Nonlinear Effects in Unidirectional Elastic Memory Composite Material

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.

Near-term and future spacecraft and satellites will require large ultra-lightweight structures and components that must be efficiently packaged for launch and reliably deployed on orbit. A new material technology called Elastic Memory Composite (EMC) materials, shows promise in meeting these needs. The EMC polymer matrix materials enable a fully cured composite structure or component to be deformed or folded for efficient packaging into a spacecraft or launch vehicle, then regain its original shape with no degradation or loss in mechanical or physical properties. A component using EMC materials is fabricated in its deployed, on orbit shape using conventional composite manufacturing processes. Then by heating the material and applying force this fully cued composite material can be folded or deformed for packaging. When cooled, it will retain the packaged shape indefinitely. When reheated the structure will regain its original shape with little or no external force. This packaging/deployment cycle is reversible. This paper reviews new developments in EMC materials technology including material properties, analytical and designs tools, testing and evaluation protocols, and new applications.

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 stress–strain behavior of municipal solid waste (MSW) is important to predicate the deformation of MSW in landfills. Triaxial tests under K 0 consolidation with different stress paths were carried out on MSW samples. Test results of the MSW are compared with that of clays in terms of stress–strain responses and coupled components. In triaxial extension tests, the stress–strain responses of MSW are similar to that of clays reported in literature. In triaxial compression tests, however, the stress–strain responses of the MSW are different from that of the clays, especially a progressively increasing upward curvature is observed at large strains without reaching a peak stress state on the compression stress paths of $$\Delta \sigma_{3}^{{\prime }}$$ ≥ 0. For the stress paths Δq = 0 and Δp′ < 0, although the volume of MSW specimen is expanded, the axial strain is increased, which is different from the behavior of the clays. Compared to the clays, the cross-coupling responses of the MSW are more pronounced. The most variations for shear and bulk modulus of MSW occur in q unloading range and p′ unloading range, respectively. The yield surface of MSW in p′ − q space is obtained and the fibrous reinforcement within specimens is confirmed in this study. Consequently, the stress–strain responses, shear and bulk modulus, and yielding characteristics of MSW are all closely related to the stress path.

In this study, theoretical calculations were performed to determine the most efficient utilization of nanoclays added as reinforcement for CFRP composite materials used for wind turbine blade manufacture. Four different V39 blade models were created, and numerical simulations by FEA were performed. Glass Fibre Reinforced Polymers (GFRP), whole model made of Carbon Fibre Reinforced Polymers/nanoclay (2%) (CFRPN2), Hybrid Glass and Carbon/nanoclay (2%) (HGCN2) and Hybrid Glass and Carbon/nanoclay (5%) (HGCN5). The targeted part was the joining zone between the root and the blade. The most important finding to emerge from this study is that the modest addition of nanoclay (2%) with carbon fiber reinforced polymer leads to a significant stiffer blade, with a minimal deflection, about 70% lower than GFRP. Furthermore, the HGCN2 model is considered to be safer as it has a lower stress concentration than others (52.84 kN/m2). It can be considered that the probability of failure of the entire root area will be decreased if nanoclay-CFRP hybrid blades are used, yielding higher durability and lower overall costs. These findings contribute to decisions related to materials selection, structural, aerodynamic design and layup schedule choice.

Introduction. Existing methods of reinforced concrete structures strengthening are very expensive and time-consuming. The development of new strengthening systems allowing to reduce time and cost of works is perspective and relevant task. Modern methods of strengthening with composite materials are insufficiently studied in Russia. Particularly if the behavior of composite materials in the reinforced concrete structures is concerned. The lack of research in this area leads to the overrun of materials and increase in the cost of structures’ strengthening. The aim of this work is to study the relative deformations of composite materials in the longitudinal and transverse directions during the operation of eccentrically compressed flexible reinforced concrete poles.Materials and methods. The factual basis for the research are the results of experimental studies of the strength and deformability of eccentrically compressed reinforced concrete poles, strengthened with various types of composite external reinforcement. In the most loaded zones of the composite reinforcement, the 2 cm-long strain gauges were glued, capable of detecting changes in relative deformations up to 0.001 mm. In total, the results of operation of 5 poles were used in the analysis. During the experiment, deflections and relative deformations of concrete and composite materials were determined.Results. In the result of experimental studies, relative deformations of composite materials in the longitudinal and transverse directions were obtained. The measurements were carried out at a stepwise increasing load equal to 10 % of the breaking load. Based on the data obtained, graphs of the dependence of the change in relative deformations on the load levels were plotted for each tested sample. In addition to the readings of strain gauges, deflections of tested samples were obtained during testing and graphically presented.Discussion and Conclusions. The obtained experimental data on deflections and relative deformations in composite materials made it possible to determine the zones of the most and least strained sections of the composite reinforcement. Based on the analysis of these data, conclusions were drawn about the development of new strengthening systems that can significantly save the amount of composite materials used without reducing their efficiency.

Building an extraterrestrial research base is the dream of mankind, exploring and utilizing extraterrestrial resources is a frontier topic in space science research. This paper takes the in-situ utilization of extraterrestrial resources and in-situ manufacturing of materials as the starting point, and deeply analyzes the basic situation of extraterrestrial resources and environment. The relationship between the extraterrestrial environment and material composition, organizational structure, molding process, and performance is demonstrated, and its advantages in metal smelting, functional ceramic crystallization, and composite material molding are highlighted. The relevant plans and research status of the international in-situ manufacturing of functional fibers, braids, and composite materials in extraterrestrial space represented by the moon are analyzed, focusing on the application of three types of fibers and their molding materials: structural functions, optics, and metals, and a feasibility plan is proposed. Fibers are the core key from extraterrestrial resources to applications, and braids and composite materials are directly oriented to product objects. The three have important research and engineering significance. Finally, development suggestions are given for the research and application of functional fibers, special braids, and structural and functional integrated composite materials in the field of lunar in-situ manufacturing.

Production of electric power by nuclear power plants (NPP) in the world and in Russia accounts for about 17%. Much attention is currently paid to safe NPP operation and to enhancement of their reliability. Present-day nuclear power plants with high-temperature gas-cooled rectors require development and application of new composite materials capable to withstand high temperatures and mechanical stresses. Ceramic composite materials where whiskers of heat-resistant chemical compounds are used as reinforcement fibers look promising for those purposes. The paper investigates and analyses the opportunity of applying whiskers as reinforcement fibers for heat-resistant composite ceramic building materials. Studies revealed that whiskers of silicon carbide and aluminium nitride are resistant towards high temperature heating without notable change in their chemical composition. It was found out that mono crystals of silicon carbide have higher mechanical strength owing to lack of defects in its structure. Linear heat expansion factors of silicon carbide that are needed for thermo-chemical calculations of composite materials on its base were determined.

ABSTRACTCycloaliphatic epoxies (CEs) are commonly used for structural applications requiring improved resistance to elevated temperatures, UV radiation, and moisture relative to other epoxy materials. Accurate and efficient computational models can greatly facilitate the development of CE‐based composite materials for applications such as Aluminum Conductor Composite Core high‐voltage power lines. In this study, a new multiscale modeling method is developed for CE resins and composite materials to efficiently predict thermal properties (glass‐transition temperature, thermal expansion coefficient, and thermal conductivity). The predictions are compared to experimental data, and the results indicate that the multiscale modeling method can accurately predict thermal properties for CE‐based materials. For 85% crosslink densities, the predicted glass‐transition temperature, thermal expansion coefficient, and thermal conductivity are 279 °C, 109 ppm °C−1, 0.24 W m−1 K−1, respectively. Thus, this multiscale modeling method can be used for the future development of improved CE composite materials for thermal applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46371.

Natural fibers have been used to reinforce materials in many composite structures. Many types of natural fibers have been investigated including flax, hemp, ramie, sisal, abaca, banana etc., due to the advantage that they are light weight, renewable resources and have marketing appeal. These agricultural wastes can also be used to prepare fiber reinforced polymer hybrid composites in various combinations for commercial use. Application of composite materials in structural applications has presented the need for the engineering analysis. The present work focuses on the fabrication of polymer matrix composites by using natural fibers like banana and cotton which are abundant in nature and analysing the effect of mechanical properties of the composites on different surface treatments on the fabric. The effect of various surface treatments (NaOH, SLS, KMnO4) on the mechanical properties namely tensile, flexural and impact was analyzed and are discussed in this project. Analysing the material characteristics of the compression moulded composites; their results were measured on sections of the material to make use of the natural fiber reinforced polymer composite material for automotive seat shell manufacturing.

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.

In this chapter a review on the research of nano-enabled self-sensing structural composite materials is performed. The self-sensing concept is attained by exploiting the intrinsic electrical properties of a structural composite material. Recent research on self-sensing was stimulated by the introduction of nanotechnology in the field of composite materials. Nano-scale fillers such as carbon nanotubes (CNTs), due to their excellent electrical properties, may offer benefits of additional reinforcing phase acting at the nano-scale. The research may be divided into two distinctive categories depending on the type of fibre reinforcement. One category is the research that used electrically non-conductive glass fibre reinforced plastics (GFRP) where carbon nanotubes in various forms are incorporated into the composite to enable sensing. The other category is the research that used electrical conductive carbon fibre reinforced plastics (CFRP) where the carbon nanotubes in various forms are used to enhance the electrical sensing capabilities of the composite.

This special issue of the Journal of Aerospace Engineering contains a collection of invited papers written by experts working in various areas of composite materials and structures. Some of these papers are based on the presentations delivered in the ‘‘Advanced Composite Materials for Civil/Aerospace Engineering Applications’’ session organized by the ASCE Aerospace Division’s Committee on Advanced Composite Materials at the 2001 SDM Conference. The diversity of topics addressed in this special issue deal not only with composite materials and structure, but other fundamental mechanics applications to aircraft/aerospace analysis and design problems. This reflects the broad interests of the committee’s members. The papers address various rapidly growing areas in aerospace/aircraft applications of composite materials and structures, as well as the development of analytical/numerical techniques in support of test methods. The addressed topics include multiscale modeling of composite materials, material parameter estimation for isotropic and anisotropic materials, use of smart materials in vibration damping, development of analysis techniques and test methodologies for impact testing of aircraft engine components and high speed testing of aircraft/aerospace vehicles, and newly emerging lattice structures, as described in more detail later. Bednarcyk and Arnold present a comprehensive multiscale analysis for the response of metal matrix composites and apply it to a particular material system. The analysis combines micromechanical predictions for the individual ply response within the lamination theory analysis at each loading step. The effects of matrix inelasticity and local damage mechanisms such as fiber breakage/debonding and fatigue-induced matrix damage are taken into account. They developed micromechanics-based methodology which is an important step in utilizing the power of micromechanics to predict failure and fatigue life of metal matrix composites. In the paper by Saleeb et al., the writers present a strategy for estimating material parameters using experimental test data and a chosen constitutive material model. The class of admissible constitutive materials includes some recent viscoplastic and damage models. The procedure which consists of three stages, namely analysis, sensitivity and optimization modules, is implemented through a computer program. The method’s effectiveness is demonstrated through the use of specific experimental data, which reflects different observed material behavior. The use of smart sensors and actuators in active vibration damping of composite beams is the topic of the paper by Song et al. The writers present two approaches for active vibration control of laminated composite beams based on positive and strain rate feedback control algorithms. The experiments that demonstrate the utility of these algorithms are supported by analytical and numerical analyses of the beam response. The paper by Roberts et al. is a conceptoriented contribution in which the writers develop a methodology for evaluating different design concepts for aircraft engine fan cases, taking into account potential failure modes due to impact damage. Experimental impact data are supplemented by numerical analyses of impacted composite panels in order to identify appropriate specimen designs and related failure modes, and offer potential solutions to minimizing impact-induced damage. The results indicate that composite materials are viable candidates for use in aircraft engine fan cases when impact is a limiting design parameter. In the paper by Kocher et al., the writers investigate selected failure modes of a new generation of structural components, known as lattice structures, and how such modes impact the design of these structures. These structures consist of sandwich panels reinforced with truss members in the core. Simple analytical approaches are employed to focus on designs that lead to particular failure modes, and these are further investigated using the finite-element method. Both the topic and the generated results complement the current material/structural development efforts for advanced aircraft/aerospace applications. Finally, Baker et al. develop a model and an analysis technique for a practical problem of rail heating of the Air Force’s high-speed test track facility. This model demonstrates the importance of including temperature fields when analyzing the response of rails subjected to impact loading induced by high-velocity vehicles.

Fiber waviness in laminated composite material is introduced during manufacture because of uneven curing, resin shrinkage, or ply buckling caused by bending the composite lay-up into its final shape prior to curing. The resulting waviness has a detrimental effect on mechanical properties, therefore this condition is important to detect and characterize. Ultrasonic characterization methods are difficult to interpret because elastic wave propagation is highly dependent on ply orientation and material stresses. By comparison, the pulsed terahertz response of the composite is shown to provide clear indications of the fiber waviness. Pulsed Terahertz NDE is an electromagnetic inspection method that operates in the frequency range between 300 GHz and 3 THz. Its propagation is influenced by refractive index variations and interfaces. This work applies pulsed Terahertz NDE to the inspection of a thick composite beam with fiber waviness. The sample is a laminated glass composite material approximately 15mm thick with a 90-degree bend. Terahertz response from the planar section, away from the bend, is indicative of a homogeneous material with no major reflections from internal plies, while the multiple reflections at the bend area correspond to the fiber waviness. Results of these measurements are presented for the planar and bend areas.