Lightweight Composite Materials Research Articles

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.

우주용 일체형 경량 복합재료 전자장비 하우징 제작에 관한 연구

기존 위성 전자장비 하우징에 널리 사용되는 알루미늄 합금 소재를 경량 복합재료로 대체함으로써 위성 경량화를 크게 개선하고자, 경량 복합재료로 구성된 전자장비 하우징을 제작하고 성능 검증에 대하여 다루었다. 이를 위해 복합재료의 낮은 가공성을 극복하기 위하여 후처리를 최소화할 수 있는 복합재료 하우징 제작공정을 설계하고, 격자 구조로 강화된 일체형 하우징 본체를 동시경화 방법에 의해 제작하였다. 또한 제작된 전자장비 하우징의 내구성, 강성, 열전도도, 전기전도도, EMI차폐 및 방사차폐에 대한 성능 평가 결과를 분석하였다. 아울러 본 연구에서 제작한 복합재료 하우징은, 동일한 형상의 알루미늄 하우징 대비 상당한 질량절감을 가능하게 함을 제시하였다. This paper dealt with the fabrication and performance evaluation of the electronics housing made of lightweight composite materials, aiming at the enhancement of satellite mass savings by replacing conventional aluminum alloy widely used for satellite avionics with lightweight composite material. For this purpose, a fabrication process was designed to overcome low machinability of CFRP and to minimize the post-treatment. The composite housing with grid-stiffened and monolithic frame was made using co-curing method. Its performance was also evaluated regarding endurance, stiffness, thermal conductivity, electrical grounding, EMI protection and radiation shielding. The composite housing can provide the considerable mass savings over the aluminum housing with same dimension.

Trial Manufacture of Bionic Honeycomb Plates and their Bending Properties

In order to develop the lightweight composite materials, we developed an integrated manufacturing method. The first trial production of the integrated honeycomb plate was fairly rough. This paper focuses on the trial manufacture of bionic honeycomb plates and discusses their mechanical properties. The conclusions were :1) An edge-sealing bionic integrated honeycomb plate has been provided; 2) some specific cases of improving the integrated manufacturing technology have been studied; and 3) the failure strength in the integrated honeycomb plate is significantly higher than that of the honeycomb plate with the adhesive layer.

Model and Fabrication of Biomimetic Integrated Porous Core Laminated Composite

This paper deals with imitating a novel type of biomimetic integrated composite with porous core layer from the beetle elytra microstructures. Firstly,the microstructures of the elytron of Anoplophora Glabripennis, Anomala Corpulenta Motschulsky, Prosopocoilus Inclinatus and Melolonthidae were examined with SEM. Inspired by these structure characteristics, a biomimetic composite model was proposed, in which the two face layers were interconnected with a porous core layer, and there are continuous fibers embedded into these three layers to enhance mechanical performance of the laminated composite. Then a specimen of this laminated composite with porous core layer was made. The procedures include: weaving a piece of two layers space fabric by glass fibers as the preform of the composite,filling the mixed resin which contained 50% granular paraffin wax and 50% epoxy resin into the space of the fabric, putting it into a flat mold, keeping 36 hours, and finally heating the composite to remove the paraffin wax to form the porous core layer. The experiment showed that the model of integrated porous core laminated composite inspired by the beetle elytra structure is reasonable and this novel type of lightweight composite material was manufacturable.

Core–Shell–Corona Polymeric Micelles as a Versatile Template for Synthesis of Inorganic Hollow Nanospheres

Hollow, inorganic nanoscale capsules have many applications, from the delivery of encapsulated products for cosmetic and medicinal purposes to use as lightweight composite materials. Early methods for producing inorganic hollow nanospheres using hard templates suffered from low product yield and shell weakness upon template removal. In the past decade, researchers have turned to amphiphilic copolymers to synthesize hollow nanostructures and ordered mesoporous materials. Amphiphilic molecules self-assemble into well-defined nanostructures including spherical micelles. Micelles formed from simple, two-component AB diblock and ABA triblock copolymers, however, have been difficult to work with to construct inorganic hollow nanoparticles, because the corona of the micelle, which serves as the template for the shell, becomes unstable as it absorbs inorganic shell precursors, causing aggregates to form. Newly developed, three-component ABC triblock copolymers may solve this problem. They provide nanoassemblies with more diverse morphological and functional features than AB diblock and ABA triblock copolymers. Micelles formed from ABC triblock copolymers in selective solvents that dissolve only one or two of the blocks provide templates for these improved nanoassemblies. By manipulating individual polymer blocks, one can "encode" additional features at the molecular level. For instance, modifying the functional groups or substitution patterns of the blocks allows better morphological and size control. Insights into polymer self-assembly gained over years of work in our group have set the stage to systematically engineer inorganic spherical hollow nanoparticles using ABC triblock copolymers. In this Account, we report our recent progress in producing diverse, inorganic hollow spherical nanospheres from asymmetric triblock copolymeric micelles with core-shell-corona architecture as templates. We discuss three classes of polymeric micelles-with neutral, cationic, and anionic shell structures-that allow fabrication of a variety of hollow nanoparticles. Importantly, we synthesized all of these particles in water, avoiding use of hazardous organic solvents. We have designed the precursor of the inorganic material to be selectively sorbed into the shell domain, leaving the corona free from the inorganic precursors that would destabilize the micelle. The core, meanwhile, is the template for the formation of the hollow void. By rationally tailoring experimental parameters, we readily and selectively obtained a variety of hollow nanoparticles including silica, hybrid silicas, metal-oxides, metal-carbonates, metal-sulfates, metal-borates, and metal-phosphates. Finally, we highlight the state-of-the-art techniques we used to characterize these nanoparticles, and describe experiments that demonstrate the potential of these hollow particles in drug delivery, and as anode and cathode materials for lithium-ion batteries.

High Mechanical Performance of Layered Graphene Oxide/Poly(vinyl alcohol) Nanocomposite Films

The design and fabrication of strong, lightweight, and damage-resistant composite materials are major topics of studies on composites. Biomimetics, a developing multidisciplinary field, is now leading the fabrication of novel materials with remarkable mechanical properties. Graphene oxide (GO), a graphene derivative, possesses good mechanical properties, a high aspect ratio, and good solubility in aqueous solutions, indicating great potential in nanocomposite fields. In this work, bioinspired layered GO/poly(vinyl alcohol) (PVA) nanocomposite films with remarkable mechanical performances are prepared by an environmental friendly, bottom-up assembly methodology. The structural analysis shows alternate piles of inorganic GO platelets and organic PVA binder. Tensile tests indicate that the borate-treated GO/PVA nanocomposite films display 360 MPa of strength, which is twofold to threefold higher than that of biological materials (e.g., nacre). Toughness of GO/PVA nanocomposites is also enhanced fourfold compared with nacre. To reveal the toughening function of the intercalated polymer in the nanocomposites, the influence of polymer with varied molecular weights (Mws) on the fracture mode of the nanocomposites is systematically investigated through quasi-static tensile and creep tests. The PVA molecules with a higher Mw can connect more neighboring GO platelets through inter- and intra-linkages than those with a lower Mw, resulting in efficient stress transfer along the GO plane direction. Thus, tensile strength and toughness are improved. This work illustrates the functions of bonding types between inorganic-organic phases and intercalated polymers with different Mws on the mechanical properties of the layered nanocomposites, including stiffness, strength, and toughness.

Carbon Nanotubes and Their Applications,

The carbon nanotubes are expected to have a wide variety of interesting electrical and mechanical properties. For the potential applications of nanoelectronics, carbon nanotubes are ranged from fabricating individual transistor devices at nanometer scale to wiring in integrated circuits. Their high stiffness, coupled with their low density, implies that carbon nanotubes might be useful as nanoscale fibers in ultrastrong, lightweight composite materials. In this article, we introduce the recent approach of carbon nanotubes and discuss their future of applications.

초기 균열길이 및 섬유방향이 CFRP/GFRP 하이브리드 적층재의 층간 파괴에 미치는 영향

Considering the wind power system and the rotor blades which are composed of much technology, the wind power blade would be the most dangerous part because it revolves at high speed and weighs about dozens of tons, if the accident happens. Therefore, the light weight composite materials have been replacing as substitutional materials. The object of this study is to examine the delamination and damage for CFRP/GFRP hybrid composite that is used for strength improvement of a wind power blade. The influence of the initial crack length and fiber orientation for the interlaminar delamination was exposed for the blade safety. Plain woven CFRP instead of GFRP was inserted into the layer of the box spar for improving the strength and blade life. DCB(Double Cantilever Beam) specimen was used for evaluating fracture toughness and damage evaluation of interlaminar delamination. The material used in the experiment is a commercial material known as CF 3327 EPC in plain woven carbon prepreg(Hankuk Carbon Co.) and UD glass fiber prepreg(Hyundai Fiber Co.). From the results, crack growth rate is not so different according to the variation of the initial crack length. Mode I interlamainar fracture toughness of fiber direction <TEX>$0^{\circ}$</TEX> is higher than that of <TEX>$45^{\circ}$</TEX>. Interlaminar fracture has an effect on fiber direction and K decreased with lower value according to increasing initial crack length. Also energy release rate fracture toughness was evaluated because CFRP/GFRP hybrid composite with a different thickness is under the mixed mode loading condition. The interlaminar fracture was almost governed by mode I fracture even though the mixed mode.

Synthesis and Characterization of Antimony Doped Tin Oxide Nanocomposites for Li-Ion Batteries

Carbon nanotubes (CNTs) have been suggested as a substitute for the graphite anode in lithium-ion batteries. Their unique one-dimensional tubular structure, high electrical conductivity, and large surface area [1 6] are promising features for highly e cient Li storage. However, two disadvantages are inherent in a CNT anode: low volumetric capacity owing to the presence of a large internal void, which is of no use for Li storage [2], and a speci c capacity that is limited by the theoretical maximum capacity of the graphite structure (372 mAh g−1). Antimony dopped tin oxide (ATO) thin lms and microspheres/nanoparticles, in particular, have also been reported as anode materials for lithium-ion battery. The Sb doping was found to increase the electrical conductivity and mechanical stability of the anode, thereby leading to improved electrochemical properties. Mats or so-called buckypapers that contain high concentrations of carbon nanotubes have the potential to form strong and light weight composite materials. CNT-skeleton based composites can solve so many problems faced by bulk electrode materials in Li-ion systems. The structure of the product was characterized by X-ray di raction (XRD, Rigaku D/max 2200 system with thin lm attachment). In this study, CNTs-Sb:SnO2 nanocomposite structures are presented, which integrate both electronic conductivity and bu ering matrix design strategies. The CNTs-Sb:SnO2 nanostructured electrodes have been prepared and applied as anode materials for lithium-ion batteries, which exhibit higher lithium storage capacities and better cycling performance compared to single CNTs and SnO2 electrodes.

Polymeric Composite Foams With Properties Controlled by the Magnetic Field

Polymeric foams with embedded magnetic particles is a new class of lightweight systems that could lead to relevant industrial applications both for their enhanced directional passive mechanical properties and for their sensitivity to magnetic field that can be used to control the mechanical behavior. This paper is aimed to present the magnetomechanical properties of this novel class of functionalized lightweight composite materials, based on polymeric matrices and with suitable distributions of magnetosensitive micro-sized particles. The result of the ad hoc magnetic field application during the foaming process is a tailored degree of both structural and functional anisotropy without affecting the morphology of the cells, and the optimization of the reinforcing efficiency along one direction. The induced particle distribution can be then utilized for a real-time control of structural and functional properties under working conditions.

An indirect hybrid sound transmission loss controller

The control of sound transmission through panels is an important noise control problem in the aerospace, aeronautical, and automotive industries. The trend towards using lightweight composite materials that have lower sound insulation performance is a negative factor regarding low frequency transmission loss. Double-panel partitions with the gap filled with sound absorption materials are often employed to improve the sound insulation performance with reduced added weight penalty. However, in the low frequency range, the strong coupling between the panels through the air cavity and mechanical paths may greatly reduce the sound transmission performance, making it even lower than the performance of a single panel in some frequency ranges. In this work, an experimental investigation of a new kind of hybrid (active/passive) acoustic actuator is presented. The idea consists of replacing the acoustic absorption material by a hybrid actuator aiming at improving the transmission loss at low frequencies without altering the passive attenuation. A prototype of the system is tested in a plane wave acoustic tube setup. Different kinds of SISO feedforward control implementations were used to attenuate the sound power transmitted through the hybrid active–passive panel using an error microphone or a particle velocity sensor placed downstream with respect to the sample panel. Measurement results of the transmission loss with active and hybrid attenuation are presented and discussed.

Modelling the three-dimensional vibration of composite archery arrows under free–free boundary conditions

Archery performance has been shown to be dependent on the resonance frequencies and operational deflection shape of the arrows. This vibrational behaviour is influenced by the design and material of the arrow and the presence of damage in the arrow structure. In recent years arrow design has progressed to use lightweight and stiff composite materials. This paper investigates the vibration of composite archery arrows through a finite difference model based on Euler–Bernoulli theory, and a three-dimensional finite element modal analysis. Results from the numerical simulations are compared to experimental measurements using a Polytec scanning laser Doppler vibrometer (PSV-400). The experiments use an acoustically coupled vibration actuator to excite the composite arrow with free–free boundary conditions. Evaluation of the vibrational behaviour shows good agreement between the theoretical models and the experiments.

Polymer/carbon nanocomposites for enhanced thermal transport properties – carbon nanotubes versus graphene sheets as nanoscale fillers

Light-weight composite materials of superior thermal transport properties are important to thermal management and other applications. Carbon nanomaterials with their high thermal conductivities have been widely pursued for such a purpose. Specifically, carbon nanotubes have been shown both theoretically and experimentally to possess extraordinarily high thermal conductivities at the individual nanotube level, and thus are logically considered as ideal fillers for highly thermally conductive polymeric nanocomposites. However, the predicted dramatically enhanced thermal transport in polymers upon the incorporation of carbon nanotubes has not yet materialized. Recently, graphene research has brought new opportunities to the development of polymer/carbon nanocomposites of high thermal conductivities, with already some successful uses of exfoliated graphite sheets as nanoscale fillers. In this work poly(vinyl alcohol) (PVA) was selected as the polymer matrix for the dispersion of single-walled carbon nanotubes (seamlessly with PVA functionalization and solubilization) vs. few-layer graphene sheets as nanoscale carbon fillers for a more direct comparison on the thermal transport performance in the resulting nanocomposites. The effect of aligning the nanotubes embedded in the nanocomposite films via mechanical stretching was also evaluated. Implications of the comparison between the nanotubes and nanosheets with respect to their potentials in thermally conductive polymeric nanocomposites are discussed.

Nanocelluloses and their use in composite materials

large interest, not only in the academic research society but also in industries, during the last few years. The number of published papers on this topic has increased from some few publications per year in 2005 to more than 500 in 2011. The research topics have been extraction methods of nanocelluloses, their properties, chemical modifications, self-assembling and their use in composites. It is obvious that the world’s largest forest companies believe that nanocelluloses will lead to new uses of forest resources and open a new business area. The uses are expected to be new lightweight composite materials to be used in transport, electronic applications but nanocelluloses can also be used in food, cosmetics, medical, packaging and many other applications. The extracted nanofibres are usually around 20– 30 nm in diameter and the length is estimated to be in !m range while the nanocrystals are much smaller, being about 3–5 nm in diameter and 200 nm in length. The properties of the cellulosic nanomaterials from natural resources (wood, bioresidues, annual plants) have shown to be very similar independent of the original source, meaning that the size distribution of nanofibres is an important factor and that it can be tailored for different applications. The main challenge, when producing cellulose-based nanocomposites, is to disperse the nanoreinforcements in the polymer matrix without degradation of the polymer or the reinforcing phase. Therefore the most common way to prepare cellulose nanocomposites has been the impregnation of ‘cellulose nano paper’ by a polymer resin or use of solvents to disperse the nanocelluloses in a solved polymer. These methods show that composites with high mechanical properties can be prepared but are restricted to thin sheets or films and also small scale process. To produce the nanocomposites in larger scale and with possibility to make different shapes, melt processing technologies need to be developed and that is a challenge because nanofibres and crystals are strongly hydrophilic and when dried it is very difficult to re-disperse them. We know that different chemical modifications, to make them re-dispersible, are usually affecting their thermal stability and crystallinity negatively and there by decreasing the composites properties. Now after some years intensive research, we can see several initiatives, which are taken to produce nanocellulose in large scale, and we are also waiting for the first commercial applications based on these materials. My opinion is that that the first applications will not be composites but barrier coatings on board or paper for packaging applications, stronger paper, and transparent films for electronic applications, medical scaffolds and also nanoporous selective membranes. To be able to develop composites based on nanocellulose we have to solve the dispersion problem as well as to develop suitable processing technologies for large scale.