Lightweight Composite Materials Research Articles

A study on fabrication of monolithic lightweight composite electronic housing for space application

This paper dealt with an alternative approach of enhancing mass savings in spacecraft avionics design by replacing conventional aluminum alloy housing widely used for various spacecraft avionics with lightweight composite materials. For this purpose, key design requirements were defined to build up composite housing with various functionalities as well as more lightweight characteristics as compared with aluminum alloy housing. The proposed composite housing can be equipped with multiple electronics boards; and it can provide mechanical and electrical interfaces with ease. A fabrication process was also designed to overcome low machinability of CFRP and to minimize the post-treatment such as machining CFRP after curing. In addition, the composite housing with monolithic grid-stiffened frame was fabricated by co-curing through vacuum bag molding method. Its physical properties were also investigated with regard to launch environmental random load, stiffness, thermal conductivity, EMI protection. As a result, it was shown that the composite housing can have good performance comparable to aluminum and provide the mass savings over the aluminum housing having the same dimension. The proposed concept for composite electronic housing will be an effective alternative for lightweight avionics design for space application.

Extrusion of Softwood Kraft Lignins as Precursors for Carbon Fibres

There is much interest in using less expensive raw materials as precursors for carbon fibre manufacture to increase the utilisation of strong, light-weight composite materials in the transportation sector. One such potential raw material is lignin. Most studies exploring melt spinning of lignin have used lignins from organosolv or hardwood kraft delignification processes. There has been little success reported in utilisation of the more commercially available softwood kraft lignins. In this study, lignins from different softwood kraft cooking processes were investigated with respect to their melt spinning performance and conversion to carbon fibres. The isolated lignins differed mainly in molecular weight, glass transition temperature, and softening temperature. All of the lignins produced from the laboratory cooks could be extruded without any plasticizer addition. However, the lignins contained volatiles that resulted in bubbles being formed along the length of the fibres. After vacuum drying, at elevated temperatures to remove volatiles, only the lignin originating from conventional kraft cooking was able to be melt extruded without plasticiser addition; this lignin had the lowest molecular weight amongst the samples. The stabilisation and carbonisation of these fibres gave carbon fibres with strengths comparable to those produced from lignins of other origins.

Thermoforming and Structural Analysis of Combat Helmets

To reduce combat casualties, military helmets are designed to provide protection against projectiles. Modern combat helmets are constructed of relatively lightweight composite materials that provide ballistic protection to the soldier. The manufacture of most composite helmets is labor intensive and involves the manual application and smoothing of individual layers of reinforcement to a concave mold surface. The recently developed double diaphragm deep drawing thermoforming process turns as-purchased, flat-form composite materials into structurally efficient three-dimensional shapes. Using this process, prototype shells have been produced and subsequently tested structurally. The success of the outcome has been greatly assisted through the use of specialized virtual prototyping techniques to provide insight into the thermoforming process of the shells and subsequently their structural performance by accounting for the actual fiber orientations of those finished shells.

Mechanical characterization and validation of poly (methyl methacrylate)/multi walled carbon nanotube composite for the polycentric knee joint

Trans femoral amputation is one of the most uncomfortable surgeries in patient׳s life, where the prosthesis consisting of a socket, knee joint, pylon and foot is used to do the walking activities. The artificial prosthetic knee joint imitates the functions of human knee to achieve the flexion–extension for the above knee amputee. The objective of present work is to develop a light weight composite material for the knee joint to reduce the metabolic cost of an amputee. Hence, an attempt was made to study the mechanical properties of multi walled carbon nanotubes (MWCNT) reinforced Poly (methyl methacrylate) (PMMA) prepared through melt mixing technique and optimize the concentration of reinforcement. The PMMA nanocomposites were prepared by reinforcing 0, 0.1, 0.2, 0.25, 0.3 and 0.4wt% of MWCNT using injection moulding machine via twin screw extruder. It is observed that the tensile and flexural strength of PMMA, which were studied as per ASTM D638 and D790, respectively, were increased by 32.9% and 26.3% till 0.25wt% reinforcement of MWCNT. The experimental results of strength and modulus were compared with theoretical prediction, where a good correlation was noted. It is concluded that the mechanical properties of PMMA were found to be increased to maximum at 0.25wt% reinforcement of MWCNT, where the Pukanszky model and modified Halpin-Tsai model are suggested to predict the strength and modulus, respectively, of the PMMA/MWCNT composite, which can be opted as a suitable materiel for the development of polycentric knee joint.

Mechanical Behaviour of Sugarcane Bagasse and Banana Fibers Reinforced Composite

The present work investigates the effect of hybridization of sugarcane bagasse and banana fibers as reinforcements in the polymer matrix. Composites made from natural fibers possess favourable properties like low cost, light weight, high strength and eco-friendly nature compared to synthetic fibers. Structural applications such as aerospace and automobile industries moving towards the use of these natural composites. In this research work two lightweight composite materials were developed, one with a linear pattern and other with chopped pattern of sugarcane bagasse and banana fiber reinforcements. The developed composites were subjected to different tests to investigate their mechanical behaviour. Both the developed specimens were investigated for their tensile strength, hardness, and water absorption capacity and compared their behaviour. It is observed from the test results, the composite with the chopped fiber reinforcement possess better mechanical properties compared to the linear reinforcement.

Battle for the skies [jet engine

In the airline business, margins are everything. Large modern jet engines make up a huge proportion of an aircraft's weight, and the fuel used is a huge part of an operator's costs. A reduction in either could be the difference between profit and loss. Fluctuating oil prices, fierce competition and challenging carbon reduction targets set by regulators are all increasing pressure on manufacturers to improve engine efficiency. The world's 'big three' jet engine builders - General Electric (GE), Rolls-Royce and Pratt & Whitney - have all responded, unveiling new ranges of engines packed full of innovative technology and engineering. Speed here isn't the most important thing - in fact, the engines will operate at similar speeds to those in service today. It's all about improving efficiency, minimising the environmental impact and - most importantly - reducing operating cost. Using lightweight but ultra-tough composite materials, advanced high-pressure compressors, new planetary gearing systems and even 3D-printed components, competition is hotting up in a worldwide commercial engine market that in 2013 was estimated to have reached around $25bn.

Optimisation of an air film cooled CFRP panel with an embedded vascular network

The increasing use in the aerospace industry of strong, lightweight composite materials in primary structural components promises to substantially reduce aircraft non-pay-load weight, improving fuel consumption and operating profitability. This study explores the extension of composite material to regions of gas turbine engines previously considered too hot for composites with moderate melting points. Throughout the majority of a gas turbine cycle, gas stream temperatures exceed the polymer composite glass transition by a considerable margin. Boundary layer cooling strategies, however, may be adopted in the compression stages to extend the downstream distance that can be constructed using lightweight composites. This paper presents formulation and validation of a numerical model and its use in an optimisation study to develop a systematic process for thermal design of polymer composite structures in ‘warm’ gas streams. Internal vascular and external boundary layer film cooling strategies are considered.

Design and fabrication with fibre-reinforced polymers in architecture: a case for complex geometry

Fibre-reinforced polymers (FRPs) are a family of strong and lightweight composite materials combining fibres and polymers. FRPs are widely used in the aviation, naval and automotive industries for components that require a high ratio of strength to weight and durability. Despite some pioneering experimental architectural applications in the 1960s, it is only in recent years that a growing interest in FRP elements is evident in the architectural field. The following paper critically reviews the current use of FRP in architecture and proposes a framework and a method to design and fabricate freeform architectural elements and structures from FRP without the need for using moulds. The proposed method is examined in a case study design and fabrication of a shading structure for beach areas. The case study results are discussed and conclusions are presented for future developments of the proposed method for the use of composite materials in architecture.

Yün Atık Kumaş Takviyeli Kompozitlerin Mekanik ve Termal Özellikleri

Today, felt and woven fabrics are used as a reinforcement material in textile composite structures. In these structures glass and carbon fibres are the widely used ones. However for almost a decade, researchers have also shown some interest on natural fibre reinforced composites. In this study, it has been aimed to use wool waste fabric to be able to produce a lightweight composite material. For this purpose, the composite samples were produced by using wool fabrics in warp direction together with their waste blends as a reinforced material. The produced reinforced wool composite structures were then tested for both their mechanical properties, i.e. Izod impact and tensile strength tests, and for their thermal properties. The fracture surfaces of the samples were also inspected on the scanning electron microscope. According to the results, it has been evaluated that wool fabrics and their waste may be used as a reinforcement material for the application of textile composites presenting in lightweight structures for the construction industry. The wool waste fabric reinforced composites’ mechanical properties can be improved by studying various waste percentages in future studies to gain better mechanical properties. The thermal conductivity of the composites was increased as the waste increases within the structure. As a result, wool waste materials can as well be used for future recycled textile materials in lightweight reinforced composites.

Effect of red mud filler on mechanical and buckling characteristics of coir fibre-reinforced polymer composite

Red mud produced as by-product in Bayer’s process for alumina production is posing severe environmental challenge in its disposal. Present work describes using this environmental pollutant as filler in combination with coir fibre using polyester resin for composite production. Tensile properties, flexural properties, compressive properties, hardness and density of coir polymer composites with and without red mud filler were evaluated experimentally. Subsequently, buckling analysis of the prepared composite was also done experimentally and using finite element method at different grid size and for different number of elements to establish the grid independence of obtained results. It has been observed that compressive strength, hardness and density of the prepared composite improved with addition of red mud as filler. This may be attributed to metallic oxides present in chemical composition of red mud. Addition of the filler had a negative effect on tensile and buckling properties as the load cannot be transferred effectively from fibre to resin. Interestingly, it has been observed that composite plates with 20 % fibre gave optimum combination of various properties. The main aim of this work was to study the effect of red mud filler on the mechanical properties and buckling strength of the prepared composites leading to development of a novel low-cost, light-weight composite material using an environmental pollutant which can be used for light-weight structural application.

Water Absorption Ratio and Flexural Strength Characteristics of Lightweight Composite Panel Surface Material Based on Addition Ratio of Powdery Modified Sulfur

Water Absorption Ratio and Flexural Strength Characteristics of Lightweight Composite Panel Surface Material Based on Addition Ratio of Powdery Modified Sulfur

Mussel-inspired polydopamine coated hollow carbon microspheres, a novel versatile filler for fabrication of high performance syntactic foams.

Syntactic foams, which can be synthesized by mechanical mixing of hollow microspheres with a matrix material, are a special class of lightweight composite materials. Developing of high-performance syntactic foams remains challenges. In this work, a facile and environmentally friendly surface modification method employing polydopamine (PDA) as a surface treatment agent for hollow carbon microspheres (HCMs) was used, aiming to extend the application of syntactic foams to seldom touched areas. The PDA coating was used as a strategy for interfacial interaction enhancement and also as a platform for further metal coating meant for electromagnetic interference (EMI) shielding. The stronger interfacial interaction between microspheres and polymer matrix provided effective interfacial stress transfer, as a result of the syntactic foams with high strength to weight ratio. Furthermore, the PDA coating on HCMs served as a versatile platform for the growth of noble metals on the surface of PDA-HCMs. Silver nanoparticles was grown by PDA medium. The silver coated HCMs (Ag-PDA-HCMs) impacted the complex permittivity of the syntactic foams leading to high EMI shielding effectiveness (SE). The specific EMI SE reached up to 46.3 dB·cm(3)/g, demonstrated the Ag-PDA-HCMs/epoxy syntactic foam as a promising candidate for lightweight high-performance EMI shielding material.

Application of Lightweight Composite Materials in Heavy Roadway

A membrane-beam-elastic element mechanical model of a lightweight composite heavy roadway, which is used on soft slimy ground, is built and its mechanical behaviors under loads are simulated by a large commercial finite element analysis software. The structural style which deformation is minimum under same loads is found, and numerical results are accorded with test ones, can meet the required precision and show reliability of the numerical calculation model. The commercial software can be used to simulate actual static strength situation of the lightweight composite heavy roadway and explore structural style of new roadway. Research shows that lightweight composite heavy roadway which can guarantee heavy vehicles pass in the soft slimy ground conditions make a significant technological breakthrough.

The Effect of Additives on Bending Strenght of Pultruded Hybrid Reinforced Resol Type Phenolic Composite

Pultrusion manufacturing process is a well established technique for the cost-effective production of high-modulus and lightweight composite materials having constant cross-sectional profiles. A study was carried out to analyze the effect of additives on bending strength of pultruded hybrid reinforced resol type phenolic composite. Glassfibre roving and kenaf fibre hybrid were reinforced in resol type phenolic. A series of bending tests were performed by varying the loading percentage of two type’s pultruded fibres,without additives and with additives. From the results, it was found that the modulus of strength of composites with additives display higher values as compared to composite without additives. The presence of additives were able to synergistically interact with both fibres and finally improve the interaction between them. Analysis of the fracture surface from the bending test were carried out using Dino-Lite digital microscope.

The Role of Materials Testing in Vehicle Lightweighting

Abstract Consumer demand for greater fuel efficiency and a changing regulatory environment have stimulated substantial interest in alternative materials for passenger vehicles. Automotive manufacturers now have a wide variety of choices available, ranging from various grades of steel and aluminum to the most advanced lightweight composite materials. This article describes testing innovations introduced to keep pace with the use of new materials in automobiles.

Effects of EPS bead inclusions on stress–strain behaviour of sand

ABSTRACT: Lightweight fill solutions have been used in many civil engineering projects throughout the world. At locations with poor soil conditions, alternative lightweight construction fill materials such as expanded polystyrene (EPS) geofoam, wood chips, and tyre wastes may be used instead of conventional fill materials. These materials are used as an additive for the soil. It is known that the type, aspect ratio and content of the admixtures have an important role in the mechanical properties of the mixtures. The main objective of this study was to assess the feasibility of the potential use of EPS beads in geotechnical applications. The effect of EPS bead gradation on the stress–strain behaviour of lightweight composite materials composed of EPS bead–sand mixtures (EPS–sand) was investigated through a series of triaxial compression tests under three different confining pressures. Three different types of spherical EPS beads with different unit weights (EPS-1, EPS-2, and EPS-3) were mixed with sand with varying EPS bead content. This study has shown that the deviatoric stress of a EPS–sand mixture is not only a function of volumetric EPS bead content but it also depends on EPS bead grain size distribution (EPS bead type). Whereas volumetric EPS bead content increases when all other variables are constant (EPS bead type in EPS–sand), the initial modulus of elasticity decreases linearly. Consequently, EPS bead inclusion did not enhance the maximum deviatoric stress of EPS–sand when compared with that of the sand-only specimen. However, bead addition provides a lightweight aspect to the mixture which can be attractive to use in many geotechnical engineering projects. EPS bead content, confining pressure and EPS bead type-dependent multiple linear regression (MLR) equations were proposed to estimate the initial undrained elastic modulus of EPS–sand to reduce the cost and time involved in conventional laboratory testing of EPS–sand mixtures. Based on the stress–strain behaviour of EPS–sand, these mixtures may be utilised in geotechnical applications as a lightweight fill material.

A fully coupled finite element-boundary element vibro-acoustic analysis for laminated composite structures with enclosed acoustic cavities

A major contribution of aircraft cabin noise is due to the vibrating airframe structure in which the use of lightweight composite materials is quite common. Due to the strong influence of such vibrating structures on the enclosing fluid, such as air, and vice-versa, a fully coupled analysis involving both the systems is necessary in many cases. Hence the present work details a fully coupled vibro-acoustic analysis of such type of flexible cavity subjected to the external mechanical excitation based on a coupled finite element (FE) and boundary element (BE) approach. The structural mode shapes and eigen frequencies are computed using the FE free vibration analysis of in-vacuo structures, which are subsequently coupled through the mobility equation with the acoustic part modeled with the BE method. The developed approach is also well compared with the fully coupled FE approach but the advantage derived here is that it is sufficient to model each domain independently thus reducing the problem dimension. The discussed method ensures full coupling between the two systems considering the cavity acoustic back pressure and also enables a fully coupled analysis of a double-walled structure attached to an acoustic cavity which resembles a true aircraft cabin.

Preparation and Study on the Waterproof Performance of Polystyrene Lightweight Composite Insulation Materials

In the experiment, polystyrene particles were used as lightweight aggregate to prepare lightweight composite insulation board which was mixed with fibers and waterproofing agent. The effect of water-cement ratio and volume ratio of polystyrene particles and cement on the density and mechanical properties of polystyrene insulation board was researched. And styrene-acrylic emulsion, stearic acid emulsion and composite emulsion waterproofing agent were used respectively to modify the waterproof of insulation board. Besides, the underlying action mechanism was explored. The results show that the optimum volume ratio was 5:1, and the optimum water-cement ratio was 0.45. And when the content of composite emulsion waterproofing agent was 8%, the 2h and 24h water absorption were 6.0% and 8.1% respectively.

Technological Parameters and Design of Bionic Integrated Honeycomb Plates

We investigated an integrated manufacturing method to develop lightweight composite materials. To design the preparation process for the integrated honeycomb plates, the shear and compressive mechanical properties of the corresponding composite materials were also investigated. The results indicate that these composite materials, with two types of resins reinforced by short basalt fibers, exhibit obvious toughness, particularly in their compressive properties. The Epoxy Resin (ER) is denser and has better bonding at the fiber and matrix interface than the vinyl ester resin matrix. Therefore, the ER exhibits better shear and compressive strengths than the vinyl ester resin matrix, thereby providing a design technology of the preparation process of the integrated honeycomb plate. The matrix material of this plate is composed of an epoxy (E51), a curing agent (593), and a thinner (501) at a ratio of 10:3:1; short basalt fibers are added as a reinforcing material at a 30% volume fraction. By increasing the curing temperature and other experimental conditions, we obtained an expected integrated honeycomb plate. This integrated honeycomb plate possesses properties such as a high fiber content, good shear and compressive performance, and high processing efficiency.

S1320204 一方向炭素繊維強化プラスチックの溝加工([S132-02]先進切削加工技術(2))

When a CFRP (Carbon Fiber Reinforced Plastics) plate, which is light weight and high strength composite material, is machined with a cutting tool, the surface integrity depends on the cutting direction with respect to the fiber orientation. The cutting tests were conducted in planning of unidirectional CFRPs with a single crystal diamond tool at a cutting speed of 100 mm/min in a depth of cut of 75 μm. In this study, "the cutting direction angle" is defined as the relative angle of the cutting direction with respect to the fiber orientation. The cutting forces and the surface finishes are investigated at cutting direction angles of 0, 45 and 90 degrees. The surface is finished without damages in subsurface at a cutting direction angle of 0 degree. Meanwhile, the huge delamination on the surface and the large damages in the subsurface occur with cutting of fibers and pulling of matrix at a cutting direction angle of 90 degrees. The breakage of the fibers and the delamination induce vibrations in the cutting forces at cutting direction angles of 0 and 90 degrees.