Superior Specific Properties Research Articles

Synergetic improvement of interlaminar fracture energy in carbon fiber/epoxy composites with nylon nanofiber/polycaprolactone blend interleaves

Carbon fiber/epoxy (CF/EP) composites are highly utilized materials for many applications in aeronautical and aerospace structures because of their superior specific mechanical properties. However, delamination between adjacent plies remains a major problem owing to the inherent brittleness of epoxy matrix. In the present work, PA66 nanofiber/PCL blend films were used as interleaves to increase the interlaminar fracture energy of CF/EP composites. PA66 nanofibers maintained their one-dimensional structure during epoxy curing, while PCL first melted and then mostly phase-separated from epoxy. It was found that modes I and II fracture energies of the laminates interleaved with PA66 nanofiber/PCL blend films were increased significantly by 110% and 101%, respectively, demonstrating a synergistic effect. At the same time, the flexural strength and flexural modulus of the CF/EP laminates were unchanged. DMA tests confirmed better interfacial adhesion between PA66 nanofibres and epoxy when PCL was added. Blend interleaves with nanofibres embedded in a polymer matrix with a low melting point provide a new route to synergetic enhancement of the delamination fracture energies of CF/EP laminates.

Mathematical modelling of laser ablation of random oriented short glass fiber reinforced Polyphenylene sulphide (PPS) polymer composite

Many sectors using high technology need to use materials with more than one property. Reinforced plastics (FRP) have been used frequently in the transportation and energy sectors because of its superior specific mechanical properties especially high strength-to-weight ratio. Lasers are often used in cutting, drilling and surface treatments since they have the ability to perform high energy transfer in various forms. Because of the quality degradation in the laser process, especially in the efficient processing of FRPs, high energy and other laser parameters compatible with these energy levels are required. Thermal damage is one of the most important parameters affecting the quality of FRPs.Mathematical Modelling of laser ablation of random oriented short glass fiber reinforced plastic were performed. Temperature distribution equation has been obtained by Fourier method. Finite difference method was applied to simulate temperature distribution and Heat affected Zone (HAZ) size on FRP surface. Temperatures at any distance from laser spot were obtained by solving one-dimensional heat conduction equation. The melting and vaporization temperatures of PPS were used as boundary conditions to find Fourier coefficients in the temperature distribution equation. In order to test the reliability of the proposed mathematical model, laser pulses of different energies were sent to the material. As a result of the measurements made from the obtained cavities, the reliability of the proposed model has been proven.

Concurrent design and manufacture of a thermoplastic composite stiffener

Fibre reinforced composite materials are finding increasing application in aerospace structures due to their superior specific properties. Aerospace structures make widespread use of stiffening elements, such as stringers, for example in wingboxes and fuselage structures. Sizing of stiffeners to fulfil strength, stiffness and manufacturing considerations is a significant challenge. Herein, a novel manufacturing approach using winding in combination with laser-assisted tape placement is used to manufacture an omega-shaped stiffener made from carbon fibre thermoplastic material. This paper discusses the integrated approach taken by considering material choice, manufacturing constraints and structural design on the performance of a closed-section omega stiffener. The sizing is based on the buckling response of the wingbox, with manufacturing constraints taken into consideration. In the collapsible mould, a low-melt aluminium alloy is used as a spacer, which can be removed post-process by exposing the mould to the alloy melt temperature, which is below the glass transition temperature of the thermoplastic composite material. Manufacturing tests show that repeatable stiffeners of the appropriate dimensions are manufactured. Characterisation tests show that both the bond strength, measured using an interlaminar shear strength test, and the corner strength, assessed using a four-point bend test, are satisfactory.

Biocomposites based on plant material

Fibre reinforced composite materials offer superior specific mechanical properties in reference to their weight. In the past years, composite materials such as carbon or glass reinforced plastics (CFRP or GFRP) are used increasingly in all sectors of transportation and for industrial or leisure products. The composite consists of a load bearing fibre architecture, usually in the form of a continuous fabric architecture, and an embedding matrix, usually a thermoset such as epoxy. With regard to the energy efficiency and carbon footprint, due to their lightweight nature, these composite materials in general offer interesting properties, if applied in long-term operations. However, the raw materials used for the production of both typical fibre materials and thermoset resins are still based on crude oil, and the refining and processing up to the semi-finished good consume a significant amount of embodied energy. In this study, composites made of glass or flax fibres and resin systems based on condensed tannin and furfuryl alcohol, both extracted or derived from plant tissues, were manufactured using vacuum infusion (VI) and resin transfer moulding (RTM) processes. The results show that mechanical properties close to common fiber/resin combinations like glass fiber and epoxy or phenolic resins can be reached by these materials.

Mechanical behaviour of A356 alloy reinforced with high strength alloy particulate metallic composites

In the present investigation, work has been carried out to fabricate composites with high strength and good ductility by maximizing a uniform and smooth interface for effective transfer of load, and minimizing reinforcement cracking, agglomerations, and pull outs. A high-strength alloy (ternary) in particulate (HSA(P)) form was used as reinforcement in 356 aluminium. A 356-HSA(P) composite was prepared using the stir casting technique by dispersing an average particle size of 125 µm for reinforcement with various weight fractions varying between 5% and 15%. Secondary processing was done using the hot extrusion process to obtain 14 mm Ø rods (extrusion ratio of 18:1) and homogenized in an industrial furnace for 24 h. A decrease in reinforcement size was observed with increments in particulate content. The hardness of the composites was improved compared to the existing matrix. Mechanical properties such as UTS, yield strength, modulus of elasticity and ductility reveal superior specific properties than that of the alloy.

Composite Peening - A Novel Processing Technology for Graded Reinforced Aluminium Matrix Composites

Recently, the attention paid to Metal Matrix Composites (MMCs) has increased markedly. In particular, particle-reinforced MMCs are outstanding due to superior specific properties and their wear resistance. In order to further improve material utilization, recent investigations with local reinforcements in highly stressed component sections, the so-called Functionally Graded Metal Matrix Composites (FGMMC), are concerned. The production of such FGMMC was realized with composite peening - a modified process on the basis of micro shot peening. Due to this solid-phase process, ceramic particles can be introduced into regions close to the boundary layer. As preliminary studies on tin show, ceramic particles can be introduced close to the specimen surface even at room temperature. By varying process parameters, in particular by increasing the temperature, the penetration depth of the particles can be significantly increased. In case of aluminium as base material, an input of particles into the surface could be observed at a process temperature of 150 °C. The combination of aluminium with reinforced ceramic particles makes this process interesting for lightweight, wear-resistant and cyclically highly stressed structural components. Using composite peening to produce FGMMCs is a novel, economic approach.

High Performance Magnesium Based Composites Containing Nano-Length Scale/Amorphous/Hollow Reinforcements

Magnesium is the lightest weight metallic material that can be used in multiple engineering applications and biomedical sector as a structural material. It is abundantly available in earth’s crust and sea water and non-toxic in nature. Inherent to magnesium is its superior specific mechanical properties, high damping, electromagnetic shielding capability and ability to reduce carbon signature of the transportation sector.Magnesium is one of the widely available metal in earth crust and sea water. It is non-toxic and hence does not pose a health risk during recycling or waste dumping in natural water bodies. As a result, magnesium technology is sustainable and beneficial to planet earth and living organisms.Magnesium based materials are gradually being used in many applications and their performance and applications can further be stretched using the composite technology. Accordingly, the main scope of this paper is to highlight the enhancement of a number of properties of magnesium through the use of nanolength scale, amorphous and hollow reinforcements.

Light iron and hard magnesium nanocomposites

The focus of this work is on creating bulk nanocomposite materials by combining iron and magnesium. The procedure requires the synthesis of Mg2FeH6 hydride by ball milling followed by the desorption of hydrogen assisted by spark plasma sintering. The nanostructured hybrids of iron and magnesium thus obtained exhibit superior specific properties and fill holes in the materials properties space for light alloys. The idea that is outlined opens up new opportunities toward the synthesis of intimate mixture at the nanoscale of elements exhibiting repulsive interactions.

A novel p–n junction Ag3PO4/BiPO4-based stabilized Pickering emulsion for highly efficient photocatalysis

This study demonstrates a new kind of photocatalytic system via utilization of the superior specific properties inherent in Pickering emulsions.

Finite Element Analysis of Jute Fibre Made Hybrid Polymer Matrix Composite

During last few years, the interest in using natural fibers as reinforcement in polymers has increased significantly. Natural fibers are not only strong and lightweight but also relatively very cheap and bio-degradable. In this work, an investigation is carried out on jute fiber, a natural fiber. Jute fiber has gained interest in the composite field due to its superior specific properties compared to manmade synthetic fibers like glass, Kevlar, asbestos, etc. The present work describes the development and characterization of natural fiber based composites consisting of jute fiber as reinforcement and hybrid resin consisting of general purpose resin and cashew nut shell resin as matrix material. The composites are fabricated using hand lay-up technique. The tensile strength is studied using experimental and numerical analysis. The nature of hybrid matrix at different composition is also studied. The commercial Finite Element Analysis software ANSYS is used for numerical study.

Dry sliding wear behaviour of zinc oxide reinforced magnesium matrix nano-composites

The main objective of the present work is to investigate the dry sliding wear behaviour of a magnesium matrix composite reinforced with zinc oxide nano-particles. Magnesium matrix composites have many applications, especially in the automotive and aerospace industries, due to their superior specific properties. A magnesium matrix composite with 0.5vol.% ZnO nano-reinforcement was prepared using powder metallurgy and was hot extruded to eliminate pores. The wear behaviour of the Mg/ZnO nano-composite was investigated by conducting dry sliding tests as a function of wear with an oil-hardened non-shrinking (OHNS) steel disc as the counterpart on a pin-on-disc apparatus. Wear tests were conducted for normal loads of 5, 7.5 and 10N at sliding velocities of 0.6, 0.9 and 1.2m/s at room temperature. The variations of the friction coefficient and wear rate with the sliding distances (500m, 1000m and 1600m) for different normal loads and sliding velocities were plotted and analysed. To study the dominant sliding wear mechanism for various test conditions, the worn surfaces were analysed using scanning electron microscopy. The wear rate was found to increase with the load and sliding velocity.

Finite Element Analysis of Jute and Banana Fibre Reinforced Hybrid Polymer Matrix Composite and Optimization of Design Parameters Using ANOVA Technique

During last few years, the interest in using natural fibers as reinforcement in polymers has increased significantly. Natural fibers are not only strong and lightweight but also relatively very cheap and bio-degradable. In this work, an investigation is carried out on jute fiber, a natural fiber. Jute fiber has gained interest in the composite field due to its superior specific properties compared to manmade synthetic fibers like glass, Kevlar, asbestos, etc. The present work describes the development and characterization of natural fiber based composites consisting of jute fiber as reinforcement and hybrid resin consisting of general purpose resin and cashew nut shell resin as matrix material. The composites are fabricated using hand lay-up technique. The tensile strength is studied using experimental and numerical analysis. The nature of hybrid matrix at different composition is also studied. The commercial Finite Element Analysis software ANSYS is used for numerical study.

Tensile Behavior of Environment Friendly Jute Epoxy Laminated Composite

Jute fiber has gained interest in the composite field due to its superior specific properties compared to manmade synthetic fibers like glass, kevlar, asbestos, etc. In this study, jute composites were made with the vacuum assisted resin infiltration (VARI) techniques having jute fiber preform staking sequences (0/0/0/0), 0/+45°/-45°/0 and 0/90°/90°/0. For all cases, a total of 25% volume fraction of jute fiber was incorporated. The developed composites were characterized by tensile and three point bend tests and the experimental results thus obtained were compared with that of the theoretical values. After both mechanical tests, fracture surfaces were cut and observed under high resolution FEG SEM (field emission gun scanning electron microscopy). In the case of 0/0/0/0 and 0/+45°/-45°/0 laminate, longitudinal tensile strength has been found to be higher than that of the transverse direction. However, for 0/90°/90°/0 laminate, tensile strength in both directions have been found to be very close to each other. For all developed composites, experimental results revealed that the tensile properties of the developed composites are strongly dependent on the tensile strength of jute fiber and that the tensile properties of jute fiber are very much defect sensitive. Finally, initiative has also been taken to discuss the mechanical behaviors of the composites in terms of the fracture morphologies observed under the SEM.

Effect of Fiber Orientation on the Tensile Properties of Jute Epoxy Laminated Composite

Jute, the pride of Bangladesh, has gained interest in the composite field due to its superior specific properties compared to artificial manmade fibers like glass, kevlar, etc. In this study, jute composites made with the vacuum assisted resin infiltration (VARI) techniques were investigated. Jute fiber preform stacking sequences were (0/0/0/0), 0/+45°/-45°/0 and 0/90°/90°/0. For all cases, a total of 25% volume fraction of jute fiber was incorporated. The developed composites were characterized by tensile tests and the experimental results thus obtained were compared with that of the theoretical values. After tensile tests, fracture surfaces were cut and observed under high resolution FEG SEM. In the case of 0/0/0/0 and 0/+45°/-45°/0 lamina composites, longitudinal tensile strength has been found to be higher than that of the transverse direction. However, for 0/90°/90°/0 lamina composites, tensile strengths in both directions were very close to each other. For all developed composites, experimental results revealed that the tensile properties of the developed composites strongly depend on the tensile strength of jute fiber and that the tensile properties of jute fiber are very much defect-sensitive. Finally, a discussion of the tensile behaviors of the composites is initiated in terms of the fracture morphologies observed under the SEM.© 2013 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi: http://dx.doi.org/10.3329/jsr.v5i1.10519 J. Sci. Res. 5 (1), 43-54 (2013)

Mechanical and Dielectric Properties of PTSL FRP Composites

Utilization of natural fibers for making composites and employ them in various structural applications due to superior specific properties drawn the attention of researchers in the present scenario. In the present research a new natural fiber i.e. Palm Tree Sprout Leaf (PTSL) is introduced, and is extracted by a novel technique called pure splitting method. Untreated and chemically treated palm tree sprout leaf fiber are reinforced into the polyester matrix for fabricating composites and are tested for determining their mechanical and dielectric properties as per ASTM procedures. Morphological characterization of fiber is also done using Scanning Electron Microscope. Tensile strength and modulus, flexural strength of chemically treated PTSL fiber reinforced polyester composites exhibited a reasonable improvement when compared with the untreated fiber reinforced polyester (FRP) composites. Flexural modulus of PTSL FRP composites is more when compared with chemically treated FRP composites at all volume fractions of fiber. Impact strength of PTSL FRP composites clearly increased with increase in fiber volume fraction. The reasonable values of dielectric strength at various fiber volume fractions exhibited by PTSL FRP composites will give an opportunity for designer in choosing light weight insulating material.

Mechanical behaviour of hollow-tube stackings: Experimental characterization and modelling of the role of their constitutive material behaviour

Architectured cellular materials are very promising as lightweight aeronautical frames thanks to their superior specific mechanical properties such as structural or impact resistance. However, because of the processing routes and heat treatments used in the production process, the material within the cell walls may behave differently from the bulk, and therefore the in situ mechanical properties are often unknown. The present work aims at exploring the influence of the constitutive material behaviour on effective mechanical properties of cellular materials. To address this issue, small brazed sandwich structures with hollow-tube stacking cores have been considered as “model” materials. Compression tests have been performed on these structures, coupled with a detailed analysis of microstructures resulting from brazing heat treatments. Also, tensile tests on isolated tubes and microindentation tests have been conducted in order to have access to in situ constitutive mechanical properties. Experimental data have then been introduced in a finite-element modelling of those sandwich structures. Based on the modelling, different mechanical behaviours have been assumed for the constitutive material. Various degrees of modelling extension have been considered, introducing progressively a specific behaviour for brazes and accounting for the damage and cracks observed experimentally around braze extremities. Their influence on the effective behaviour of the stackings is discussed in detail.

Microstructure and Properties of Stir Cast AZ91 Mg Alloy – SiC<sub>p</sub> Composites

Magnesium metal matrix composites (MMCs) have been receiving attention in recent years as an attractive choice for aerospace and automotive applications because of their low density and superior specific properties. Using stir casting process, AZ91 magnesium alloy metal matrix composites have been produced with different weight percentages (5, 10, 15, 20 and 25) of silicon carbide particles (SiCp) addition. Microstructural characterization reveals uniform distribution of SiC particles with good interfacial bonding between the matrix and reinforcement. Electrical conductivity and Co-efficient of Thermal Expansion (CTE) measurements carried out on these composites have yielded better properties. Improved mechanical properties such as hardness, ultimate tensile strength, and compressive strength are obtained. The microfracture mechanisms involved during tensile fracture is analyzed and correlated with the properties obtained.

Carbon fibre-reinforced plastic truss structures for satellite using braiding/resin transfer moulding process

Surveillance satellites require dimensional stability against temperature variation since the performance of precision optical devices depends on dimensional stability. Dimensional stability can be improved by decreasing the linear thermal expansion of truss structural parts. In this study, a whole truss structure was produced, consisting of several structural units including joints made by using a braiding/resin transfer moulding (RTM) process. Our braiding technologies with a robotic mechanism are capable of braiding not only straight tubes but also divaricate configurations such as of tri-axial truss joints. Braided carbon fibre preforms were moulded using an RTM process with polycyanate resin in order to investigate the mechanical properties and coefficient of linear thermal expansion. Braided carbon fibre-reinforced plastic (CFRP) truss joints and truss structures were produced as examples of aerospace applications by using the braiding/RTM process, in order to evaluate their mechanical properties and carry out structural testing. The modulus and stiffness of braided CFRP truss joints and truss structures were evaluated by comparison with aluminium (Al) and titanium (Ti) alloys. It was clarified that CFRP truss joints have superior specific mechanical and thermal properties as compared to the conventional materials such as Al and Ti alloys. The CFRP truss joint makes the truss structure construction lighter.

An overview of the technology of fibre-reinforced plastics for design purposes

Fibre-reinforced plastic materials or composites are recognised as possessing superior specific properties when compared to conventional engineering materials. However, the widespread use of these materials is still limited, with engineering designers choosing to stick with what they know best. This unfortunately tends to stifle innovation and leads to sub-optimal solutions. This article provides a simplified introduction to the technology of fibre-reinforced thermosetting plastics from the perspective of the information requirements of engineering designers. The use of detailed descriptions has been kept to a minimum and a concentration on the most regularly used material types, properties and manufacturing processes. The aim of this article is to help engineering designers, who are not familiar with this technology, obtain a reasonable understanding and sufficient knowledge to pursue relevant topics further.

Impact damage detection in filament wound tubes using embedded optical fibre sensors

Filament wound tubes are currently being used extensively in service because of their superior specific properties and the relatively simple manufacturing technique involved in their production. However, filament wound tubes can suffer from low-velocity impact damage () during service. Such damage can result in poor post-impact properties which in certain applications can reduce the burst strength below safe working levels. This paper discusses the use of embedded optical fibre sensors for impact damage detection in filament wound tubes. The primary aim was to detect threshold levels of impact damage which would render the tube unsafe to use. Two types of sensor were used, namely (i) a simple crack detection system where the fracture of the optical fibres was correlated to the level of impact damage and (ii) a novel intensity-based optical fibre sensor which was used to measure the stiffness change in the filament wound tube as a function of impact damage. The first sensor was designed to be used on-line, i.e., during service, whereas the second sensor was designed for off-line analysis to provide more detailed information about the extent of impact damage. This study has demonstrated that it is relatively straightforward to embed the optical fibres into the filament wound tube during its manufacture. The majority of the optical fibres survived the filament winding and subsequent processing operation. The feasibility of using the simple crack detection system was successfully demonstrated. A novel intensity based optical fibre sensor was used to measure the stiffness change in the composite as a function of impact damage.