Dynamic Mechanical Analysis Research Articles

Variations in the Thermomechanical and Structural Properties during the Cooling of Shape-Memory R-PETG.

One of the useful features of 3D-printed specimens of recycled polyethylene terephthalate glycol (R-PETG) is the ability to repetitively develop free recovery as well as the work-generating, shape-memory effect. This behavior is enabled by the R-PETG's capacity to stiffen during cooling, thus allowing for a new temporary shape to be induced. Aiming to devise an explanation for the polymer's stiffening, in this study, the variation in some of the R-PETG's parameters during cooling are emphasized and discussed. The evolution of an R-PETG filament's shape was monitored during room-temperature-bending heating-cooling cycles. Straight-shape recovery and the complete loss of stiffness were observed at the start and the end of heating, respectively, followed by the forced straightening of the filament, performed by the operator, around 40 °C, during cooling. The tests performed by dynamic mechanical analysis disclosed the rise of the storage modulus (E') after 100 °C heating followed by either liquid-nitrogen- or air-cooling to room temperature, in such a way that E' was always larger after cooling than initially. Static tests emphasized a peculiar stress variation during a heating-cooling cycle applied in air, within the heating chamber of the tensile testing machine. Tensile-failure tests were performed at -10 °C at a rate of 100 mm/min, with specimens printed at various deposition directions between 10 and 40° to the transversal direction. The specimens printed at 40°, which had the largest ultimate strains, were broken with tensile rates between 100 and 500 mm/min. Deformation rate increase favored the shift from crazing to delamination failure modes. The correlation between the structural changes, the sharp E' increase on heating, and the stiffening induced by cooling represents a novel approach that enables the use of 3D-printed R-PETG for the fabrication of the active parts of low-priced lightweight resettable actuators.

One-pot synthesis of robust silyl ether-based HDPE vitrimers with enhanced performance and recyclability

Vitrimers are thermally reversible crosslinked polymers that combine the performance of thermosets with the benefits of melt (re)processing. However, existing high-storage modulus vitrimers lack this melt-reprocessibility. This study reports on high storage modulus vitrimers obtained by grafting vinyltrimethoxysilane onto high-density polyethylene (HDPE) using silyl ether crosslinker, bis[3-(trimethoxysilyl)propyl]amine. We also explored the effects of 2,2,6,6-tetramethyl-4-piperidinol and diethyl maleate on the performance of these vitrimers. All vitrimers reported herein are prepared in one step via melt-extrusion without the use of any solvent or catalyst. These vitrimers were characterized via differential scanning calorimetry, Fourier-transform infrared spectroscopy, thermogravimetric analysis, dynamic mechanical analysis and mechanical testing. Selected vitrimers were melt-reprocessed six times and assessed for changes in their storage modulus and mechanical strength by industry-relevant extrusion processing. This study is the first of its kind to offer a solvent-free, single-step approach for the synthesis of vitrimers from HDPE. These vitrimers exhibit an impact strength five times higher relative to that of conventional HDPE, a very high storage modulus (1.58 MPa) at 180oC, and full melt-reprocessability. Considering that extrusion and injection molding is used, the storage modulus achieved in this study is significantly higher than that of vitrimers generated by compression molding, which is commonly used in previous research.

Mechanical and viscoelastic properties of novel resin-infused thermoplastic tri-block copolymer 3D glass fabric composites

The current study investigates the mechanical and viscoelastic properties of a novel acrylic resin-infused thermoplastic (Elium®) tri-block copolymer (Nanostrength®) 3D fibre-reinforced composites (FRCs). The toughened thermoplastic resins with three different concentrations of tri-block copolymer, i.e., 10 wt%, 15 wt%, and 20 wt%, were prepared and used to fabricate thermoplastic 3D-FRCs using a vacuum-assisted resin-infusion process at room temperature. The flexural, interlaminar, and viscoelastic properties and failure modes were evaluated and compared with those of pristine thermoplastic 3D-FRCs. The addition of tri-block copolymer significantly improves the flexural strength of 3D-FRC (up to 75 % and 34 % along the warp and fill directions, respectively, at 15 wt% of tri-block copolymer) and interlaminar shear strength (up to 80 % and 111 % along the warp and fill directions, respectively, at 20 wt% of tri-block copolymer). Additionally, the residual flexure and interlaminar shear strength improved up to 35 % and 109 % at 15 wt% of tri-block copolymer. Dynamic mechanical analysis (DMA) demonstrated that the glass transition temperature and storage modulus of thermoplastic 3D-FRCs were increased up to 11 °C and 24 %, respectively at 20 wt% of tri-block copolymer, which may be due to increased physical crosslinking and the agglomeration of tri-block copolymer particles. The improved mechanical and viscoelastic properties of resin-infused thermoplastic tri-block copolymer 3D-FRCs are attributed to better interface adhesion, improved matrix toughness, and crack-bridging mechanisms induced by the tri-block copolymer. The toughened thermoplastic 3D-FRCs can be utilized in the design and development of composite structures for improved damage tolerance applications.

Volumetric PTV For Fermenting Bread Dough Visualized By Micro X-Ray Computed Tomography

To elucidate the relationship between the formation of internal structures and changes in viscoelastic properties for improving the quality stability of porous and heterogeneous materials, we focused on bread dough that forms an internal bubble structure through yeast metabolism. Specifically, we conducted a time-series measurement of the internal structure and viscoelastic properties during fermentation, particularly in the heterogeneous condition when additives are mixed into the homogeneous dough. We performed a time-lapse imaging using a digital camera to investigate the inflation volume and rate of fermenting bread dough. We used X-ray CT to visualize the internal bubble structure during the fermenting process and evaluated the changes in viscoelastic properties using a dynamic mechanical analysis. The results indicated that the addition of raisins to the bread dough negatively affected its inflation, made the bubble structure of the dough near the raisins larger and coarsened, and altered the viscoelastic properties.

Design and rigid-flexible dynamic analysis of a morphing wing eight-bar mechanism

Design and rigid-flexible dynamic analysis of a morphing wing eight-bar mechanism

Natural Rubber/Styrene-Butadiene Rubber Blend Composites Potentially Applied in Damping Bearings.

Natural rubber (NR) composites have been widely applied in damping products to reduce harmful vibrations, while rubber with only a single composition barely meets performance requirements. In this study, rubber blend composites including various ratios of NR and styrene butadiene rubber (SBR) were prepared via the conventional mechanical blending method. The effects of the rubber components on the compression set, compression fatigue temperature rising and the thermal oxidative aging properties of the NR/SBR blend composites were investigated. Meanwhile, the dynamic mechanical thermal analyzer and rubber processing analyzer were used to characterize the dynamic viscoelasticity of the NR/SBR blend composites. It was shown that, with the increase in the SBR ratio, the vulcanization rate of the composites increased significantly, while the compression fatigue temperature rising of the composites decreased gradually from 47 °C (0% SBR ratio) to 31 °C (50% SBR ratio). The compression set of the composites remained at ~33% when the SBR ratio was no more than 20%, and increased gradually when the SBR ratio was more than 20%.

Nucleation, Development and Healing of Micro-Cracks in Shape Memory Polyurethane Subjected to Subsequent Tension Cycles.

Thermoresponsive shape memory polymers (SMPs) have garnered increasing interest for their exceptional ability to retain a temporary shape and recover the original configuration through temperature changes, making them promising in various applications. The SMP shape change and recovery that happen due to a combination of mechanical loading and appropriate temperatures are related to its particular microstructure. The deformation process leads to the formation and growth of micro-cracks in the SMP structure, whereas the subsequent heating over its glass transition temperature Tg leads to the recovery of its original shape and properties. These processes also affect the SMP microstructure. In addition to the observed macroscopic shape recovery, the healing of micro-crazes and micro-cracks that have nucleated and developed during the loading occurs. Therefore, our study delves into the microscopic aspect, specifically addressing the healing of micro-cracks in the cyclic loading process. The proposed research concerns a thermoplastic polyurethane shape memory polymer (PU-SMP) MM4520 with a Tg of 45 °C. The objective of the study is to investigate the effect of the number of tensile loading-unloading cycles and thermal shape recovery on the evolution of the PU-SMP microstructure. To this end, comprehensive research starting from structural characterization of the initial state and at various stages of the PU-SMP mechanical loading was conducted. Dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS) and scanning electron microscopy (SEM) were used. Moreover, the shape memory behavior in the thermomechanical loading program was investigated. The obtained average shape fixity value was 99%, while the shape recovery was 92%, which confirmed good shape memory properties of the PU-SMP. Our findings reveal that even during a single loading-unloading tension cycle, crazes and cracks nucleate on the surface of the PU-SMP specimen, whereas the subsequent temperature-induced shape recovery process carried out at the temperature above Tg enables the healing of micro-cracks. Interestingly, the surface of the specimen after three and five loading-unloading cycles did not exhibit crazes and cracks, although some traces of cracks were visible. The traces disappeared after exposing the material to heating at Tg + 20 °C (65 °C) for 30 min. The crack closure phenomenon during deformation, even without heating over Tg, occurred within three and five subsequent cycles of loading-unloading. Notably, in the case of eight loading-unloading cycles, cracks appeared on the surface of the PU-SMP and were healed only after thermal recovery at the particular temperature over Tg. Upon reaching a critical number of cycles, the proper amount of energy required for crack propagation was attained, resulting in wide-open cracks on the material's surface. It is worth noting that WAXS analysis did not indicate strong signs of typical highly ordered structures in the PU-SMP specimens in their initial state and after the loading history; however, some orientation after the cyclic deformation was observed.

Various Morphologies of Graphitic Carbon Nitride (g-C3N4) and Their Effect on the Thermomechanical Properties of Thermoset Epoxy Resin Composites.

This research aims to highlight the importance of diverse forms of graphitic carbon nitride (g-C3N4) as strengthening elements in epoxy composites. It explores the influence of three different forms of g-C3N4 and their concentrations on the mechanical properties of the epoxy composites. Various characterization techniques, such as scanning electron microscopy (SEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FTIR), were utilized to comprehend the effects of g-C3N4 morphology and particle size on the physical and chemical characteristics of epoxy resin. Mechanical properties, such as tensile strength, strain, modulus, and fracture toughness, were determined for the composite samples. SEM analysis was performed to examine crack morphology in samples with different reinforcements. Findings indicate that optimal mechanical properties were achieved with a 0.5 wt% bulk g-C3N4 filler, enhancing tensile strength by 14%. SEM micrographs of fracture surfaces revealed a transition from brittle to rough morphology, suggesting increased toughness in the composites. While the TGA results showed no significant impact on degradation temperature, dynamic mechanical analysis demonstrated a 17% increase in glass transition temperature. Furthermore, the improvement in thermal breakdown up to 600 °C was attributed to reinforced covalent bonds between carbon and nitrogen, supported by FTIR results.

Mercerized flax-g-poly(polyvinyl alcohol + acrylic acid) reinforced polyester resin derived from waste plastic bottles: dynamic mechanical analysis and chemical-thermal resistance

Mercerized flax-g-poly(polyvinyl alcohol + acrylic acid) reinforced polyester resin derived from waste plastic bottles: dynamic mechanical analysis and chemical-thermal resistance

Hygrothermal effect and statistical analysis of the interfacial performance of nano and microscale polymer composites

ABSTRACT Hygrothermal exposure significantly impacts polymer composite (PMC) performance, affecting various industries. This study evaluated the short-term hygrothermal effects on PMCs by examining interfacial shear strength (IFSS), water uptake, glass transition temperature (Tg), and morphology. Data-driven techniques minimized experimental time while analyzing multiple factors. Specimens were immersed in water at 25°C and 70°C for 3, 7, and 14 days. The IFSS between carbon nanotube yarns and carbon fiber with epoxy (EPON™ 862) was measured before and after exposure. Statistical analysis indicated that fiber type significantly influenced IFSS, while time had a marginal effect and temperature had no impact. The IFSS decreased by 4.14% for CF/epoxy and 14.9% for CNT/epoxy. Water uptake analysis revealed weight gains of 0.465% and 1.566% for epoxy after 14 days at 25°C and 70°C, respectively. Morphological studies showed moisture penetration between 7 and 14 days. Thermomechanical analysis (TMA) indicated that pristine epoxy expanded by 0.318% of its original height. After 14 days, the Tg of epoxy decreased by 6.4% at 25°C and 9.7% at 70°C. Dynamic mechanical analysis (DMA) on dried epoxy samples showed similar Tg but varied tan delta curves due to plasticization. Short-term hygrothermal evaluation revealed degradation in interface quality and viscoelastic properties.

Thermomechanical Material Characterization of Polyethylene Terephthalate Glycol with 30% Carbon Fiber for Large-Format Additive Manufacturing of Polymer Structures.

Large-format additive manufacturing (LFAM) is used to print large-scale polymer structures. Understanding the thermal and mechanical properties of polymers suitable for large-scale extrusion is needed for design and production capabilities. An in-house-built LFAM printer was used to print polyethylene terephthalate glycol with 30% carbon fiber (PETG CF30%) samples for thermomechanical characterization. Thermogravimetric analysis (TGA) shows that the samples were 30% carbon fiber by weight. X-ray microscopy (XRM) and porosity studies find 25% voids/volume for undried material and 1.63% voids/volume for dry material. Differential scanning calorimetry (DSC) shows a glass transition temperature (Tg) of 66 °C, while dynamic mechanical analysis (DMA) found Tg as 82 °C. The rheology indicated that PETG CF30% is a good printing material at 220-250 °C. Bending experiments show an average of 48.5 MPa for flexure strength, while tensile experiments found an average tensile strength of 25.0 MPa at room temperature. Comparison with 3D-printed PLA and PETG from the literature demonstrated that LFAM-printed PETG CF30% had a comparative high Young's modulus and had similar tensile strength. For design purposes, prints from LFAM should consider both material choice and print parameters, especially when considering large layer heights.

Effect of the Al/Si ratio on intumescent Na-based geopolymer

This research investigates the fire resistance properties of alkali activated Na-based geopolymers (GP), used as steel protective coatings. The effect of different Al/Si molar ratios (0–0.54) is evaluated fire test. When coated on a steel plate, GP having the smaller Al/Si ratio exhibits an intumescent behavior with the highest expansion. When Al/Si = 0, the temperature at the backside of the steel plate is 313 °C which is decreased by 347 °C compared to an uncoated steel plate (660 °C). After fire testing, the GP physico-chemical properties are characterized with optical microscopy, Electron probe micro-analysis, dynamic mechanical analysis. According to stiffness test results, when the temperature approaches 100 °C, the GP with a given Al/Si ratio (different from zero) softens and expands (intumescence). The greater the Al/Si ratio in the GP, the more rigid the structure; this phenomenon limits expansion, and hence, lowers the fire protection.

Fabrication and characterization of PMMA denture base nanocomposite reinforced with hydroxyapatite and multi-walled carbon nanotubes

Polymethyl Methacrylate (PMMA) is still one of the most popular denture base materials in dentistry due to its superior mechanical properties. However, its long-term use can result in defects such as low flexural strength and brittleness, which can be addressed by strengthening its mechanical properties. In this study, the effect of adding non-modified and modified hydroxyapatite nanoparticles (HaP NPs) and multi-walled carbon nanotubes (MWCNTs) on the thermal and mechanical properties of PMMA denture base materials was investigated. First, the modified HaP (MHaP) NPs and modified MWCNTs (MMWCNTs) were prepared by a vinyltriethoxysilane (VTES) agent. Then, two-component PMMA-HaP/MHaP and PMMA-MWCNT/MMWCNT, and three-component PMMA-HaP/MHaP-MWCNT/MMWCNT composite samples were fabricated from commercial dental heat-curing acrylic resin (Acrosun) with different amounts of HaP/MHaP (3, 5, and 10 wt%) and MWCNT/MMWCNT (0.25, 0.5, and 1 wt%). The samples were investigated by Simultaneous Thermal Analysis (STA), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-Ray Spectroscopy (EDS), Dynamic Mechanical Analysis (DMA), and Three-point flexural test. It was observed that surface modification of NPs improved the interaction of NPs and polymer chains in the matrix and resulted in better mechanical properties of nanocomposites. In the sample containing 3 wt% MHaP and 0.25 wt% MMWCNT, the flexural strength and flexural modulus were increased by 45 % and 42 % compared to the control sample, respectively, and the glass transition temperature (Tg) based on the DMA test was 152.7 °C, which was higher than in the other samples. The results of MTT assay studies indicated that adding MHaP and MMWCNT enhanced cell viability. In the PMMA- 3 wt% MHaP- 0.25 wt% MMWCNT composite, the cell viability was increased to 153.75 ± 9.7 % and confirmed its biocompatibility properties.

TDAE aromatic oil preference for polymer blends: An analysis of S-SBR, BR, and miscible S-SBR/BR systems

This study assesses the impact of Treated Distillate Aromatic Extract (TDAE) oil, at concentrations of 0–20 parts per hundred rubber (phr), on the glass transition temperature (Tg) of High Vinyl/Low Styrene Styrene-Butadiene Rubber (HVLSS-SBR), polybutadiene rubber (BR), and their blends with weight ratios of 70/30 and 50/50. Using Dynamic Mechanical Analysis, Broadband Dielectric Spectroscopy, and Positron Annihilation Lifetime Spectroscopy, we found that TDAE modifies Tg and fractional free volume (Fv) differently across materials. In HVLSS-SBR, TDAE reduced Tg by approximately 10 °C and increased Fv by 0.8 %. In BR, TDAE raised Tg by 5–7 °C without altering Fv. The 70/30 blend showed no Tg change but a 0.6 % Fv increase. For the 50/50 blend, one Havriliak-Negami equation indicated a Tg rise of 2–3 °C and a 0.4 % Fv increase. A two-equation analysis revealed a 6 °C Tg increase and 0.9 % Fv boost in the BR-rich phase, versus a 2 °C rise and 0.3 % Fv uptick in the HVLSS-SBR-rich phase. The sequence of compatibility, influenced by TDAE, is crystalline BR > amorphous BR > HVLSS-SBR >70/30 blend >50/50 blend. This study provides valuable insights into the behavior of TDAE oil in rubber blends and can serve as a basis for further research in this field.

Molecular Ball Joints: Mechanochemical Perturbation of Bullvalene Hardy-Cope Rearrangements in Polymer Networks.

The solution-state fluxional behavior of bullvalene has fascinated physical organic and supramolecular chemists alike. Little effort, however, has been put into investigating bullvalene applications in bulk, partially due to difficulties in characterizing such dynamic systems. To address this knowledge gap, we herein probe whether bullvalene Hardy-Cope rearrangements can be mechanically perturbed in bulk polymer networks. We use dynamic mechanical analysis to demonstrate that the activation barrier to the glass transition process is significantly elevated for bullvalene-containing materials relative to "static" control networks. Furthermore, bullvalene rearrangements can be mechanically perturbed at low temperatures in the glassy region; such behavior facilitates energy dissipation (i.e., increased hysteresis energy) and polymer chain alignment to stiffen the material (i.e., increased Young's modulus) under load. Computational simulations corroborate our work that showcases bullvalene as a reversible "low-force" covalent mechanophore in the modulation of viscoelastic behavior.

Advances in mechanical and physicochemical performances of recycled carbon fiber reinforced PEKK composites

In recent years, waste storage and recycling have been important issues. All efforts shown in these fields aim to help resolve concerns related to climate change. In this study, recycled CF/PEKK thermoplastic composite materials were reviewed to reduce the environmental impact of materials during the production phase as well as economic costs and ensure product continuity. Comparisons between unprocessed or virgin material and recycled materials were performed by bending and interlaminar shear strength (ILSS) analyses. In addition to mechanical tests, physicochemical tests such as differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and fiber void ratio (FVC)-porosity tests were conducted. Images of the samples were observed by scanning electron microscopy (SEM) to interpret changes in the structure before and after the recycling. According to the experimental results, it was found that the virgin thermoplastic composite showed 68.05% higher flexural strength and 7.85% higher flexural modulus compared to the recycled thermoplastic composites. The average ILSSs were measured as 81.8 MPa and 64.7 MPa for the virgin and the recycled thermoplastic composites, respectively. Hence, it is obvious that the recycled composites could be used for applications that require less strength and durability. Finally, it was concluded that recyclable materials can be reused in the aero structures.

Hygrothermal effects on the durability of resin‐infused thermoplastic E‐glass fiber‐reinforced composites in marine environment

AbstractThis paper presents a comparative assessment of hygrothermal effects on the mechanical and thermomechanical properties of resin‐infused thermoplastic E‐glass fiber‐reinforced composites (FRC) in the marine environment. The thermoplastic FRCs were immersed in seawater at two different aging temperatures, that is, 35 and 70°C. The quasi‐static tests were conducted on unaged and aged FRCs, followed by scanning electron microscopy (SEM) to determine the effect of the marine environment on the mechanical properties and damage progression. The specimens immersed at 70°C showed a significant drop of 46.7%, 39.7%, 22.6%, and 16% in mechanical properties (tensile, compression, flexural, and ILSS) mainly due to plasticization, matrix cracking, and fiber/matrix debonding. The specimens immersed at 35°C showed a reduction in tensile, compressive, and flexural strength of 10%, 14.7% and 1.9% respectively, with no significant effect on ILSS. In addition, dynamic mechanical analysis (DMA) reveals that prolonged aging induces an increase in glass transition temperature due to polymerization reactions. This work is intended to reveal the effect of extreme marine environment on the resin‐infused thermoplastic FRC and to provide a useful reference for their potential structural applications in the marine industry.Highlights Influence of aging conditions on the long‐term performance of FRCs. Hygrothermal aging leads to an increase in the glass transition temperature. The marine environment degrades mechanical properties of FRCs by up to 50%. Matrix cracking and fiber‐matrix debonding evolved as dominant failure modes.

Crystallization and performance evolution of PHBV nanocomposites through annealing: The role of surface modification of CNCs

To address the brittleness challenge of polyhydroxybutyrate-co-valerate (PHBV) rooting from its slow nucleation rate, cellulose nanocrystals (CNCs) were employed as bio-based nano nucleation and reinforcement agents. CNCs were further functionalized through succinylation using aliphatic dodecyl succinic anhydride (DDSA), for improved compatibility and dispersion within PHBV. Nanocomposites of PHBV incorporating pristine or DDSA-modified CNC (mCNC) were prepared through solution mixing followed by melt injection molding. The study focused on investigating how CNCs and mCNCs affect the crystallization behavior, thermal, rheological, and mechanical properties of PHBV nanocomposites over time, in the course of annealing or conditioning. Thermal results revealed that the incorporation of neat CNCs generally improving stability due to restricted polymer chain mobility and hydrogen bonding, while DDSA-modified CNCs show varied effects depending on the concentration, sometimes diminishing stability due to increased chain mobility. Polarized optical microscopy revealed the superior nucleation efficiency of mCNC, especially at low contents, leading to smaller and numerous spherulites over conditioning. Rheological analysis indicated a dilution effect of the hairy mCNCs, decreasing both dynamic modulus and complex viscosity. Mechanical properties, assessed through tensile testing and dynamic mechanical analysis after 15 days of conditioning, demonstrated the evolving effect of CNCs on aging-induced embrittlement and thermo-mechanical performance of PHBV during storage. The results revealed that incorporating 1 wt% mCNCs effectively toughened PHBV, increasing Young's modulus, and decreasing Tg without scarifying elongation at break compared to neat PHBV. The findings position mCNCs as a promising nucleation agent which retains PHBV nanocomposites toughness after aging.

Fatigue behavior of polymethyl methacrylate/acrylonitrile butadiene styrene blends including blend composition, stress ratio, frequency, and holding pressure effects

In engineering applications, polymer materials are expected to exhibit superior fatigue life and balanced mechanical properties as essential performance criteria. The blending method is an important alternative in improving the performance criteria of ABS polymer in service. Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), and Dynamic Mechanical Analysis (DMA) methods were used for characterization. The effects of the PMMA fraction on the mechanical and fatigue behavior of PMMA/ABS blends were investigated by tensile and fatigue tests. Also, the influence of blend composition, stress amplitudes, stress ratio, holding pressure, and loading frequency on fatigue life is considered. The study improved yield strength, tensile strength, and elongation at break values of blends compared to ABS. In addition, 115 % and 75 % improvements were achieved in fatigue cycles at high and low-stress amplitudes with blends, respectively, for tension/tension loading. Similar improvements were obtained for fully reverse loading at 218 %. Thus, it was determined that the PMMA/ABS blend exhibited superior fatigue life in both tension/tension and fully reverse loading situations. Finally, it has been understood that PMMA/ABS blends can be designed to have mechanical properties and fatigue life behavior that can meet different requirements in conditions for engineering applications.

Correlation analysis of evaluation methods and indicators for low-temperature performance of epoxy asphalt

Selecting an epoxy asphalt (EA) material with excellent low-temperature performance is a challenging task due to that the traditional test methods and indicators for thermoplastic asphalt may not be appropriate for thermosetting EA, and the binders’ low-temperature performance does not always match that of mixtures. The primary purpose of this study is to determine the appropriate low-temperature evaluation methods and indexes of EA materials and the correlation between the low-temperature performance of EA binder and EA mixture (EAM). First, the low-temperature performance of four EA binders was analyzed using tensile, bending beam rheometer (BBR), and dynamic mechanical analysis (DMA) tests. Then, the low-temperature cracking resistance of the EAMs was evaluated through beam bending and semi-circular bend (SCB) tests. Finally, Pearson correlation analysis was performed separately on the low-temperature indicators of EA binders and EAMs. Moreover, the Grey correlation analysis was employed to determine the correlation between the low-temperature properties of the two. The results showed that the correlation between fracture elongation (ε) and other test indicators was not significant. The multiple indicators of the BBR, such as viscoelastic parameters, viscous deformation ratio (JR), along with the glass transition temperature (Tg) of the DMA, showed consistent evaluation results for the low-temperature performance of the four EA binders. However, the correlation of these indicators with the cracking resistance of the EAM was notably different. The flexural strain energy density of the beam bending test and SCB fracture energies demonstrated excellent correlation. The grey correlation analysis results of these two indicators as reference series were highly similar. Specifically, the novel JR in this study and the Tg exhibited a better correlation with the low-temperature cracking resistance of EAM. These two indicators were preferentially recommended for the evaluation of the low-temperature performance of EA and the prediction of the low-temperature cracking resistance of EAM.