fiber-reinforced epoxy composites was studied. Ten composite samples were fabricated by varying fiber content (5, 10, 15, 20, and 25 wt%); both untreated and treated fiber were soaked in a 5% NaOH solution for 45 min by using hand-layup method. The composite reinforced with 20 wt% treated fiber content exhibited better mechanical properties and thermal properties. Fourier transform infrared analysis, morphological analysis by atomic force microscope, and scanning electron microscope of composites were also performed.     

A review on flammability of epoxy polymer,cellulosic and non‐cellulosic fiber reinforced epoxy composites

Natural fiber is well‐known reinforcement filler in polymer‐matrix composites. Composite components like organic polymers and natural fibers are natural fire conductors as the natural fiber consists of cellulose, hemicellulose, and lignin, and hence are as highly flammable as wood. Natural fiber reinforced composite materials are progressively being used in a variety of applications where their fire response is a hazardous consideration, for example, in the automotive (transportation) and building‐construction industries. As a result, an awareness of their performance or response during a fire and the use of conventional fire retardants are of great importance, as they are subject to thermal decomposition when exposed to intensive high heat or fire sources. In this review paper, fire flammability is the main concern for cellulosic and non‐cellulosic fiber‐reinforced polymer composites, especially epoxy composites. This paper reviews the literature on the recent developments in flammability studies concerning polymers, epoxy polymers, cellulosic‐fibers, and non‐cellulosic fiber‐reinforced epoxy bio‐composites. The prime objective of this review is to expand the reach of “fire retardants for polymer materials and composites” to the science community, including physicists, chemists, and engineers in order to broaden the range of their applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Studies on polymers and composites from lignin and fiber derived from sugar cane

Sugarcane fiber (i.e. bagasse) lignin has a larger fraction of aromatics unsubstitution in the ortho position than hardwood or softwood lignin and hence has the greater ability to be derivatized. Furthermore, organosolv lignin has a higher purity than sulfonated and kraft lignins. This work examines the purification of organosolv lignin derived from bagasse and the physico‐chemical properties of the lignin and lignin‐phenol formaldehyde (PF) resin coatings, and composites. The wetability tests have shown that lignin and lignin‐PF resin films are effective water barrier coatings, though the contact angles of lignin‐PF resin films were considerably less than the wax films. The overall mechanical properties (i.e. peak stress, peak strain and modulus) of the bagasse fiber composites were lower than the values obtained with the composites without the inclusion of bagasse fiber. Copyright © 2007 John Wiley & Sons, Ltd.     

Study on structure and performance of surface‐metallized carbon fibers reinforced rigid polyurethane composites

The simultaneous promotion in mechanical and electrical properties of rigid polyurethane (RPU) is an important task for expanding potential application. In this work, carbon fibers (CFs) reinforced RPU composites were prepared with the goal of improving mechanical and electrical properties. Metallized CFs meet our performance requirements and can be easily achieved via electrodeposition. However, the weak bonding strength in fiber‐metal‐RPU interface restricts their application. Inspired by the reducibility and wonderful adhesion of dopamine (DA), we proposed a new and efficient electrochemical method to fabricate metallized CFs, where DA polymerization was simultaneously integrated coupled with the reduction of metal ions (Ni²⁺). The characterization results helped us to gain insight about the reaction mechanism, which was never reported as far as we know. Compared with pure RPU, the tensile, interlaminar shear and impact strength of polydopamine (PDA)‐nickel (Ni) modified CFs/RPU composites were improved by 11.2%, 21.0%, and 78.0%, respectively, which attributed to the strong interfacial adhesion, including mechanical interlocking and chemical crosslinking between treated CFs and RPU. In addition, the PDA‐Ni surface treatment method also affected the dispersion of short CFs in the RPU, which increased the possibility of conductor contact and reduced insulator between fibers networks, resulting in higher electrical conductivity.     

The effect of water immersion and fibre content on properties of corn husk fibres reinforced thermoset polyester composite

This work presents an experimental investigation into the effect of cornhusk fibre (CHF) content upon the mechanical properties, water absorption behaviour, and swellability of CHF/polyester (PE) composites used in water environments. The CHF/PE was prepared at different volume fractions using hot compression (~175 °C). To investigate the rate of water absorption and swellability behaviours, composites were immersed in water for varying durations. The mechanical properties of composites (i.e. tensile, bending and compression strengths) immersed in water were carefully evaluated. The results indicate that the composites with an increased CHF content and a longer immersion time are prone to lower mechanical properties. The large amount of water absorbed by the composite reduces the bonding interface between CHF and PE, which is responsible for the damage. Moreover, the amount of water absorbed and the swellability increase with a corresponding increase in the CHF content. The lowest water absorption (2.39%) was detected in 20% CHF and 80% PE composite immersed for 6 days. The findings gathered in this research endorse CHF/polyester thermoset composites as a viable alternative for construction applications.     

Effect of thermal cycling and open-hole size on mechanical properties of polymer matrix composites

This paper investigates the effects of thermal cycling on mechanical degradation of polymer matrix composites (PMCs). Un-notched and open-hole specimens are tested using developed thermal cycling apparatus and tensile test machine. In addition, the hole-size effect of open-hole tension glass/epoxy composite laminates is investigated. The tensile strength, mass loss and surface degradation of the specimens were obtained during 250 cycles. Experimental results showed that the holes diameter is the main parameter to control the thermal cycling effects on open hole structure. Also, it is found that laminates with smaller holes have higher tensile strength variation than those with larger holes. The results showed that increment of the hole diameter and number of cycles decreases the tensile strength.     

Analytical review of some relevant methods and devices for the determination of the specific volume on thermoplastic polymers under processing conditions

This article reviews some of the most representative methods and devices to measure the specific volume in polymeric materials found in literature. Each method is described and a comparison between the experimental conditions and typical injection molding processing conditions is discussed. In general, the main difficulty with specific volume measurements is determination of the temperature distribution through sample thickness, particularly when achieving typical processing conditions is intended. Therefore, the necessity of developing a new device which allows direct measurements of pressure and temperature at various positions along the sample thickness in order to calculate the cooling condition was identified.     

Environmental effects on fibre reinforced polymeric composites: Evolving reasons and remarks on interfacial strength and stability

The interface between fibre and matrix of fibrous polymeric composites is most critical and decisive in maintaining sustainability, durability and also reliability of this potential material, but unfortunately a comprehensive conclusion is yet to meet the label of confidence for the engineering viability. Fiber reinforced polymer (FRP) composites are being accepted and also utilized as better and reliable alternative materials for repairing and/or replacing conventional materials, starting from tiny objects to mega structure in various engineering applications. The promise and potential of these materials are sometimes threatened in speedy replacement of conventional materials because of their inhomogeneities and inherent susceptibility to degradation due to moist and thermal environments. Environmental conditioning is traditionally believed to be a physical phenomenon but present literature has revealed that the interdiffusion between fiber and polymer matrix resin comprises of physical, chemical, mechanical, physico-chemical and mechano-chemical phenomena. The failure and fracture behavior at ambient conditions itself is a complex phenomenon till at present. The service conditions which are mostly hygrothermal in nature, along with a variation of applied loads make the mechanical behavior nearly unpredictable, far off from conclusions in evaluating the short term as well as long term durability and reliability of FRPs. It is essential to accurately simulate the initial and subsequent evolution process of this kind of damage phenomena, in order to explore the full potential of the mechanical properties of composite laminates. The present review has emphasized the need of complying scattered as well as limited literature on this front, and has focused on creating the urgency to highlight the importance of judicious uses of these materials with minimum safety factors with an aim to achieving lighter weight in enhancing specific properties.     

Strength and toughness of carbon fibers reinforced rigid polyurethane composites by adsorbing tannic acid and refining Ni grains on carbon fibers surface

In this article, short carbon fibers (CFs) reinforced rigid polyurethane (RPU) composites were prepared with the aim of improving both strength and toughness. A tannic acid (TA)‐nickel (Ni) composite coating was spontaneously co‐deposited onto CFs surface by a one‐step electrodeposition method to strengthen the interface bonding of the composites. The satisfactory mechanical properties of the composites were mainly attributed to the superior interfacial adhesion. On the one hand, TA could play a role in refining Ni grain during electrodeposition. On the other hand, the hydroxyl groups attached to composite coating, which were introduced by TA, could react with the RPU matrix to form chemical bonds. When the composites were under stress, the chemical bonds could effectively transfer the stress from matrix to the interface, while the refined Ni crystals could greatly increase the stress transfer path, and thus improve the strength and toughness of the material. Compared with pure RPU, the tensile strength, bending strength,interlaminar shear strength, and impact strength of TA‐Ni‐coated CFs/RPU composites were improved by 14.8%, 83.1%, 28.7%, and 121.4%, respectively.     

Interfacial studies on the ozone and air‐oxidation‐modified carbon fiber reinforced PEEK composites

In this work, ozone modification method and air‐oxidationwere used for the surface treatment of polyacrylonitrile(PAN)‐based carbon fiber. The surface characteristics of carbon fibers were characterized by XPS. The interfacial properties of carbon fiber‐reinforced (polyetheretherketone) PEEK (CF/PEEK) composites were investigated by means of the single fiber pull‐out tests. As a result, it was found that IFSS (interfacial shear strength) values of the composites with ozone‐treated carbon fiber are increased by 60% compared to that without treatment. XPS results show that ozone treatment increases the amount of carboxyl groups on carbon fiber surface, thus the interfacial adhesion between carbon fiber and PEEK matrix is effectively promoted. The effect of surface treatment of carbon fibers on the tribological properties of CF/PEEKcomposites was comparativelyinvestigated. Experimental results revealed that surface treatment can effectively improve the interfacial adhesion between carbon fiber and PEEK matrix. Thus the wear resistance was significantly improved. Copyright © 2009 John Wiley & Sons, Ltd.