Dynamic Mechanical Performance Research Articles

Textile structural composites for automotive leaf spring application

This work dealt with the textile structural reinforced composites (TSRC) prepared by different textile structures as reinforcement in epoxy by employing vacuum assisted resin infusion molding (VARIM) process. The textile structures were used in form E−glass uni-directional (UD) tow, bi-directional (2D) plain woven fabric and 3D woven orthogonal fabric. Chopped fibers reinforced composite were also prepared to compare their performance with TSRC. All composite structures were prepared with similar volume fraction and identical processing condition. In this context influence of reinforcement architecture on the static and dynamic mechanical performance of composites were investigated for their applicability in automotive leaf spring compared to conventional steel. TSRC were analyzed for mechanical properties like tensile strength, flexural strength (3 point bending), Izod impact strength. Further damping and wear behavior were also investigated to know their applicability as leaf spring material. Mechanical performance of 3D woven based composite leaf spring were found significantly better than chopped, UD and 2D counterparts with regard to delamination, impact strength and improved storage modulus. Overall 3D composite leaf spring showed high potential for automotive leaf spring applications.

Conductive polysaccharides-based proton-exchange membranes for fuel cell applications: The case of bacterial cellulose and fucoidan

Conductive natural-based separators for application in polymer electrolyte fuel cells (PEFCs) were fabricated by combining a bacterial polysaccharide, i.e. bacterial cellulose (BC), and an algae sulphated polysaccharide, i.e. fucoidan (Fuc). The diffusion of fucoidan aqueous solution containing a natural-based cross-linker, viz. tannic acid, into the wet BC nanofibrous three-dimensional network, followed by thermal cross-linking, originated fully bio-based proton exchange membranes (PEMs). The PEMs present thermal-oxidative stability in the range of 180–200 °C and good dynamic mechanical performance (storage modulus ≥ 460 MPa). Additionally, the BC/Fuc membranes exhibit protonic conductivity that increases with increasing relative humidity (RH), which is a typical feature for numerous water-mediated proton conductors. The traditional Arrhenius-type plots demonstrate a linear behaviour with a maximum protonic conductivity of 1.6 mS cm−1 at 94 °C and 98 % RH. The results showed that these fully bio-based conductive membranes have potential as eco-friendly alternatives to other PEMs for application in PEFCs.

Feasibility of ramie fibers as raw material for the isolation of nanofibrillated cellulose

In this study, a strategy was adopted to enhance the use of ramie fibers as raw material for isolation of cellulose nanofibers (CNFs). Ramie pulp was produced by alkaline organosolv followed by bleaching. CNFs were produced by mechanical defibrillation, and films were fabricated via casting. Effects of number of passes in the mechanical grinding on physical and mechanical properties of CNF films were comprehensively studied. Potential of ramie fibers was proved by fabricating homogeneous nanofibers with average thickness of 8.72 nm, which led to CNF films with dense and non-porous networks, and crystallinity index of 76–78%. Tensile strength (42−82 MPa) and dynamic mechanical (9−11 GPa) performance were good only for less severe mechanical defibrillation. Lower solubility (1.85–2.43%). and activity (0.69) in water, and outstanding barrier properties against water vapor and oxygen make ramie suitable for more sustainable extraction of cellulose nanofibers and production of CNF films for diverse applications.

Static and Dynamic Mechanical Performance of Carbon Fiber Reinforced Polyethersulfone Composites

This study has been carried out to demonstrate the effect of short carbon fiber (SCF) loading on static and dynamic mechanical performance of polyethersulfone (PES) composites. Different combinations of SCF/PES composites were prepared by extrusion followed by injection molding. The static mechanical properties such as hardness, tensile and flexural properties of PES based composites were analyzed following ISO standards. As engineering materials, the polymer composites with high modulus as well as excellent damping properties are of great interest in aerospace and automotive industries for severe dynamic environment. Furthermore, in addition to static properties of composites, dynamic mechanical behaviour of PES based composites was evaluated. Mechanical test results showed that increasing the SCF wt. % in the composites increases the hardness, tensile and flexural properties. Furthermore, the optimal SCF loading was found to be 30 wt. % for significantly improving the overall composite mechanical performance. Upon the reinforcing of SCFs, an improvement in the storage modulus was found. Based on the fractographic analysis, orientation and aligned structure of carbon fibers, good bonding of fibers within the matrix and better fiber-matrix interaction were the primary reasons leading to the improvement of mechanical properties. The optimized composite (PES with 30 wt. % of SCF) could be used in automotive components like frames, flap covers and gears of printing machinery.

MAGNETORHEOLOGICAL ELASTOMER COMPOSITES BASED ON INDUSTRIAL WASTE NICKEL ZINC FERRITE AND NATURAL RUBBER

ABSTRACT Magnetorheological elastomers (MREs) based on waste nickel zinc ferrite and natural rubber were prepared. The amount of waste nickel zinc ferrite was varied at five levels (20, 40, 60, 80, and 100 phr) to assess the optimum amount of waste nickel zinc ferrite content for highest dynamic mechanical and tensile performance. Curing characteristics of the MREs were determined by moving disk rheometer (MDR 2000), and thermal properties were evaluated by thermogravimetric analysis (TGA). Tan δ was measured through parallel and plate rheometer over a frequency range of 0.1–100 Hz and a strain amplitude range of 0.1–6%. Tensile properties were measured with a universal tensile tester. The results revealed that tan δ, tensile properties, and thermal stability of the MREs increased with increase of waste nickel zinc ferrite contents. Anisotropic MREs, which had chain-like columnar structures of magnetic particles in the matrix as a consequence of an applied magnetic field during curing, were found to produce higher dynamic mechanical performance compared with isotropic MREs cured in the absence of a magnetic field.

Influence of matrix viscosity on the dynamic mechanical performance of magnetorheological elastomers

ABSTRACTAnisotropic magnetorheological elastomers (MREs) with different natural rubber matrix viscosities and industrial waste nickel zinc ferrite were prepared in order to assess the dynamic and mechanical performance of the materials. The curing characteristics of the anisotropic MREs were determined using a moving disk rheometer (MDR 2000). The loss tangent (tan δ) was measured through a parallel‐plate rheometer over a frequency range of 1─100 Hz (Hz) and a strain amplitude range of 0.1─6%. It was found that tan δ increased with increasing matrix viscosity over the range of frequency and strain amplitude explored. Furthermore, as the matrix viscosity increased, the height of the tan δ peak also increased and the glass transition temperature (Tg) valued shifted to a higher temperature. It was also found that tensile strength and elongation at break increased with increasing matrix viscosity. The SEM micrographs revealed that the columnar structures became longer and thicker with a decrease in matrix viscosity. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48492.

Impact energy absorption of functionally graded chiral honeycomb structures

Auxetic chiral structures with negative Poisson ratio (NPR) can contract its width along the directions perpendicular to compression loading direction, thus generate enhanced indentation resistance and enhanced impact energy absorption abilities. To enhance the dynamic mechanical performances of periodic anti-chiral structures and hybrid-chiral structures, geometrically graded ligaments are proposed, and the in-plane dynamic deformation mechanism and energy absorption capacity of the functionally graded anti-chiral and hybrid-chiral cellular structures are studied through finite element analysis (FEA). Numerical results in our work show that the crushing energy absorption performances of periodic chiral structures can be improved by introducing structural graded design, where the plateau stress and energy absorption efficiency can be optimized by means of adjusting the unit cell geometrical parameters. Our study can enrich insightful understanding of the dynamic behavior of chiral cellular materials, and can be employed for optimizing the design of automobile crash energy absorption and impact protection structures.

Crystal-Plasticity-Based Dynamic Constitutive Model of AZ31B Magnesium Alloy at Elevated Temperature and with Explicit Plastic-Strain-Rate Control

In this study, a series of experiments were carried out on the AZ31B magnesium alloy, including both a macro-experiment (mechanical experiment) and a micro-experiment (dislocation observation). Next, based on the consideration of the deformation mechanism of magnesium alloys (dislocation slip and twinning), a dynamic constitutive model of the magnesium alloy was established. In the developed model, the strain-rate-sensitivity control and the effect of temperature on the dynamic mechanical performance of the alloy were also investigated. The model parameters were determined by fitting the macroscopic experimental results. Next, the evolution of the micro-deformation mechanism was calculated by the developed model, and the trend of macro-mechanical behavior was also discussed.

High-performance fully bio-based poly(lactic acid)/ polyamide11 (PLA/PA11) blends by reactive blending with multi-functionalized epoxy

Abstract Bio-based polyamide11 (PA11) was incorporated to enhance and toughen poly(lactic acid) (PLA). Fully bio-based PLA/PA11 blends of high strength and toughness were prepared by reactive blending using reactive multifunctional epoxy compatibilizer. The mechanical properties, dynamic mechanical performance, and phase morphologies and compatibility of PLA/PA11 blends were investigated. Although “self-compatibilization” may exist in binary blends of PLA/PA11, the properties of PLA/PA11 binary blends were not improved due to the immiscibility and poor compatibility between the two polymers. The interfacial compatibility of PLA/PA11 blends was greatly enhanced by the reactive multifunctional epoxy compatibilizer. The fine average particle size and narrow distribution of PA11 dispersed phase could be obtained in the presence of compatibilizer. The compatibilized PLA/PA11 blend exhibited significantly improved tensile strength, elongation at break, and notch impact strength with values of 77.57 MPa, 454.41%, and 9.59 kJ/m2, respectively, compared with those of 58.26 MPa, 13.64%, and 2.97 kJ/m2 for neat PLA, respectively. The enhancement and toughening were attributed to excellent interfacial adhesion and the resultant morphologies with transition from typical sea-island morphology to strip form. Our work provides an effective method to greatly improve the mechanical properties with high strength and toughness, which is very important for the wide application of PLA polymeric materials.

Dynamic Mechanical Performance of Self-compacting Concrete Containing Crumb Rubber under High Strain Rates

The parameters of dynamic mechanical performance at high strain rates are of significant importance in the structural designs and numerical simulations. The aim of this paper is to study the strain rate sensitivity of self-compacting rubberized concrete (SCRC) in the dynamic compressive, splitting tensile and bending tests by using the split Hopkinson pressure bar (SHPB) technique. The failure modes, stress-strain curves and dynamic strength changes of SCRC under various loading conditions were also observed. The specific energy absorption, dynamic tensile-compressive strength ratios, and dynamic constitutive model of SCRC with different rubber content were also analyzed. The results indicate that SCRC can exhibit stronger strain rate sensitivity compared to SCC when strain rate is enough high, while the strain rate sensitivity of SCRC is lower than that of SCC at when strain rate is less than a critical value. To understand the strain rate sensitivity of SCRC, dynamic constitutive model (ZWT model) based on nonlinear viscoelastic theory was proposed. For impact toughness, although the specific energy absorption decreases with increasing rubber content, the ratios of tensile strength to compressive strength of SCRC have an increasing tendency when rubber content increases.

Thermally exfoliated graphene oxide reinforced stress responsive conductive nanocomposite hydrogel

Lightweight and flexible biosensors that can sustain mechanical deformation and can be adhered to human skin is an interesting field of study. In the current article, a systematic study on development of thermally exfoliated graphene oxide (TEGO)–reinforced poly(vinyl alcohol) (PVA)–based conductive hydrogel nanocomposites has been reported. The free‐standing hydrogels were synthesized using controlled and repetitive freeze‐thaw cycles. The samples were then studied for their mechanical as well as electrical properties. The hydrogels were characterized for their microstructural, chemical, and rheological properties to understand the observed macroscopic properties. Additionally, a study on the behavior of hydrogels immersed in phosphate‐buffered saline (PBS) was carried out to investigate their hydrolytic stability within simulated biological environment. Overall, the nanocomposite hydrogels demonstrated excellent static and dynamic mechanical performance, stability in PBS, considerable electrical conductivity, and significant electrical response to applied external stress, establishing their potential for use as flexible biosensors.

Effect of Plasticizer on Microstructure and Dynamic Mechanical Performance of Anisotropic Magnetorheological Elastomers

Anisotropic magnetorheological elastomers (MREs) based on natural rubber and industrial waste nickel zinc ferrite were prepared. Paraffin oil was employed as plasticizer to modify the viscosity of rubber matrix. The amount of plasticizer was varied at five levels (5, 10, 20, 30 and 40 phr) to assess the ability of nickel zinc ferrite particles to align into chain like columnar structures within the rubber under an applied magnetic field. Scanning electron microscopic (SEM) and dynamic mechanical analysis over frequency range of 1-100 Hz and a strain amplitude range of 0.1-6% were examined. SEM micrographs revealed that the chain like columnar structures become longer and thicker as the viscosity of the rubber matrix decreased. It was found that 5 phr plasticizer produced the highest tan δ over the range of frequency and strain amplitude explored.

Frequency and Amplitude Dependence of Magnetorheological Elastomers Composites

In this study, anisotropic and isotropic magnetorheological elastomers (MREs) based on nickel zinc ferrite and natural rubber were prepared. The amount of nickel zinc ferrite was varied at five different levels (20, 40, 60, 80, and 100 phr) to assess its optimum content for enhancing dynamic mechanical performance of MREs. Tan δ was measured through parallel plate rheometer over frequency range of 0.1-100 Hz and strain amplitude range of 0.1-6%. The results revealed that tan δ increased with increasing waste nickel zinc ferrite content and reached maximum value at 100 phr for both isotropic and anisotropic MREs. SEM micrograph showed that anisotropic MREs had chain-like columnar structures of magnetic particles in the matrix as a consequence of an applied magnetic field during curing. For frequency sweep test, tan δ for anisotropic MRE improved 244% and for strain amplitude test 159% improvement compared to isotropic MRE.

Effect of elevated operating temperature on the dynamic mechanical performance of E-glass/epoxy composite

The construction industry has seen a proliferation of continuous and discontinuous fiber-reinforced polymer composites due to their high strength-to-weight and stiffness-to-weight ratios while being resilience to harsh environmental and operating conditions. This paper reports a comparative experimental investigation of field-deployed E-glass/Epoxy composite panels with those freshly manufactured to elucidate the effect of deployment conditions on the performance of these panels. Samples extracted from underground vault after power-line explosion due to arcing fault were examined using optical and atomic force microscopes to assess the extent of the damage. The samples were also characterized using a dynamic mechanical analyzer to explain the change in the properties post-explosion quantitatively. Microscopy investigations show no significant change in morphology or topography of the panels as well as the absence of failure modes such as delamination, fiber-failure or core-failure. Nonetheless, surface contaminations due to service conditions were found to exaggerate the surface burn marks despite the fire retardation properties of the composite panels. The dynamic mechanical properties of the panels were found to change as a function of temperature and loading frequency slightly. A shift in transition temperatures (Tβ and Tg) was found to be within a few degrees Celsius. The storage modulus was reduced by 21%, while the overall complex modulus remained relatively constant when comparing fresh and field-deployed samples. A frequency and temperature dependent model was used to fit the dynamic data and found to provide insights into the microstructure evolution of the polymer matrix.

Dynamic mechanical characteristics of filling layer self-compacting concrete under impact loading

Filling layer self-compacting concrete (FLSCC) is a key construction material in China Rail Track System (CRTS) III slab ballastless track and its resistance to impact loading is of great importance to the service security of high-speed train. In this paper, the dynamic mechanical characteristics of FLSCC under impact loading were investigated with a split Hopkinson pressure bar (SHPB) at strain rates ranging from 101s−1 to 102s−1. Results show that the compressive strength, peak strain, elastic modulus and toughness ratio of FLSCC all increase with strain rate. The increase factors of compressive strength (DIFc) and strain (DIFɛ) of FLSCC increase linearly with decimal logarithm of strain rate. The elastic modulus (Ed) and toughness ratio (TR) increase linearly with strain rate. Self-compacting concrete (SCC) shows greater strain rate effect than normal concrete (NC). However, FLSCC presents lower strain rate effect but better toughness performance than normal SCC. The incorporation of large content of SP and VMA provides FLSCC with higher porosity, which makes it possess excellent dynamic mechanical performance.

Effects of MAH/St grafted nanocellulose on the properties of carbon reinforced styrene butadiene rubber

Abstract Nanocellulose was extracted from bagasse (bagasse nanocellulose, BNC) by hydrolysis with alkali and acid, then grafted by maleic anhydride (MAH) and styrene (St). The modified nanocellulose (BMS) was further investigated to partially replace carbon black (CB) in St butadiene rubber (SBR) composites via coagulation to prepare SBR/BMS/CB composites. Through the comparison of the vulcanization characteristics, processing properties, mechanical properties, and dynamic mechanical performance of them, BMS proved to be more efficient than BNC. The results showed that BMS could activate the vulcanization process, suppress the Payne effect, and increase the modulus and hardness. Moreover, a fine BMS dispersion and strong interfacial interaction were achieved in SBR/BMS/CB composites. The observed reinforcement effects were evaluated based on the results of G′, tanδ and scanning electron microscopy (SEM) analyses of SBR/BMS/CB in comparison with SBR/BNC/CB composites.

Dynamic behavior of CHS-SHS tubular T-joints subjected to low-velocity impact loading

Welded steel tubular structures are easily exposed to impact loading which may cause devastated damage firstly to their connecting joints. The critical joints determine the dynamic mechanical performance of the structures in those unexpected catastrophes. This paper describes an experimental and numerical impact investigation on dynamic behavior of CHS-SHS tubular T-joints, made up of a circular hollow section (CHS) brace and a square hollow section (SHS) chord. Seven CHS-SHS tubular T-joint specimens with different geometric and loading properties were tested on an in-house dropped hammer testing machine. The deformation mode of the joint specimens was identified as outward buckling of the chord side walls and indentation of the chord top surface. The experimental results indicated that increasing the geometric parameter β (the width ratio of the brace to chord) enhanced the impact resistance, increasing the impact velocity significantly affected the dynamic response, and changing the boundary condition had little effect on the dynamic performance of the joints. Six finite element (FE) models of the tested joint specimens were developed to simulate the dynamic behavior of the joints. The comparison of the impact force, displacement development, and deformation mode showed that the FE analysis was in good agreement with the experimental results. A parametric study was subsequently conducted to quantify the effects of the impact velocity, impact mass, and impact energy on the dynamic performance of the joints. The numerical results showed that the impact force, displacement, and energy dissipation were linearly dependent on the impact energy of the dropped hammer, and the impact duration of the impact process was directly correlated to the impact momentum.

Synthesis and characterization of novel renewable tung oil-based UV-curable active monomers and bio-based copolymers

With the rapid development of industry and the growing shortage of fossil energy, tung oil has attracted much attention of researchers because of its environment-friendly and renewable advantages. In this work, we successfully synthesized two kinds of tung-oil-derived renewable UV-curable active monomers, tung-acid-maleic tri-acrylate (TOAH) and tung-maleic tetra-acrylate (TMPG). 1H NMR and FT-IR results collectively revealed that the targeted active-monomers were successfully prepared. UV-curing kinetics of the films was studied by Photo-DSC, thermal properties of their cured films were investigated by dynamic mechanical analysis, thermogravimetric analysis and general performance of UV-curing films including acidic, alkaline resistance and boiling-water resistance were also investigated. Tensile properties of the cured films were also tested. Dynamic mechanical analysis demonstrated that the storage modulus and glass transition temperatures of the cured films increased while increasing the content of TMPG monomer. The crosslinking density of the cured copolymers also increased with the increasing content of TMPG monomer. TGA showed that the maximum thermal decomposition temperatures (Tmax) of the cured copolymers were all above 420 °C. Tensile tests indicated that the tensile properties were better in the cured systems when the mixed films consisted of 50TOAH/50TMPG and 30% HDDA reactive diluent. Finally, all the results demonstrated that comparable balanced properties could be obtained by mixing these two bio-based monomers together.

Effect of hydrothermal aging on the dynamic mechanical performance of the room temperature-cured epoxy adhesive

To evaluate the performance and reliability of a new type of epoxy resin adhesive, the dynamic mechanical analysis (DMA) testing was performed at different levels of temperature and frequency after hydrothermal aging. The results of the DMA and the thermodynamic analysis that the performance of the adhesive has little change after hydrothermal aging for 30 days meant that the resistance to hydrothermal aging of this adhesive was excellent. In addition, the time-temperature equivalence principle and time-aging time equivalence principle were proposed here to offer additional insights into the dynamic mechanical performance of the newly developed adhesive. Moreover, an effective method by which the generalized curve of definite aging time in certain conditions of definite temperature and humidity can be obtained was introduced.

Experimental and Theoretical Analysis on the Dynamic Characteristics of Fused Filament Fabrication Plates

With the increasingly wide application of fused filament fabrication (FFF) technique, the built products are inevitably exposed to dynamic mechanical loading and vibration. However, there has been no systematic study in the literature on understanding and characterization of dynamic mechanical performance for FFF products. In this paper, the dynamic characteristics of FFF plates are quantified, with the effect of different extrusion width taken into account. A dynamic model of the built plate with cantilever boundary conditions is established, and the inherent characteristics are predicted. Modal tests are then performed on these samples to obtain the measured data. Through the comparison between predictions and measurements, the theoretical model is validated. Different extrusion width makes the material properties of the plates different, resulting in different dynamic characteristics. The scanning electron microscopy (SEM) analysis on the samples confirms that the dynamic characteristic is deteriorated as the extrusion width decreases. This present work provides theoretical basis and technical support for further research in improving the dynamic performance of FFF products and helps extend the applications of this technique.