scholarly journals Aromatic Hyperbranched Polyester/RTM6 Epoxy Resin for EXTREME Dynamic Loading Aeronautical Applications

Nanomaterials ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 188 ◽  
Author(s):  
Aldobenedetto Zotti ◽  
Ahmed Elmahdy ◽  
Simona Zuppolini ◽  
Anna Borriello ◽  
Patricia Verleysen ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Dynamic Compression ◽  
Condensation Reaction ◽  
Glassy State ◽  
Rate Sensitivity ◽  
Strain Energy Release ◽  
Critical Stress Intensity Factor ◽  
Hyperbranched Polyester ◽  
Compression Tests ◽  
Scanning Calorimetry

The effects of the addition of an aromatic hyperbranched polyester (AHBP) on thermal, mechanical, and fracture toughness properties of a thermosetting resin system were investigated. AHBP filler, synthesized by using a bulk poly-condensation reaction, reveals a glassy state at room temperature. Indeed, according to differential scanning calorimetry measurements, the glass transition temperature (Tg) of AHBP is 95 °C. Three different adduct weight percentages were employed to manufacture the AHBP/epoxy samples, respectively, 0.1, 1, and 5 wt%. Dynamical Mechanical Analysis tests revealed that the addition of AHBP induces a negligible variation in terms of conservative modulus, whereas a slight Tg reduction of about 4 °C was observed at 5 wt% of filler content. Fracture toughness results showed an improvement of both critical stress intensity factor (+18%) and critical strain energy release rate (+83%) by adding 5 wt% of AHBP compared to the neat epoxy matrix. Static and dynamic compression tests covering strain rates ranging from 0.0008 to 1000 s−1 revealed a pronounced strain rate sensitivity for all AHBP/epoxy systems. The AHBP composites all showed an increase of the true peak yield compressive strength with the best improvement associated with the sample with 0.1 wt% of AHBP.

The Study of Epoxy Resins Modified By PPESK

2012 ◽  
Vol 463-464 ◽  
pp. 181-184
Author(s):  
Ya Juan Xu ◽  
Qin Cun Cao ◽  
Xi Gao Jian
Keyword(s):  
Fracture Toughness ◽  
Critical Stress Intensity Factor ◽  
Diglycidyl Ether ◽  
Fracture Mechanisms ◽  
Moderate Increase ◽  
Scanning Calorimetry ◽  
Curing Reaction ◽  
Accelerated Curing ◽  
The Matrix ◽  
Kinetics Of

A series of blends have been prepared by adding a novel thermoplastic poly (phthalazinone ether sulfone ketone) (PPESK) in varying proportions to diglycidyl ether of bisphenol A epoxy resin (DGEBA) cured with p-diaminodiphenylsulfone. The kinetics of curing reaction and glass transition temperature (Tg) of PPESK/DGEBA blends were performed using differential scanning calorimetry (DSC) technique. It is proved that the addition of PPESK accelerated curing reaction and resulted in great enhancement of thermal properties of the blends. There was moderate increase in the fracture toughness as estimated by the critical stress intensity factor (KIc). Compared to that of unmodified epoxy, the maximum toughness of the modified blends had increased 32% by addition of 15 phr PPESK. Fracture mechanisms such as crack deflection and branches, ductile microcracks, ductile tearing of the thermoplastic of the matrix were responsible for the increase in the fracture toughness of the blends

scholarly journals High strain rate compression behaviour of 3D printed Carbon-PA

2021 ◽  
Author(s):  
Mattia Utzeri ◽  
Emanuele Farotti ◽  
Mattia Coccia ◽  
Edoardo Mancini ◽  
Marco Sasso
Keyword(s):  
Strain Rate ◽  
Pulse Shaping ◽  
Dynamic Condition ◽  
Dynamic Compression ◽  
Rate Sensitivity ◽  
Compression Tests ◽  
Fused Filament Fabrication ◽  
Compression Behaviour ◽  
Mechanical Performances ◽  
Printing Direction

Abstract In the last few years, Fused Filament Fabrication is growing in the industrial field for the manufacture of final products by using new materials with high mechanical performances. Among those, one of the strongest is Carbon-PA. This is a composite material made by Nylon thermoplastic matrix filled with short carbon fibers reinforces. The aim of this work is to investigate its mechanical properties in static and dynamic conditions. Cylindrical specimens were produced by extruding the material in the three main printing directions. Then, uniaxial quasi-static and dynamic compression tests have been performed to evaluate its strain rate sensitivity. Dynamic tests have been carried out through a direct Split Hopkinson Bar setup with a pulse-shaping technique. The results show a compression behaviour dependent on the printing direction and strain rate. The behaviour of Carbon-PA was different between static and dynamic condition, passing from ductile to brittle. Moreover, a tomography analysis was carried out on the samples to evaluate the voids distribution. Graphic abstract

Enhancing Fracture Toughness and Stress Energy Release Rate of Vinyl Ester Matrix Using Dual Reinforcement of CNT and GNP

MRS Advances ◽  
2018 ◽  
Vol 3 (15-16) ◽  
pp. 867-873
Author(s):  
Christopher Gapstur ◽  
Hassan Mahfuz ◽  
Javad Hashemi ◽  
Andrew C. Terentis
Keyword(s):  
Fracture Toughness ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Vinyl Ester ◽  
Strain Energy Release ◽  
Decomposition Temperature ◽  
Scanning Calorimetry ◽  
Dsc Studies ◽  
Interface Sliding

ABSTRACTIn this paper, we report a method of increasing fracture toughness (KIC) and strain energy release rate (GIC) of vinyl ester matrix by adopting a dual reinforcement strategy. Reinforcements were carbon nanotubes (CNT) and graphene nanoplatelets (GNP). Both categories of nanoparticles were functionalized with COOH. The idea was to enhance crack bridging and interface sliding with CNT inclusions, given their high aspect ratio. In addition, promote crack-tip blunting and cross-linking density with GNP inclusions, due to their platelet structures. Both KIC and GIC were measured using ASTM D5045-14. An exhaustive experimental study revealed an optimum loading of both nanoparticles to be 0.25 wt% CNT and 0.5 wt% GNP, based on the highest combination of KIC and GIC values. We observed that stress intensity factor, KIC, of neat vinyl ester increased by 43% from 1.14 to 1.62 MPa*(m½). Meanwhile, the improvement in GIC was even greater with an increase of 65%, i.e., from 370 to 610 J/(m2). Differential scanning calorimetry (DSC) studies showed a discernible shift in glass transition temperature (Tg) from 123 to 128°C. The slight temperature increase was similar in thermogravimetric analysis (TGA). We observed the maximum thermal decomposition temperature (Tp) increase from 410 to 414°C, as was evident in the derivative TGA (DTG) curves.

scholarly journals Thermal Properties and Fracture Toughness of Epoxy Nanocomposites Loaded with Hyperbranched-Polymers-Based Core/Shell Nanoparticles

Nanomaterials ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 418 ◽  
Author(s):  
Aldobenedetto Zotti ◽  
Simona Zuppolini ◽  
Anna Borriello ◽  
Mauro Zarrelli
Keyword(s):  
Thermal Stability ◽  
Fracture Toughness ◽  
Thermal Properties ◽  
Strain Energy Release ◽  
Critical Stress Intensity Factor ◽  
Core Shell ◽  
Shell Nanoparticles ◽  
Maximum Increase ◽  
Core Diameter ◽  
Core Shell Nanoparticles

Synthesized silicon oxide (silica) nanoparticles were functionalized with a hyperbranched polymer (HBP) achieving a core/shell nanoparticles (CSNPs) morphology. CSNPs were characterized by Fourier Transform Infrared (FTIR) spectroscopy, Transmission Electron Microscopy (TEM), and Thermogravimetric Analysis (TGA). A core diameter of about 250 nm with a 15 nm thick shell was revealed using TEM images. An aeronautical epoxy resin was loaded with the synthesized CSNPs at different percentages and thermal properties, such as thermal stability and dynamic mechanical properties, were investigated with the use of different techniques. Although the incorporation of 2.5 wt% of CSNPs induces a ~4 °C reduction of the hosting matrix glass transition temperature, a slight increase of the storage modulus of about ~10% was also measured. The Kissinger Method was employed in order to study the thermal stability of the nanocomposites; the degradation activation energies that resulted were higher for the sample loaded with low filler content with a maximum increase of both degradation step energies of about ~77% and ~20%, respectively. Finally, fracture toughness analysis revealed that both the critical stress intensity factor (KIC) and critical strain energy release rate (GIC) increased with the CSNPs content, reporting an increase of about 32% and 74%, respectively, for the higher filler loading.

scholarly journals Roles of Small Polyetherimide Moieties on Thermal Stability and Fracture Toughness of Epoxy Blends

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3310
Author(s):  
Seul-Yi Lee ◽  
Min-Joo Kang ◽  
Seong-Hwang Kim ◽  
Kyong Yop Rhee ◽  
Jong-Hoon Lee ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Fracture Toughness ◽  
Polymer Networks ◽  
Strain Energy Release ◽  
Critical Stress Intensity Factor ◽  
Diglycidyl Ether ◽  
Interpenetrating Polymer Networks ◽  
Test Machine ◽  
Epoxy Blends

Bisphenol A diglycidyl ether (DGEBA) was blended with polyetherimide (PEI) as a thermoplastic toughener for thermal stability and mechanical properties as a function of PEI contents. The thermal stability and mechanical properties were investigated using a thermogravimetric analyzer (TGA) and a universal test machine, respectively. The TGA results indicate that PEI addition enhanced the thermal stability of the epoxy resins in terms of the integral procedural decomposition temperature (IPDT) and pyrolysis activation energy (Et). The IPDT and Et values of the DGEBA/PEI blends containing 2 wt% of PEI increased by 2% and 22%, respectively, compared to those of neat DGEBA. Moreover, the critical stress intensity factor and critical strain energy release rate for the DGEBA/PEI blends containing 2 wt% of PEI increased by 83% and 194%, respectively, compared to those of neat DGEBA. These results demonstrate that PEI plays a key role in enhancing the flexural strength and fracture toughness of epoxy blends. This can be attributed to the newly formed semi-interpenetrating polymer networks (semi-IPNs) composed of the epoxy network and linear PEI.

Epoxy matrix toughness improvement via reactive bio-resin alloying

2016 ◽  
Vol 29 (7) ◽  
pp. 772-784 ◽  
Author(s):  
S Mohajeri ◽  
MJ Zohuriaan-Mehr ◽  
S Pazokifard
Keyword(s):  
Epoxy Matrix ◽  
Furfuryl Alcohol ◽  
Flexural Modulus ◽  
Strain Energy Release ◽  
Cost Effective ◽  
Critical Stress Intensity Factor ◽  
Diglycidyl Ether ◽  
Scanning Calorimetry ◽  
Density Reduction ◽  
Β Relaxation

A facile solvent-less approach to toughen epoxy thermosets by means of a bio-based resin, that is, poly(furfuryl alcohol) (PFA; furan resin) is reported. The bio-resin PFA was firstly synthesized through polycondensation reaction of furfuryl alcohol as a bio-monomer and maleic anhydride as a catalyst. Different amounts of PFA were blended with diglycidyl ether of bisphenol A epoxy resin and cured by diethylenetriamine as a hardener, which simultaneously cross-linked both of the epoxy and PFA resins. The curing process was studied by Furrier transform infrared spectroscopy and differential scanning calorimetry. Scanning electron microscopy of the chemically cured blends revealed no phase separation. It was found remarkable increase in flexural modulus and strength of the neat and modified epoxies with increasing PFA content up to around 15%. Moreover, in comparison with neat epoxy, the epoxy-PFA thermosets showed 60% increase in critical stress intensity factor and 123% increase in critical strain energy release rate. In fact, chemical reaction of PFA-incorporated epoxy could toughen the epoxy matrix without sacrificing the flexural strength and modulus. Toughening was obtained through cross-link density reduction. As exhibited by dynamic mechanical thermal analysis, Tan δ and magnitude of β-relaxation were also increased for the epoxy-PFA alloys. Overall, this green, simple, concise and cost-effective approach was suggested for being considered to produce toughened epoxy thermosets in industrial scale.

Effect of Strain Rate on Compressive Behavior of a ZrCuNiAl Bulk Metallic Glass at Room Temperature

2021 ◽  
Vol 1016 ◽  
pp. 1569-1575
Author(s):  
Zhi Ping Guo ◽  
Chuan Ting Wang ◽  
Yong He ◽  
Yuan He ◽  
Lei Guo ◽  
...  
Keyword(s):  
Metallic Glass ◽  
Strain Rate ◽  
Bulk Metallic Glass ◽  
Temperature Rise ◽  
Room Temperature ◽  
Dynamic Compression ◽  
Rate Sensitivity ◽  
Compression Tests ◽  
Compressive Behavior ◽  
Negative Strain Rate Sensitivity

In this study, quasi-static and dynamic compression tests were performed on a ZrCuNiAl bulk metallic glass. The results demonstrated that the ZrCuNiAl bulk metallic glass changed from plastic deformation without strain rate effect to brittle fracture with negative strain rate sensitivity. The fracture surface morphology was related to the strain rate and temperature rise. The modified cooperative-shear model was determined to describe the effect of strain rate and temperature rise on the yield stress of ZrCuNiAl bulk metallic glass.

scholarly journals Physical Aging Behavior of a Glassy Polyether

Polymers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 954
Author(s):  
Xavier Monnier ◽  
Sara Marina ◽  
Xabier Lopez de Pariza ◽  
Haritz Sardón ◽  
Jaime Martin ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Physical Aging ◽  
Glassy State ◽  
Aging Behavior ◽  
Scanning Calorimetry ◽  
Narrow Temperature Range ◽  
Glass Forming ◽  
Fast Scanning Calorimetry

The present work aims to provide insights on recent findings indicating the presence of multiple equilibration mechanisms in physical aging of glasses. To this aim, we have investigated a glass forming polyether, poly(1-4 cyclohexane di-methanol) (PCDM), by following the evolution of the enthalpic state during physical aging by fast scanning calorimetry (FSC). The main results of our study indicate that physical aging persists at temperatures way below the glass transition temperature and, in a narrow temperature range, is characterized by a two steps evolution of the enthalpic state. Altogether, our results indicate that the simple old-standing view of physical aging as triggered by the α relaxation does not hold true when aging is carried out deep in the glassy state.

The rheological behaviour and thermal ageing characteristics of PP/MWCNT/glass fibre multiscale composites

2021 ◽  
pp. 096739112199290
Author(s):  
N Rasana ◽  
K Jayanarayanan ◽  
Krishna Prasad Rajan ◽  
Aravinthan Gopanna
Keyword(s):  
Hybrid Composites ◽  
Rheological Behaviour ◽  
Strain Energy Release ◽  
Critical Stress Intensity Factor ◽  
Thermal Ageing ◽  
Multiwalled Carbon ◽  
Weight Percentage ◽  
Fixed Weight ◽  
Multiscale Composite ◽  
The Matrix

Multiscale hybrid composites were prepared using varying weight percentages (0 to 5) of multiwalled carbon nanotubes (MWCNTs) as nanofiller and a fixed weight percentage (20) of short glass fibres as micro filler (in polypropylene (PP) matrix. The shear and extensional viscosity of the composites was measured using a capillary rheometer. It was observed that even at higher shear rates the synergism of micro and nanofillers in the matrix significantly enhanced the melt viscosity. The complex nanotube network entanglement with micro fillers and PP chains imparted restrictions to the polymer chain movements. The prepared samples were subjected to thermal ageing at 100°C for 4 days in hot air oven. After ageing, multiscale composite with 3 wt% MWCNTs exhibited 28.57% enhancement in strain at break, whereas the tensile strength and modulus reduced by 6.8% and 8% respectively. The fracture toughness properties like strain energy release rate and critical stress intensity factor were not affected for multiscale composite at the optimum content of 3 wt% MWCNT, even after thermal ageing.

scholarly journals Influence of artificial aging: mechanical and physicochemical properties of dental composites under static and dynamic compression

2021 ◽  
Author(s):  
D. C. Gornig ◽  
R. Maletz ◽  
P. Ottl ◽  
M. Warkentin
Keyword(s):  
Mechanical Properties ◽  
Water Sorption ◽  
Artificial Aging ◽  
Filler Content ◽  
Dynamic Compression ◽  
The Other ◽  
Chemical Degradation ◽  
Dental Composites ◽  
Compression Tests ◽  
Acid Ph

Abstract Objective The aim of the study was to evaluate the influence of filler content, degradation media and time on the mechanical properties of different dental composites after in vitro aging. Materials and Methods Specimens (1 mm3) of three commercially available composites (GrandioSO®, Arabesk Top®, Arabesk Flow®) with respect to their filler content were stored in artificial aging media: artificial saliva, ethanol (60%), lactic acid (pH 5) and citric acid (pH 5). Parameters (Vickers microhardness, compressive strength, elastic modulus, water sorption and solubility) were determined in their initial state (control group, n = 3 for microhardness, n = 5 for the other parameters) and after 14, 30, 90 and 180 days (n = 3 for microhardness, n = 5 for the other parameters for each composite group, time point and media). Specimens were also characterized with dynamic-mechanical-thermal analysis (compression tests, F =  ± 7 N; f = 0.5 Hz, 1 Hz and 3.3 Hz; t = 0–170 °C). Results Incorporation of fillers with more than 80 w% leads to significantly better mechanical properties under static and dynamic compression tests and a better water sorption behavior, even after chemical degradation. The influence of degradation media and time is of subordinate importance for chemical degradation. Conclusion Although the investigated composites have a similar matrix, they showed different degradation behavior. Since dentine and enamel occur only in small layer thickness, a test specimen geometry with very small dimensions is recommended for direct comparison. Moreover, the use of compression tests to determine the mechanical parameters for the development of structure-compatible and functionally adapted composites makes sense as an additional standard. Clinical relevance Preferential use of highly filled composites for occlusal fillings is recommended.

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