Developments in elastic memory composite materials for spacecraft deployable structures

Elastic Memory Composite (EMC) materials exhibit many favorable qualities for deployable space structures and have piqued a broad interest within America's deployable space structures industry. EMC materials are similar to traditional fiber-reinforced composites except for the use of a thermoset shape memory resin that enables EMC materials to achieve much higher failure strains than traditional composites when exercised through a very specific thermomechanical load cycle. This unique behavior is exploited in the development of EMC structural components that exhibit very high packaging-strain capability while guaranteeing predictable postdeployment structural performance. This paper presents a review of the current state of development of EMC technologies and EMC deployable space structure components. The paper is intended primarily to help potential users of EMC materials develop a better understanding of the special capabilities of EMC materials and considerations that must be applied while engineering with EMC materials.

Furlable structures are a class of deployable structures that utilize distributed material strain as a means for compact packaging. Elastic Memory Composite (EMC) materials are ideally suited for furlable structures because they offer high strength, stiffness, and strain capacity for efficient packaging and deployed structural performance. EMC components are packaged in their soft-resin state, which enables higher packaging strains than traditional hard-resin composites. For example, packaging strains on the order of 2-5% are commonly achieved in carbon-fiber-reinforced EMC materials whereas non-EMC, carbon-fiber composites are limited to less than 1% strain. The present paper summarizes two recent advancements in the state-of-the-art of EMC materials: 1) improvments to the design of EMC longerons, key structural elements in furlable truss booms, and 2) advancements in analytical models for EMC material behavior through the use of a Multicontinuum Theory. Preliminary results are presented that illustrate the significant potential for these advancements to further improve the performance and capability of furlable EMC space structures.

Elastic memory composite (EMC) materials exhibit many favorable qualities for deployable structures and have piqued a broad interest within America's deployable space structures industry. EMC materials are similar to traditional fiber-reinforced composites except for the use of a thermoset shape memory resin that enables much higher packaging strains than traditional composites without damage to the fibers or the resin. This unique capability is being exploited in the development of very efficient EMC structural components for deployable spacecraft systems. The present paper is intended primarily to help deployable system designers develop a better understanding of the special capabilities of EMC materials, and the unique considerations that must be applied when engineering structural components with these materials. Specifically, the paper discusses: 1) the impacts of incorporating EMC materials on deployable system design, 2) analyses for packaging strain, deployment time, and deployment energy; and 3) requirements and concepts for heating systems.

The growing application of TEMBO Elastic Memory Composite (EMC) materials for deployable space structures has highlighted the need for an improved understanding of the material’s mechanical behavior. Recent mechanical testing has revealed significant nonlinearity in the stress-strain response of highly-aligned, unidirectional EMC materials. It is hypothesized that the nonlinearity in the material’s longitudinal modulus is due to a combination of nonlinear behavior inherent in the carbon fiber reinforcement and processinduced wavy fiber imperfections in EMC laminates. A model is developed accounting for fiber nonlinearity and process-induced wavy fibers and using this model, a data-analysis protocol is developed that allows the relative contribution of these effects to be separated out of the observed global nonlinear stress-strain response. In essence, this protocol provides an indirect method of measuring the effective magnitude of the wavy fiber imperfections, given an accurate knowledge of the nonlinear elastic response of the fibers, or vice-versa. The results for the test laminates considered indicate that the nonlinearity in the fiber reinforcement is predominately responsible for the nonlinear behavior of the composite material. However, effects due to process-induced wavy fibers on the longitudinal modulus can become significant at relatively high compression strains.

At present, the modern society utilizes composite materials in various branches of the national economy. The properties of such materials depend on their composition and structure, and may considerably differ from the properties of source materials. In turn, texture and structure of crystals, their packing order, size and level of sophistication affect the structure of materials. This is particularly demonstrated by hydration curing materials on the basis of gypsum and magnesia binding materials, as well as portland cement. Structuring control is one of the key problems of composite materials. Gypsum binding materials with various modification composition are suggested as a model system to study the influence of texture and structure of materials on their properties. One of them is the construction gypsum – an anhydrite binder and a multiphase gypsum binder (MGB). Scanning electron microscopy (SEM) was chosen as the main method of study. It is found that gypsum crystals that are formed during hydration and curing of gypsum binders with various modification composition have different texture and structure. It prevents from getting the optimal packing of a material. It is justified and confirmed that the MGB consisting of several modifications of calcium sulfate allow choosing the best material composition due to the combination of crystals having different size and form. Besides, MGB contains significant amounts of insoluble anhydrite that reduces the water-gypsum ratio of a binder and compacts its structure. Considerable attention is paid to microfillers, which significantly affect the texture and structure of materials based on gypsum binders. Iron ore concentrate of the Lebedinsky GOK generally consisting of magnetite, as well as impalpable flour cullet waste of sodium and potassium glass were used as microfillers in the given study. Ultra- and nanodispersed powders at their introduction to gypsum and anhydrite compositions change the size and morphology of crystal newgrowths and ensure the formation of ordered, denser and uniform fine-crystalline structures of composite materials, which leads to the reduction of structure imperfection, porosity and increase in contact areas of crystalline hydrates increasing physical and mechanical performance of gypsum materials. Efficient composite construction materials are obtained on the basis of MGB and microfillers.

One considers linearly elastic composite material (CM), which consist of a homogeneous matrix containing a statistically homogeneous random set of aligned homogeneous heterogeneities of non-canonical (i.e. nonellipsoidal) shape. The new general integral equations (GIE) connecting the stress and strain fields in the point being considered with the stress and strain fields in the surrounding points are obtained for the random fields of heterogeneities. The method is based on a recently developed centering procedure where the notion of a perturbator is introduced in terms of boundary interface integrals that makes it possible to reconsider basic concepts of micromechanics such as effective field hypothesis, quasi-crystalline approximation, and the hypothesis of ellipsoidal symmetry. In particular, we used a meshfree method based on fundamental solutions basis functions for a transmission problem in linear elasticity. As a particular problem allowing us to get an exact result, we consider a linear elastic CM, which consists of a homogeneous matrix containing a statistically homogeneous random set of non-canonical inclusions. The elastic properties of the matrix and the inclusions are the same, but the stress-free strains are different. Increasing of volume fraction of inclusions can lead to change of a sign of local residual stresses estimated by either the new approach or the classical one. The main properties of the method are analyzed and illustrated with several numerical simulations in 2D infinite domains containing statistically homogeneous random field of inclusions.

Elastic-memory composites (EMCs) is a class of polymeric composites that can be folded into a very compact shape and later deployed to the original shape upon reheating. They have significant potential in developing large deployable structures greater than 10m in size that can be stowed in a small launch vehicle and deployed in space to predetermined levels of precision. Generally, the composite is folded by heating it above the glass transition temperature of the resin. The primary deformation mode that allows EMCs to achieve significantly higher effective strains than traditional composites is microbuckling of the compressed fibers. The magnitude of this microbuckling dictates whether the laminate behaves elastically or if the laminate exhibits material failure such as fiber breakage, or fiber kinking. This paper explores the micromechanics of both types of fiber-deformation modes associated with the bending of such soft-resin composites. An analysis method is developed and correlated with experimental data to provide an estimate for the level of folding strain that a soft-resin laminate can achieve based on microbuckling-induced material failure. Additionally, insight is provided into the effects of fiber and matrix material properties on the formation and magnitude of the kink mode. Tests were also conducted to determine the deployment accuracy after a number of folding/deployment cycles to help design deployable sensor structures with these materials.

Modern science and technology constantly require new and novel materials with special properties. Over the past decade, Nanocomposites materials have received significant attention as active materials in components ranging from sensors to biomaterials, electronics devices to structural parts. These novel composites have applications in many areas, such as energy, insulation, manufacturing, and the modern building industry. However, not all applications have the same requirements in terms of acoustic insulation, so it is useful to adapt the kind of core materials and their product specifications, such as particle size and porosity, to the different applications. Furthermore, in some applications, cheaper core materials, like precipitated silica, would be a reasonable alternative to replace the time-consuming series of measurements. Because of many bad conditions that affect acoustic insulation properties in modern buildings. And to summarize recent applications of nanotechnology as they relate to textile fibers, yarns, and fabrics for improving acoustic insulation in modern buildings and civilian communities, this paper discusses the ability to apply 3D woven spacer fabric (3DWSF) composite materials reinforced with epoxy, rigid polyurethane foam, and silica nanoporous particles, which were prepared by the sol-gel technique. Four samples had been prepared, all of these samples were textile composite materials, and reinforced with two types of nano silica 99.8% SiO2; mesoporous Ns particles with porosity up to 83%, true density 0.08 g/cm³, and particle size between 100 and 2000 nm and pore size 70–150 nm, which had been prepared by Sol-gel technique, and nonporous Aerosil®200 particles with surface area 200–225 m2/g, true density 0.25 g/cm³, and particle size between 2 and 20 nm. We used rigid polyurethane foam as core material, and epoxy resin for laminating the fabric. 3D spacer E-glass fabrics, and chopped E-glass microfibers had been used. The weight percentage of silica nano particles which were used in this research was 5% by weight, which was better for economic reasons, and enough, to enhance the acoustic absorption coefficient up to [Formula: see text] = 99.79%. The best sound absorption could be achieved by using mesoporous silica nanoparticles, and soundproofing of an insulator using this porous structure is better than using a nonporous one. We found in this research that the thickness 45 mm and semi-porosity structure of the 3DWSF composite insulator material were enough to make a difference, with reference to the thermal and acoustic insulation guide of buildings.

Preface to the Second Edition. Preface to the First Edition. 1. Introduction to Composite Materials. 2. Anisotropic Elasticity and Composite Laminate Theory. 3. Plates and Panels of Composite Materials. 4. Beams, Columns and Rods of Composite Materials. 5. Composite Material Shells. 6. Energy Methods For Composite Material Structures. 7. Strength and Failure Theories. 8. Joining of Composite Material Structures. 9. Introduction to Composite Design. Appendices: A-1. Micromechanics. A-2. Test Standards for Polymer Matrix Composites. A-3. Properties of Various Polymer Composites. Author Index. Subject Index.

Addressing the current lining cracking problem in coastal tunnels, this paper independently introduces a novel type of repair material for tunnel lining cracks—the composite repair material consisting of waterborne epoxy resin and ultrafine cement (referred to as EC composite repair material). Through indoor testing, we have analyzed the change rule of the mass change rate, compressive strength, flexural strength, and chloride ion concentration of the repair material samples in erosive environments, with the dosage of each component in the EC composite repair material being varied. We have also investigated the working performance, mechanical properties, and microstructure of the repair material. The results of this study show that when the proportion of each component of ultrafine cement, waterborne epoxy resin, waterborne epoxy curing agent, waterborne polyurethane, defoamer, and water is 100:50:50:2.5:0.5:30, the performance of the EC composite repair material in a chloride ion-rich environment is optimal in all aspects. When the mixing ratio of each component of the EC composite repair material is as stated above, the repair material exhibits the best performance in a chloride ion erosion environment. With this ratio of components in the EC composite repair material, the fluidity, setting time, compressive strength, flexural strength, and bond strength of the repair material in a chloride ion erosion environment can meet the requirements of relevant specifications, and it is highly effective in repairing tunnel lining cracks. The polymeric film formed by the reaction between the waterborne epoxy resin emulsion and the curing agent fills the pores between the hydration products, resulting in a densely packed internal structure of EC composite repair material with enhanced erosion resistance, making it very suitable for repairing cracks in tunnel linings in erosive environments.

The effect of elevated and lowered temperatures on the elastic properties of carbon fiber-epoxy composite material was studied using multi-phase unit cell (MPUC) numerical model. Evaluation of the elastic properties of carbon fiber-epoxy composite material is based on the finite element method. Obtained results confirmed that elevated and lowered temperature has noticeable influence on elastic properties of carbon fiber-epoxy composite material. As demonstrated, this fact has considerable influence on accurate evaluation of generated thermal stresses in real laminated composite structures, exposed to extremely high or low operating temperatures.

The main challenging issues of vehicles with electric propulsion are on the limited energy source due to relatively low battery capacity and low excitation of power traction. They can be tackled down by designing lightweight structures for frameworks and bodies of the vehicles. Composite materials which have a high strength to weight ratio are the best choice for designing and manufacturing the lightweight structures. A review of recent progress in utilization of the composite materials for electric vehicle structures is presented. It focuses on how the structures can support the electric vehicles to compete with internal combustion engine vehicles regarding their performance on the road. The utilization of composite material for structures of railway vehicles is also summarized. Furthermore, discussions are extended to the key technologies required for applying the composite materials in Indonesia such as composite–metal joint technology, fiber and matrix production technology, and numerical analysis competency for modeling the composite.

Nondestructive evaluation of interfacial damages in composite materials

The results of investigating the influence of processing methods on the structure and properties of composite polymeric materials are given. It has been established that the defectiveness of the structure of highly filled composite polymeric materials is closely tied with the inhomogeneity of the molecular weight characteristics of the polymer and with the non-uniformity of distribution of the filler particles in morphological zones of the article, and may be attributed to the difference in the moulding conditions of the material in the mould cross-section.

With the increasing applications of composite materials in various engineering structures, failure analysis on crack induced fracture problems in composite materials has attracted more and more attention among researchers. In the current work, with the plastic zone corrections, the elastic-plastic fracture behavior investigations on crack problems in different configurations have been carried out. Two approaches of plastic zone correction are demonstrated. The first one is the mixed-mode Dugdale model for interface cracks and the second one is the generalized Irwin model which is suitable for matrix cracking. The introduction of plastic zone can greatly improve the accuracy of fracture prediction in fiber-reinforced composite materials with ductile matrix. Based on the two models, the problem of a crack lying at the interface of two semi-infinite plate, and crack-coated inclusion interactions have been studied. Numerical examples are given to show the influence of different kinds of parameters on the plastic zone size and crack tip opening displacement of each problems. Some useful conclusions have been figured out after the investigation.