A nonlinear analytical model of composite plate structure with an MRE function layer considering internal magnetic and temperature fields

To better exert the vibration suppression effect of magnetorheological elastomer (MRE) embedded into a composite structure with structural and functional integration advantage, this study proposes a nonlinear analytical model of such composite plate with an MRE function (MREF) layer, accounting for internal magnetic and temperature fields for the first time. Initially, a 9-layer fiber metal laminated (FML) plate with the MREF composites, consisting of two layers of metal protective skins, two layers of fiber-reinforced polymer (FRP) and one layer of MREF, is taken as an example to describe such a modelling method. Nonlinear expressions of elastic moduli of MRE and FRP involving thermal and magnetic fitting coefficients are also proposed, followed by derivation of the energy expressions of the constituent layers by the Rayleigh-Ritz method. After the free and forced vibrations are solved, the identification procedure of fitting coefficients is described and some literature results are employed to preliminarily validate this model without consideration of internal magnetic field or temperature field or both. Finally, dynamic experiments under different magnetic and temperature conditions are undertaken. The detailed comparison of the natural frequencies and resonant responses are conducted to provide a solid validation of the model developed. It has been found that enlarging the magnetic and temperature fields both facilitate the improvement of the anti-vibration performance. Also, by further increasing the shear modulus of MRE, the volume fraction of carbonyl iron particles or the thickness ratio of the MRE layer to the overall structure, a better vibration suppression capability can be obtained

Finite element analysis of natural fibers composites: A review

Natural fiber composites (NFCs) also termed as biocomposites offer an alternative to the existing synthetic fiber composites, due to their advantages such as abundance in nature, relatively low cost, lightweight, high strength-to-weight ratio, and most importantly their environmental aspects such as biodegradability, renewability, recyclability, and sustainability. Researchers are investigating in depth the properties of NFC to identify their reliability and accessibility for being involved in aircrafts, automotive, marine, sports’ equipment, and other engineering fields. Modeling and simulation (M&S) of NFCs is a valuable method that contributes in enhancing the design and performance of natural fibers composite. Recently many researchers have applied finite element analysis to analyze NFCs’ characteristics. This article aims to present a comprehensive review on recent developments in M&S of NFCs through classifying the research according to the analysis type, NFC type, model type, simulation platform and parameters, and research outcomes, shedding the light on the main applicable theories and methods in this area, aiming to let more experts know the current research status and also provide some guidance for relevant researches

Simultaneous vibration suppression and energy harvesting of vehicle suspension systems: status and prospects

Suspension is one of key components in vehicles, which has the dual functions of load bearing and vibration suppression. As for traditional suspension systems, viscous liquid or dry friction damper is always used to convert vibration energy into heat which is dissipated to achieve vibration reduction. In this case, electric energy is wasted, which is especially unfavorable for newenergy vehicles. In the past decade, novel suspension systems that can both suppress vibration and harvest electrical energy have received high attention and extensive research. In order to comprehensively know the latest progress in synchronous vibration suppression and energy harvesting (SVSEH) of vehicle suspensions, this paper reviews the development history of vehiclesuspensions and summarizes the potential energy that can be collected from road excitations by vehicle suspensions. Then the research status on energy-regenerative suspensions is focused on. In the end, current technical challenges of SVSEH of vehicle suspensions are presented and future directions are discussed. The contribution of this paper is to help domestic researchers toquickly and accurately grasp current status of this field and provide important ideas for the development of new vehicle suspensions

Graphene and CNT impact on heat transfer response of nanocomposite cylinders

Reinforcing polymers with nanofillers is an advanced approach to improve and manage the thermal behaviors of polymeric nanocomposite materials. Among the proposed nanofillers, graphene and carbon nanotube (CNT) with superior thermal conductivity are two advanced nanofillers, which have extensively been utilized to enhance the heat transfer responses of host polymeric materials. In this work, the impacts of randomly oriented graphene and CNT to steady state and transient heat transfer behaviors of functionally graded (FG) nanocomposite cylinders have been investigated using an axisymmetric model. Nanocomposite cylinders have been assumed to be under heat fluxes, heat convections or temperatures as different types of thermal boundary conditions. The thermal properties of the resulted nanocomposite materials are estimated by micromechanical model. Moreover, the governing thermal equations of axisymmetric cylinders have been analyzed using a highly consistent and reliable developed mesh-free method. This numerical method predicts temperature fields via MLS shape functions and imposes essential boundary conditions with transformation approach. The effects of nanofiller content and distribution as well as thermal boundary conditions on the heat transfer responses of nanocomposite cylinders are studied. The results indicated that the use of nanofiller resulted in shorter stationary times and higher temperature gradients in FG nanocomposite cylinders. Moreover, the use of graphene in nanocomposites had stronger impact on thermal response than CNT.The work described in this paper was supported by National Natural Science Foundation of China (Grant no. 11972204) and Natural Sciences and Engineering Research Council of Canada (NSERC under grant RGPIN-217525). The authors are grateful for their supports

Recent Developments in Luffa Natural Fiber Composites: Review

Natural fiber composites (NFCs) are an evolving area in polymer sciences. Fibers extracted from natural sources hold a wide set of advantages such as negligible cost, significant mechanical characteristics, low density, high strength-to-weight ratio, environmental friendliness, recyclability, etc. Luffa cylindrica, also termed luffa gourd or luffa sponge, is a natural fiber that has a solid potential to replace synthetic fibers in composite materials in diverse applications like vibration isolation, sound absorption, packaging, etc. Recently, many researches have involved luffa fibers as a reinforcement in the development of NFC, aiming to investigate their performance in selected matrices as well as the behavior of the end NFC. This paper presents a review on recent developments in luffa natural fiber composites. Physical, morphological, mechanical, thermal, electrical, and acoustic properties of luffa NFCs are investigated, categorized, and compared, taking into consideration selected matrices as well as the size, volume fraction, and treatments of fibers. Although luffa natural fiber composites have revealed promising properties, the addition of these natural fibers increases water absorption. Moreover, chemical treatments with different agents such as sodium hydroxide (NaOH) and benzoyl can remarkably enhance the surface area of luffa fibers, remove undesirable impurities, and reduce water uptake, thereby improving their overall characteristics. Hybridization of luffa NFC with other natural or synthetic fibers, e.g., glass, carbon, ceramic, flax, jute, etc., can enhance the properties of the end composite material. However, luffa fibers have exhibited a profuse compatibility with epoxy matrix

Similitude for the Dynamic Characteristics of Dual-Rotor System with Bolted Joints

The dual-rotor system has been widely used in aero-engines and has the characteristics of large axial size, the interaction between the high-pressure rotor and low-pressure rotor, and stiffness nonlinearity of bolted joints. However, the testing of a full-scale dual-rotor system is expensive and time-consuming. In this paper, the scaling relationships for the dual-rotor system with bolted joints are proposed for predicting the responses of full-scale structure, which are developed by generalized and fundamental equations of substructures (shaft, disk, and bolted joints). Different materials between prototype and model are considered in the derived scaling relationships. Moreover, the effects of bolted joints on the dual-rotor system are analyzed to demonstrate the necessity for considering bolted joints in the similitude procedure. Furthermore, the dynamic characteristics for different working conditions (low-pressure rotor excitation, high-pressure rotor excitation, two frequency excitations, and counter-rotation) are predicted by the scaled model made of a relatively cheap material. The results show that the critical speeds, vibration responses, and frequency components can be predicted with good accuracy, even though the scaled model is made of different materials

Similitude for the Dynamic Characteristics of Dual-Rotor System with Bolted Joints

The dual-rotor system has been widely used in aero-engines and has the characteristics of large axial size, the interaction between the high-pressure rotor and low-pressure rotor, and stiffness nonlinearity of bolted joints. However, the testing of a full-scale dual-rotor system is expensive and time-consuming. In this paper, the scaling relationships for the dual-rotor system with bolted joints are proposed for predicting the responses of full-scale structure, which are developed by generalized and fundamental equations of substructures (shaft, disk, and bolted joints). Different materials between prototype and model are considered in the derived scaling relationships. Moreover, the effects of bolted joints on the dual-rotor system are analyzed to demonstrate the necessity for considering bolted joints in the similitude procedure. Furthermore, the dynamic characteristics for different working conditions (low-pressure rotor excitation, high-pressure rotor excitation, two frequency excitations, and counter-rotation) are predicted by the scaled model made of a relatively cheap material. The results show that the critical speeds, vibration responses, and frequency components can be predicted with good accuracy, even though the scaled model is made of different materials

Storage, patterns, and control of soil organic carbon and nitrogen in the northeastern margin of the Qinghai–Tibetan Plateau

This study tested the hypothesis that soil organic carbon (SOC) and total nitrogen (TN) spatial distributions show clear relationships with soil properties and vegetation composition as well as climatic conditions. Further, this study aimed to find the corresponding controlling parameters of SOC and TN storage in high-altitude ecosystems. The study was based on soil, vegetation and climate data from 42 soil pits taken from 14 plots. The plots were investigated during the summers of 2009 and 2010 at the northeastern margin of the Qinghai–Tibetan Plateau. Relationships of SOC density with soil moisture, soil texture, biomass and climatic variables were analyzed. Further, storage and vertical patterns of SOC and TN of seven representative vegetation types were estimated. The results show that significant relationships of SOC density with belowground biomass (BGB) and soil moisture (SM) can be observed. BGB and SM may be the dominant factors influencing SOC density in the topsoil of the study area. The average densities of SOC and TN at a depth of 1 m were about 7.72 kg C m ^−2 and 0.93 kg N m ^−2 . Both SOC and TN densities were concentrated in the topsoil (0–20 cm) and fell exponentially as soil depth increased. Additionally, the four typical vegetation types located in the northwest of the study area were selected to examine the relationship between SOC and environmental factors (temperature and precipitation). The results indicate that SOC density has a negative relationship with temperature and a positive relationship with precipitation diminishing with soil depth. It was concluded that SOC was concentrated in the topsoil, and that SOC density correlates well with BGB. SOC was predominantly influenced by SM, and to a much lower extent by temperature and precipitation. This study provided a new insight in understanding the control of SOC and TN density in the northeastern margin of the Qinghai–Tibetan Plateau