Dynamic Mechanical Analysis Tests Research Articles

Synergistic reinforcing and cross-linking effect of thiol-ene-modified cellulose nanofibrils on natural rubber

To achieve synergistic reinforcing and cross-linking effect across interface between hydrophilic nanocellulose and hydrophobic rubber, active thiol groups were introduced at reducing end of CNF while retaining hydroxyl groups on the surface, thus forming a percolation network in nanocomposites. The nanocomposites were obtained by casting/evaporating a mixture of dispersed modified CNF and NR in latex form, in which covalent cross-links were formed between thiol groups and double bonds of NR via photochemically initiated thiol-ene reaction. Strong interfacial interaction between NR matrix and end-modified CNF was characterized by Fourier-transform infrared spectroscopy. The structural and mechanical properties of the nanocomposites were evaluated by scanning electron microscopy, dynamic mechanical analysis and tensile tests. Compared to neat NR, the nanocomposite reinforced with 10 wt% modified CNF showed significantly higher values of tensile strength (0.33 to 5.83 MPa), Young's modulus (0.48 to 45.25 MPa) and toughness (2.63 to 22.24 MJ m−3).

Novel polyimide in presence of benzoxazole: Synthesis and characterization

Dianhydride (3′, 4, 4′-biphenyltetracarboxylic dianhydride (BPDA) and Diamine (p-phenylediamine (PDA) in a ratio of 1:1 polymerize Polyimide (PI) in N-Methyl-2-Pyrrolidone (NMP) as solvent. A series of PI films were made in presence of BPDA and two types of Diamines (PDA and HAB (4, 4′-Diamino-3, 3′-dihydroxybiphenyl) where Diamines ratios were 95:5, 90:10, 80:20, 50:50, 0:100. HAB was introduced as source of benzoxazole. Fourier transform infrared (FTIR) confirmed that there was benzoxazole ring in polyimide after curing. FTIR, Differential scanning calorimetry (DSC), UV-spectrophotometer, Scanning electronic microscope (SEM), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and stress-strain tests were used to measure the performance of the films. The results indicated that small content of benzoxazole (5%) increase thermal stability, glass transition temperature and tensile strength prominently than the pristine PI which may use for microelectronics.

Mechanical Performance of Fused Filament Fabricated and 3D-Printed Polycarbonate Polymer and Polycarbonate/Cellulose Nanofiber Nanocomposites

In this study, nanocomposites were fabricated with polycarbonate (PC) as the matrix material. Cellulose Nanofiber (CNF) at low filler loadings (0.5 wt.% and 1.0 wt.%) was used as the filler. Samples were produced using melt mixing extrusion with the Fused Filament Fabrication (FFF) process. The optimum 3D-printing parameters were experimentally determined and the required specimens for each tested material were manufactured using FFF 3D printing. Tests conducted for mechanical performance were tensile, flexural, impact, and Dynamic Mechanical Analysis (DMA) tests, while images of the side and the fracture area of the specimens were acquired using Scanning Electron Microscopy (SEM), aiming to determine the morphology of the specimens and the fracture mechanism. It was concluded that the filler’s ratio addition of 0.5 wt.% created the optimum performance when compared to pure PC and PC CNF 1.0 wt.% nanocomposite material.

Study on the Thermal and Impact Resistance Properties of Micro PA66/PU Synergistically Reinforced Multi-Layered Biaxial Weft Knitted Fabric Composites

Abstract In this paper, the influence of micro PA66/PU in multi-layered biaxial weft knitted (MBWK) fabric reinforced composites on thermal and impact resistance was studied. The main objective was to investigate the role of micro PA66/PU in terms of improving material performance. The results showed that the addition of micro PA66/PU improved the thermal stability of the MBWK composite. It is observed that the onset degradation temperatures increased by 1.6°C in thermo-gravimetric analysis (TGA) test and the Tg increased by 2.8°C in the dynamic mechanical analysis (DMA) test. Besides, the impact energy absorption of composites increased by 5.3% after the addition of micro PA66/PU. The addition of micro PA66/PU effectively reduced the impact damage area from the failure morphology after impact. In simple words, the addition of micro PA66/PU effectively improves the comprehensive properties of composites.

Modeling of viscoelastic behavior of a shape memory polymer blend

AbstractShape memory effect (SME) of polymers is a property that concerns both, macroscopic and microscopic changes. The variation of internal polymer properties such, as molecular weight (Mw), rigidity, and viscoelasticity could alter its SME. In this study, a bi‐parabolic model with six parameters is used to describe the viscoelastic behavior of a shape memory polymer (SMP) blend (40% poly(caprolactone), PCL/60% Styrene–Butadiene–Styrene) with different PCL Mw. These parameters are determined using the Cole–Cole method. Modeling curves (E″ = f (E′)) will be then compared to experimental data from dynamical mechanical analysis (DMA) tests. It is shown that the bi‐parabolic model predicts well the behavior of the SMP mixture for different Mw of PCL. Afterwards, the evolution of the model parameters with the Mw of PCL is investigated. It is revealed that, when Mw of PCL drops, the relaxation modulus E0 increases. This result proves that the rigidity of the SMP blend rises with Mw declines.

Improving interfacial properties of polyarylene ether nitrile/aramid fiber composite through hydrogen bonding interaction combined with molecular weight adjustment

Aramid fiber (AF)-reinforced composite is a material with high performance and great potential. In this work, polyarylene ether nitrile terminated with phthalonitrile (PEN-t-Ph) is used to modify the AF surface, and hydrogen bonds are formed between the AF and PEN-t-Ph resin, as shown by Fourier infrared analysis. Then modified AF (m-AF)/PEN-t-Ph composite laminate is prepared by hot-pressing, and the influence of molecular weight of PEN-t-Ph on performance of the m-AF/PEN-t-Ph composite laminate is studied. The PEN-t-Ph were named PEN-1, PEN-2, PEN-3 and PEN-4 according to molecular weight from large to small. And the mechanical properties and interface compatibility of m-AF/PEN-n composite laminates initially increase and then decrease as the molecular weight of the PEN-t-Ph resin decreases. The m-AF/PEN-3 composite laminate has the best mechanical performance with an interlaminar shear strength of 94 MPa that is 95% higher than the lowest values among the four samples. In addition, m-AF/PEN-3 has the best impact strength of 133.70 kJ/m2, and in the dynamic mechanical analysis test, m-AF/PEN-3 has a leading storage modulus with 62 GPa at 120 °C which is 50 GPa higher than for the lowest sample. In general, the molecular weight of the PEN-t-Ph resin has a greater impact on performance of the m-AF/PEN-t-Ph composite laminates, and appropriate adjustment of molecular weight of the PEN-t-Ph resin will help improve the comprehensive performance of the m-AF/PEN-t-Ph composite laminate and provides a new way for preparing AF-reinforced materials.

An experimental study of De-Icing property using Reduced Graphene Oxide - Boron Nitride Nano Powder in CFRP

Icing is one of the critical factors that affects the flight of the aircraft in ways of drag. In this study, the rate of de-icing was experimented with the composite material using Boron Nitride Nano Powder (BNNP) and Reduced Graphene Oxide (rGO). Boron Nitride are highly thermal conductive and lesser toxic, and Graphene allows to be a good conductor of heat and electricity and thereby, these nanomaterials are used as a filler for de-icing application. The filler is mixed in Epoxy Resin using ultrasonicator. In order to get better specimen surface of composite, ultrasonic mixing method is used instead of hand-mixing. To fabricate Carbon Fiber Reinforced Polymer (CFRP) Hand Lay-up Method is carried out. The material characterization is done by X-ray Diffraction (XRD), and Scanning Electron Microscope (SEM). Mechanical properties are studied with Dynamic Mechanical Analysis (DMA), Thermo-Gravimetric Analysis (TGA), and Water Droplet test. Moreover, the Carbon Fiber Reinforced Polymer surface shows extraordinary de-icing effect contrasted with the non-functionalized surface. This study has proved that the de-icing property is very much effective with Carbon Fiber Reinforced Polymer where Graphene and Boron Nitride as the filler.

Investigation on dynamic mechanical analysis of bio-active coating materials coated on Teflon, PVC and Nylon polymers

Selection of Bio-active coating materials plays a vital role in order to improve the life span and mechanical properties of Bio-material implants. Bio-active coating is extensively coated on the Bio-polymers such as Nylon, Polytetrafluoroethyene (Teflon) and polyvinyl chloride (PVC) to form a thin film barrier where Hydroxyapatite (HAP) is used as Bio-coating material, which is very expensive and poor in viscoelastic behavior and damping co-efficient. The objective of this paper is to select the alternative Bio-coating material by using Aluminum Oxide, Egg and Sea Shell which are easily available in nature and economical. Selected Bio-active materials are used to protect the surface area of the Bio-implant. Plasma spray technology is used to coat the Teflon, Nylon and PVC with selected coating materials. Dynamic Mechanical Analysis (DMA) test conducted on both coated and uncoated samples to examine the viscoelastic behavior and damping co-efficient of samples where Teflon, Nylon and PVC coated with Al2O3, Egg Shell and Sea Shell showed better results when compared to Hydroxyapatite (HAP).

Temperature dependency of the toughening capability of electrospun PA66 nanofibers for carbon/epoxy laminates

The present study evaluates the toughening capability of electrospun PA66 nanofibers for carbon/epoxy composite laminates subjected to mode II loading conditions at elevated temperatures. The Dynamic Mechanical Analysis (DMA) test showed that the glass transition temperature of the produced nanofibers is in a range of ∼60–80 °C. Accordingly, End-Notched Flexure (ENF) carbon/epoxy specimens interleaved by a 50 μm-layer of electrospun PA66 nanofibers were subjected to the quasi-static mode II loading at room temperature (∼25 °C), 100 °C, 125 °C, and 160 °C. At room temperature, the mode II interlaminar fracture toughness (GIIC) of the nano-modified specimen was ∼4 times higher than the virgin specimen (non-modified) (3.12 kJ/m2 vs 0.81 kJ/m2). The results showed that GIIC of the virgin specimen was independent of temperature. However, in the case of the nano-modified specimen, although the GIIC did not change from room temperature to 100 °C (3.12 kJ/m2 vs 3.09 kJ/m2), by further increasing temperature to 125 °C and 160 °C, GIIC dropped by 34% and 43% respectively (2.05 kJ/m2 and 1.77 kJ/m2 respectively). 3D surface scans and Scanning Electron Microscopy (SEM) images of the fracture surface revealed three reasons for decreasing the toughening capability of the PA66 nanofibers at high temperatures: a) the crack crosses the nano-layer less at high temperatures, b) the dominant damage mechanism at low temperature is “cohesive failure”, the damage propagation within the nanolayer, while at higher temperatures “adhesive failure”, the debonding of the nanolayer from carbon fibers, plays a critical role in the fracture, and c) severe plastic deformation of nanofibers at high temperatures.

New lignin-based hybrid materials as functional additives for polymer biocomposites: From design to application

Within this study, the ZrO2/lignin and ZrO2-SiO2/lignin hybrid materials were obtained for the first time. The mechanical grinding method was used for this purpose. In order to determine the properties of obtained lignin-based hybrids and the components used to produce them, as well as to evaluate the efficiency of their preparation, the authors used such research techniques as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), elemental analysis, porous structure analysis and thermal stability assessment (TGA/DTG). The next step involved using the components and produced hybrid materials as polymer fillers for poly(methyl methacrylate) (PMMA). The obtained lignin-based hybrid biocomposites have then been thoroughly characterized using gel permeation chromatography (GPC), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and hardness testing. All the conducted tests confirm the possibility of using the obtained bio-based products in practice, within the widely understood construction industry, for producing durable building facades or noise barriers, among others.

Soft-tissue-mimicking using silicones for the manufacturing of soft phantoms by fresh 3D printing

PurposeThe purpose of this study is to use the Freeform Reversible Embedding of Suspended Hydrogels (FRESH) additive manufacturing (AM) technique for manufacturing a liver phantom which can mimic the corresponding soft living tissue. One of the possible applications is surgical planning.Design/methodology/approachA thermo-reversible Pluronic® F-127-based support bath is used for the FRESH technique. To verify how three-dimensional (3D)-printed new materials can mimic liver tissue, dynamic mechanical analysis and oscillation shear rheometry tests are carried out to identify mechanical characteristics of different 3D printed silicone samples. Additionally, the differential scanning calorimetry was done on the silicone samples. Then, a validation of a 3D printed silicone liver phantom is performed with a 3D scanner. Finally, the surface topography of the 3D printed liver phantom was fulfiled and microscopy analysis of its surface.FindingsSilicone samples were able to mimic the liver, therefore obtaining the first soft phantom of the liver using the FRESH technique.Practical implicationsBecause of the use of soft silicones, surgeons could practice over these improved phantoms which have an unprecedented degree of living tissue mimicking, enhancing their rehearsal experience before surgery.Social implicationsAn improvement in surgeons surgery skills would lead to a bettering in the patient outcome.Originality/valueThe first research study was carried out to mimic soft tissue and apply it to the 3D printing of organ phantoms using AM FRESH technique.

Microstructure and performance of epoxy asphalt binders modified by core-shell rubbers containing different core polymers

Core-shell rubber (CSR) is a good candidate for toughening epoxy asphalt binders. However, the knowledge of the effect of the core polymer on the performance of CSR modified hot-mix epoxy asphalt binder (HEAB) is not completed and systematic yet. In this paper, CSR modified HEABs were prepared by the incorporation of 2 wt% CSR particles with different core polymers, which were in turn subjected to viscous measurements, confocal microscopy, thermogravimetric analysis, dynamic mechanical analysis and tensile tests. The results revealed that the viscosity of CSR with styrene-butadiene copolymer (SB) core (CSRSB) modified HEAB is higher than that of CSR with polybutadiene (PB) core (CSRPB) modified HEAB during curing. The shell destruction of CSR particles resulted in the swelling of the core polymers and dispersion of swollen core polymer particles in the epoxy phase in the micron scale along with asphalt particles. The phase separation of CSRPB modified HEAB occurred in the spinodal decomposition mode, which was different from the nucleation and growth mechanism of the neat and CSRSB modified HEABs. The area fraction of swollen PB particles in the CSR modified HEAB was greater than that of swollen SB particles. The core polymer had a negligible effect on the thermal stability of CSR modified HEABs. The glass transition temperatures of epoxy and asphalt, damping ability and mechanical properties of the neat HEAB were increased with the addition of CSR particles. Especially, CSRPB modified HEAB had higher tensile strength and toughness than CSRSB modified HEAB. With 2 wt% CSRPB particles being adding, the tensile strength, elongation at break and toughness of the neat HEAB were increased by 53%, 42% and 110%, respectively.

Crosslink density and mechanical property evolution during the curing of polyurethane-urea/sodium silicate hybrid composites

In order to understand the evolution of the structure–property relationship between the crosslink density and mechanical properties of polyurethane-urea/sodium silicate (PU/SS) hybrid composites, a series of PU/SS composites with 2.5 wt% organofunctional silanes and pure PU/SS composites are investigated at different curing time. Mechanical properties, the fracture surface morphology, and thermo-mechanical properties of these PU/SS composites are characterized by electron omnipotence experiment machine, scanning electron microscope, and dynamic mechanical analysis (DMA), respectively. The mechanical test results show the strength and fracture toughness of the PU/SS composites first increase and then stabilize during cure, and the modification leads to PU/SS composites with significantly higher mechanical properties. Further, the morphology of fractured samples also reveals that the longer curing time and the modification of the PU/SS composites means a higher curing degree. Moreover, the increase in the crosslink density calculated from the DMA tests quantitatively confirmed the positive influence of the curing time and the modification in enhancing mechanical properties. In addition, it is also found that the mechanical properties of the PU/SS composites not only depend on the crosslink density but also on the well-dispersed hybrid PU/SS system.

Enhancing shape memory properties of multi-layered and multi-material polymer composites in 4D printing

The shape memory behavior of smart materials is widely used for stimulation or shape-shifting purposes. Shape memory polymers (SMPs) can shape and force recoveries accompanied by attractive attributes such as biocompatibility, biodegradability, and universality. In this paper, a thermoplastic elastomer (TPE) is used as a complementary material for 4D printed polylactic acid (PLA) structures to enhance their shape and force recovery properties and lower the stimulation temperature for more practical implementations. Two approaches are followed to provide SMP composites (SMPCs): multi-layered and multi-material lattices. In multi-layered lattices, specimens are comprised of separate layers and different ratios of SMP and TPE materials. For comparison, PLA-TPE filaments with the same ratios of multi-layered lattices are produced and used to fabricate multi-material lattices. Dynamic mechanical thermal analysis tests showed a reduction in the glass transition temperature of the manufactured PLA-TPE filament. X-ray diffraction test was conducted to prove that the crystallinity of the developed PLA-TPE material increases which explains the better shape memory effect in the multi-material specimens. Phase separation occurred in low ratios of TPE in PLA, discernible in field emission scanning electron microscope (FESEM) images, resultting in low quality in one of the developed PLA-TPE filaments. FESEM images also showed proper miscibility of TPE in PLA in higher ratios. Thermomechanical tests were done on printed specimens to examine and compare the shape and force recovery of the produced SMPCs. While the shape recovery of multi-material samples was not as good as multi-layered samples, both approaches have better shape recovery results than the PLA sample. Due to a lower glass transition temperature in multi-material lattices, their shape recovery process started at lower temperatures widening their potential practical applications. Force recovery of multi-material samples revealed a significant improvement which was due to more oriented crystalline polymer structures.

Characterization of polymeric biomedical balloon: physical and mechanical properties

Abstract Tubes from nylon 12 and Pebax 6333 resins were produced using an extrusion process. The extruded tubes were used to produce balloons for angioplasty applications. The tubes were stretched using blow molding process to produce balloons. Melt rheology behavior for nylon 12 and Pebax were studied and nylon 12 showed a more pronounced shear thinning behavior compared to Pebax. Orientations of the tubes and the balloons were assessed using Fourier transform infrared spectroscopy (FTIR) and it was found that nylon material is more sensitive to molecular orientation when stretched compared to Pebax material. Melting behavior for the tubes and balloons were investigated using dynamic scanning calorimetry (DSC). The melting temperature shifted to higher temperatures when the tubes are stretched into balloons and the shift was more pronounced for Pebax balloon than nylon. Morphology of Pebax balloon surface revealed a hybrid structure consisting of hard segments dispersed in soft segments and amorphous phases. The hard segments are crystallized polyamides that are biaxially oriented in the balloon with higher molecular orientation in the radial direction compared to axial direction. This resulted in a higher tensile strength along the radial direction compared to axial for the balloons. Dynamic mechanical analyzer (DMA) tests showed that the glass transition temperature of the nylon tubes shifted to higher temperatures (from 51 to 82 °C) during the balloon forming process, which means the nylon becomes stiffer and less flexible when formed into a balloon.

Experimental identification of the material standard linear solid model parameters by means of dynamical measurements

A procedure for the experimental identification of the material standard linear solid model parameters by means of dynamic mechanical analysis test instrument measurements is presented. Since the standard linear solid material stress–strain functional D(ω) relationship in the frequency domain formally depends on the standard linear solid material parameters, a procedure able to identify these parameters from test measurement estimates is proposed in this work. Nevertheless, a critical, nonlinear and non-parametric approach is to be followed since the number of the material standard linear solid block components is generally unknown, and the material D(ω) shows a highly nonlinear dependency on the unknown standard linear solid material parameters. For these reasons, measurement and test model noise is expected to strongly influence the accuracy of the identification results. A multi-step procedure is presented, consisting first in the non-parametric identification of a frequency dependent, two degrees of freedom model instrument frame by means of a polynomial rational function, where polynomial order and parameters, such as polynomial coefficients and pole-residue couples, are optimally identified by means of an algebraic numerical technique and of an iterative stabilization procedure. Another procedure able to identify the material D(ω) polynomial rational functional relationship in the frequency domain is also proposed, taking into account the dynamic contribution of the instrument frame, of the inertial contribution of the distributed mass of the beam and of the lumped mass of the instrument force measuring system. An effective procedure, able to identify the standard linear solid material model parameters in the time domain from the identified material physical poles, is finally proposed. Some application examples, concerning the identification of the standard linear solid model of a known material and of an unknown composite material, are shown and discussed as well.

Graphene으로 개질된 폴리우레탄-에폭시 복합체의 기계적 물성과 Damping 특성

Polyurethane (PU) has received extensive attention in structural engineering due to its excellent mechanical properties and damping properties. In this research, graphene-modified PU-epoxy composites are prepared for the application in structural engineering. The mechanical properties and damping properties of the composites with different contents of graphene are investigated. The damping properties of the composites were also investigated by performing dynamic mechanical analysis (DMA). The results showed that with the increase of graphene content, the tear strength of the composites decreased from 52 to 39 ㎫. Due to the enhancement of appropriate amount of graphene, the tensile strength and elongation at break increase to the maximum value, being 16 ㎫ and 675%, respectively. And DMA tests showed that the damping properties reach the optimal values when the graphene content is 0.2%. The large damping temperature range (ΔT<SUB>0.5</SUB>) is 33 ℃, from -2.9 to 30.1 ℃. The peak of loss factor (η<SUB>max</SUB>) is 0.92 and the integral area (TA) is 36 ℃, much higher than those of the pure PU-epoxy composites. In addition, scanning electron microscopy (SEM) results show that agglomeration appears with higher graphene content.

Damping characteristics of carbon nanotube reinforced epoxy nanocomposite beams

In this paper, theoretical and experimental studies are carried out to investigate the damping characteristics of carbon nanotube (CNT) reinforced epoxy nanocomposite beams. A modified Biot model is proposed to simulate the frequency-dependent damping characteristics of CNT reinforced epoxy nanocomposites and implemented into the finite element model for composite beams. The natural frequencies and modal damping ratios of CNT reinforced epoxy beams are predicted using the proposed finite element model. Then, CNT reinforced epoxy beam specimens are fabricated, upon which dynamic mechanical analysis and vibration tests are carried out. Comparison studies between theoretical and experimental results show that modified Biot model proposed here is more accurate than the original one in predicting loss factors of CNT reinforced epoxy nanocomposites. It is revealed that the damping ratios associated with the first three vibration modes of composite beam specimens initially increase and then decrease with the increment of CNT weight ratio. The first order damping ratio with 0.4 wt% CNT reinforcement has the maximum value of 0.591%, which is improved by 41% compared with that of pure epoxy.

Mechanical behavior of carboxylic functionalized graphene reinforced polyurethane nanocomposites under static and dynamic loading

AbstractThe present work reports formation of polyurethane (PUR) and carboxylic functionalized graphene (COOH‐fG) nanocomposites via solution mixing method and static and dynamic mechanical characterization with dynamic mechanical analysis (DMA), nano indentation, and tensile and compressive testing. Magnetic stirring of the solutions of PUR in N,N dimethylformamide (DMF) and COOH‐fG in DMF was performed for different compositions of filler, 1%, 3%, 5%, 7%, and 10%, which were heated to obtain nanocomposite films followed by injection molding to cast into samples. Uniform dispersion and good intercalation were observed upon characterization by field emission scanning electron microscopy and X‐ray diffraction techniques. DMA showed that the storage modulus improved with increasing frequency of loading, and a linear decrement in the damping factor with an increase in the concentration of filler was observed. The maximum depth of indent in nano‐indentation test showed a decreasing trend, indicating improvement in nanohardness and elastic modulus with an optimum obtained at 5 wt% composition. An improvement in tensile modulus, tensile strength, and toughness, which were more substantial at lower compositions of filler, was observed. An optimum compressive modulus was obtained for 10 wt% of filler due to more resistance provided by graphene plates to compression as compared to PUR.

Dimensional stability and mechanical performance evolution of continuous carbon fiber reinforced polyamide 6 composites under hygrothermal environment

Abstract This study aimed to investigate moisture absorption behaviors, dimensional stability, and mechanical performance evolution of continuous carbon fibers reinforced with polyamide 6 composites (CF/PA6) under a hygrothermal environment. 3D Fickian model determined the principal three-dimensional (3D) diffusion coefficients by using an optimization algorithm. Three-dimensional changes of samples were measured to quantify the relationship between swelling coefficient and water content. After hygrothermal aging, the tensile properties of PA6 resin and CF/PA6 composites in the transverse direction decreased significantly, but the longitudinal tensile properties of CF/PA6 composites were insensitive to hygrothermal aging. DMA (Dynamic Mechanical Analysis), SEM (Scanning Electron Microscopy) and FTIR (Fourier Transform Infrared) tests were also applied to analyze the mechanism of mechanical properties degradation.