Effects of thermal cycling on phenylethynyl-terminated PMDA-type asymmetric polyimide composites

2018 ◽  
Vol 31 (7) ◽  
pp. 861-871
Author(s):  
Yixiang Zhang ◽  
Masahiko Miyauchi ◽  
Steven Nutt
Keyword(s):  
Thermal Cycling ◽  
Mechanical Degradation ◽  
Thermal Cycles ◽  
Oxidative Aging ◽  
Short Beam ◽  
Beam Shear ◽  
Thermally Driven ◽  
The Matrix ◽  
Service Environments ◽  
Thermal Oxidative Aging

The effects of thermal cycling on a polymerized monomeric reactant (PMR) type polyimide (TriA X) reinforced with carbon fibers were investigated. Composite specimens were subjected to 2000 thermal cycles between −54°C and 232°C. At 400-cycle intervals, laminates were inspected for microcracks, and glass transition temperature ( T g) and short-beam shear (SBS) strength were measured. The composites did not exhibit microcracks after thermal cycling, although after 2000 thermal cycles, mechanical properties of the matrix declined slightly. The matrix degradation decreased the resistance to microcracking upon further loading. No effects of thermal oxidative aging were observed from thermal cycling, and thermally driven fatigue and creep were identified as the primary and secondary factors inducing mechanical degradation of the matrix. T g of the composites exhibited no change after 2000 cycles, while the SBS strength decreased slightly (3–9%). The results highlight the potential for use of TriA X composites as long-term structural components in high-temperature service environments.

Experimental Characterization of Matrix Cracking Behavior in Thermally Cycled CFRP Laminates

2002 ◽  
Vol 11 (3) ◽  
pp. 287-305 ◽  
Author(s):  
Shinji Ogihara ◽  
Akira Kobayashi ◽  
Takamoto Ishiguro ◽  
Nobuo Otani
Keyword(s):  
Thermal Cycling ◽  
Crack Density ◽  
Tensile Loading ◽  
Matrix Crack ◽  
Matrix Cracking ◽  
Thermal Cycles ◽  
Critical Energy Release Rate ◽  
Cracking Behavior ◽  
Cfrp Laminates ◽  
The Matrix

The effect of thermal cycling on the mechanical properties of composite materials is an important issue in engineering, especially in their applications to the space environment. The present study concerned with the experimental study of both the thermal cycling induced matrix cracking and the effect of thermal cycling on the matrix cracking behavior under tensile loading in CFRP laminates. Two kinds of carbon/epoxy systems, T800H/3631 and T300/2500, are used for the laminate configurations of (0/90)s and (90/0)s. The specimens are thermally cycled between −196 and 100°C. Thermal cycling tests are performed up to 1000 cycles. The polished edge surfaces of specimens are examined by the replica technique, and then the matrix crack density is measured as a function of the number of thermal cycles. It is found that the first matrix cracking in (0/90)s and (90/0)s laminates occurs at almost the same numbers of thermal cycles. It is also found that the matrix crack density increases more rapidly in (0/90)s laminates than in (90/0)s laminates in both material systems. To investigate the effect of thermal cycling on matrix cracking behavior under tensile loading, a series of tensile tests on thermally cycled specimens are performed. The effect of thermal cycling on matrix cracking under tension is evaluated in terms of the change in the critical energy release rate and the critical stress for matrix cracking.

Mechanical properties of unidirectional aligned bagasse fibers/vinyl ester composite

2016 ◽  
Vol 36 (2) ◽  
pp. 157-163 ◽  
Author(s):  
Ayyanar Athijayamani ◽  
Balasubramaniam Stalin ◽  
Susaiyappan Sidhardhan ◽  
Azeez Batcha Alavudeen
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Impact Strength ◽  
Vinyl Ester ◽  
Flexural Modulus ◽  
Tensile Modulus ◽  
Short Beam ◽  
Beam Shear ◽  
The Matrix ◽  
The Impact

Abstract The present study describes the preparation of aligned unidirectional bagasse fiber-reinforced vinyl ester (BFRVE) composites and their mechanical properties such as tensile, flexural, shear and impact strength. Composites were prepared by a hand lay-up technique developed in our laboratory with the help of a hot press. Mechanical properties were obtained for different fiber contents by varying the number of layers. The obtained tensile property values were compared with the theoretical results. The results show that the tensile strength increased linearly up to 44 wt% and then dropped. However, the tensile modulus increased linearly from 17 wt% to 60 wt%. In the case of flexural properties, the flexural strength increased up to 53 wt% and started to decrease. However, the flexural modulus also increased linearly up to 60 wt%. The impact strength values were higher than the matrix materials for all the specimens. The short beam shear strength values were also increased up to 53 wt% and then dropped. The modified Bowyer and Bader (MBB) model followed by the Hirsch model shows a very good agreement with experimental results in both tensile strength and modulus.

scholarly journals Coupled Hygro-Mechanical Finite Element Method on Determination of the Interlaminar Shear Modulus of Glass Fiber-Reinforced Polymer Laminates in Bridge Decks under Hygrothermal Aging Effects

Polymers ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 845 ◽  
Author(s):  
Xu Jiang ◽  
Chengwei Luo ◽  
Xuhong Qiang ◽  
Qilin Zhang ◽  
Henk Kolstein ◽  
...  
Keyword(s):  
Moisture Absorption ◽  
Mechanical Degradation ◽  
Aging Effects ◽  
Shear Properties ◽  
Desorption Process ◽  
Glass Fiber Reinforced ◽  
Short Beam ◽  
Beam Shear ◽  
Interlaminar Shear ◽  
Interlaminar Shear Modulus

To investigate the mechanical degradation of the shear properties of glass fiber-reinforced polymer (GFRP) laminates in bridge decks under hygrothermal aging effects, short-beam shear tests were performed following the ASTM test standard (ASTM D790-10A). Based on the coupled hygro-mechanical finite element (FE) analysis method, an inverse parameter identification approach based on short-beam shear tests was developed and then employed to determine the environment-dependent interlaminar shear modulus of GFRP laminates. Subsequently, the shear strength and modulus of dry (0% Mt/M∞), moisture unsaturated (30% Mt/M∞ and 50% Mt/M∞), and moisture saturated (100% Mt/M∞) specimens at test temperatures of both 20 °C and 40 °C were compared. One cycle of the moisture absorption–desorption process was also investigated to address how the moisture-induced residual damage degrades the shear properties of GFRP laminates. The results revealed that the shear strength and modulus of moisture-saturated GFRP laminates decreased significantly, and the elevated testing temperature (40 °C) aggravated moisture-induced mechanical degradation. Moreover, an unrecoverable loss of shear properties for the GFRP laminates enduring one cycle of the moisture absorption–desorption process was evident.

Mechanical degradation of carbon fiber/vinyl ester samples subject to marine environments

2021 ◽  
pp. 002199832110050
Author(s):  
Ilaria Papa ◽  
Antonio Formisano ◽  
Valentina Lopresto ◽  
Pietro Russo
Keyword(s):  
Carbon Fiber ◽  
Vinyl Ester ◽  
Low Velocity Impact ◽  
Mechanical Degradation ◽  
Low Velocity ◽  
Saline Environment ◽  
Short Beam ◽  
Before And After ◽  
Beam Shear ◽  
Water Saturated

The paper deals with the mechanical degradation of composite material components in seawater at room temperature. In particular, this study compares quasi-static and dynamic behaviour of carbon fiber/vinyl ester components, dry and water saturated in a saline environment at 3% to simulate the seawater exposition. At this regard, short-beam shear, flexural and low-velocity impact tests were systematically performed before and after the conditioning of the material under examination. Finally, the damage of the impacted specimens was carefully analyzed by visual inspections and ultrasound investigations. Despite a very low water absorption, the analyses allow to highlight different phenomena, reflecting on variations in the mechanical properties and in the extent of the damage of the investigated samples.

Thermo-oxidative aging and thermal cycling of PETI-340M composites

2021 ◽  
pp. 095400832110337
Author(s):  
Xiaochen Li ◽  
Bo Cheng Jin ◽  
Thomas K Tsotsis ◽  
Steven Nutt
Keyword(s):  
High Temperature ◽  
Thermal Cycling ◽  
Mechanical Performance ◽  
Strength Loss ◽  
Mechanical Degradation ◽  
Aging Effects ◽  
Oxidative Aging ◽  
Structural Applications ◽  
Polyimide Composites ◽  
Temperature Aging

Polyimide composites (PETI-340M) were fabricated and subjected to high-temperature aging and thermal cycling to evaluate resistance to degradation. Mechanical-degradation mechanisms and kinetics depended on aging temperature. Aging at 232°C resulted in strength loss due to polymer degradation, while intra-tow cracking was the dominant mechanism during aging at 288°C. Composite panels subjected to thermal-cycling fatigue (−54°C to 232°C) retained mechanical properties without microcracking. However, in regions containing pre-existing fabrication-induced defects (primarily voids), intra-tow microcracks were observed after thermal cycling. Unlike some polyimide composites (PMR-15), oxidative aging effects during thermal cycling were negligible. The thermo-oxidative stability and the retention of mechanical performance after thermal cycling indicates potential for long-term, high-temperature structural applications.

scholarly journals TECHNOLOGICAL ASPECT OF PRODUCTION AND USE OF OIL-OLIGOMERIC ADDITIVE ON BASIS OF SECONDARY OLIGOMERS IN PRODUCTION OF EMULSION RUBBER

2018 ◽  
Vol 61 (4-5) ◽  
pp. 105
Author(s):  
Inna N. Pugacheva ◽  
Nadezhda S. Nikulina ◽  
Sergey S. Nikulin
Keyword(s):  
Rubber Matrix ◽  
Technological Aspect ◽  
Mass Ratio ◽  
Environmental Friendliness ◽  
Oxidative Aging ◽  
The Matrix ◽  
The Stability ◽  
Oxidative Effects ◽  
Thermal Oxidative Aging ◽  
By Products

The paper shows the perspective direction of using by-products and wastes of the petrochemical industry in the production of rubber products. It was revealed that oligomers synthesized from petrochemical by-products can be used as promising additives. The technological aspects of the use of additives based on PN-6 oil and its combination with an oligomer synthesized from by-products of polybutadiene production in the technology of obtaining filled emulsion rubbers were studied. It has been found that the best way to combine oligomeric additives with the matrix of synthetic rubbers is to introduce them into latex in the form of dispersions. The influence of coagulants of different nature on the process of emulsion rubber release filled with oil oligomeric anthioxidant dispersion was investigated. It was found that the change in the mass ratio of oil-oligomeric-anthioxidant dispersion components did not significantly affect the consumption of the coagulant used. It has been shown that the introduction of an oil-oligomeric-anthioxidant additive into the elastomeric compositions at the stage of their creation provides an even distribution of the components in the rubber matrix. The effect of manufactured additives on the properties of the resulting composites was estimated. It has been found that vulcanizates obtained on the basis of rubber with a high content of oligomeric component in the composition of the additive have a higher resistance to thermal oxidative aging. Increasing the stability of vulcanizates to the thermal and oxidative effects indicates a decrease in the losses of the antioxidant in the process of obtaining rubbers and elastomeric compositions. It is shown that the introduction of oily oligomerically antioxidant dispersion in latex at the stage of creation of elastomeric compositions makes it possible to improve the technical and economic efficiency and environmental friendliness of their production. Evaluation of the effect of manufactured oligomeric additives on the properties of the resulting composites revealed their multifunctionality.Forcitation:Pugacheva I.N., Nikulina N.S., Nikulin S.S. Technological aspect of production and use of oil-oligomeric additive on basis of secondary oligomers in production of emulsion rubber. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 4-5. P. 105-110

scholarly journals In-Situ Measurement of Power Loss for Crystalline Silicon Modules Undergoing Thermal Cycling and Mechanical Loading Stress Testing

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 72
Author(s):  
Sergiu Spataru ◽  
Peter Hacke ◽  
Dezso Sera
Keyword(s):  
Thermal Cycling ◽  
Power Loss ◽  
Stress Testing ◽  
Series Resistance ◽  
Short Circuit ◽  
In Situ Measurement ◽  
Mechanical Degradation ◽  
Model Parameters ◽  
The Impact

An in-situ method is proposed for monitoring and estimating the power degradation of mc-Si photovoltaic (PV) modules undergoing thermo-mechanical degradation tests that primarily manifest through cell cracking, such as mechanical load tests, thermal cycling and humidity freeze tests. The method is based on in-situ measurement of the module’s dark current-voltage (I-V) characteristic curve during the stress test, as well as initial and final module flash testing on a Sun simulator. The method uses superposition of the dark I-V curve with final flash test module short-circuit current to account for shunt and junction recombination losses, as well as series resistance estimation from the in-situ measured dark I-Vs and final flash test measurements. The method is developed based on mc-Si standard modules undergoing several stages of thermo-mechanical stress testing and degradation, for which we investigate the impact of the degradation on the modules light I-V curve parameters, and equivalent solar cell model parameters. Experimental validation of the method on the modules tested shows good agreement between the in-situ estimated power degradation and the flash test measured power loss of the modules, of up to 4.31 % error (RMSE), as the modules experience primarily junction defect recombination and increased series resistance losses. However, the application of the method will be limited for modules experiencing extensive photo-current degradation or delamination, which are not well reflected in the dark I-V characteristic of the PV module.

scholarly journals Simultaneous effects of rice husk silica and silicon carbide whiskers on the mechanical properties and morphology of sodium geopolymer

2020 ◽  
Vol 54 (29) ◽  
pp. 4611-4620 ◽  
Author(s):  
Akm Samsur Rahman ◽  
Chirag Shah ◽  
Nikhil Gupta
Keyword(s):  
Silicon Carbide ◽  
Compressive Strength ◽  
Flexural Strength ◽  
Silica Nanoparticles ◽  
Rice Husk ◽  
Silicon Carbide Whiskers ◽  
Short Beam ◽  
Spherical Silica ◽  
Beam Shear ◽  
Strength Improvement

The current research is focused on developing a geopolymer binder using rice husk ash–derived silica nanoparticles. Four types of rice husks were collected directly from various rice fields of Bangladesh in order to evaluate the pozzolanic activity and compatibility of the derived rice husk ashes with precursors of sodium-based geopolymers. Silicon carbide whiskers were introduced into sodium-based geopolymers in order to evaluate the response of silicon carbide whiskers to the interfacial bonding and strength of sodium-based geopolymers along with rice husk ashes. Compression, flexural and short beam shear tests were performed to investigate the synergistic effect of rice husk ashes–derived silica and commercially available silicon carbide whiskers. Results show that rice husk ashes–derived spherical silica nanoparticles reduced nano-porosity of the geopolymers by ∼20% and doubled the compressive strength. The simultaneous additions of rice husk ashes and silicon carbide whiskers resulted in flexural strength improvement by ∼27% and ∼97%, respectively. The increase in compressive strength due to the inclusion of silica nanoparticles is related to the reduction in porosity. The increase in flexural strength due to simultaneous inclusion of silica and silicon carbide whiskers suggest that silica particles are compatible with the metakaolin-based geopolymers, which is effective in consolidation. Finally, microscopy suggest that silicon carbide whiskers are effective in increasing bridged network and crack resistance.

Effect of hybrid thermal cycling and shock on flexural properties of nanoclay/glass/epoxy nanocomposites

2021 ◽  
pp. 096739112110132
Author(s):  
A Bayat ◽  
M Damircheli ◽  
M Esmkhani
Keyword(s):  
Flexural Strength ◽  
Thermal Cycling ◽  
Epoxy Composites ◽  
Flexural Properties ◽  
Flexural Stiffness ◽  
Thermal Cycles ◽  
Epoxy Nanocomposites ◽  
Static Conditions

In present research, the flexural properties of glass/epoxy composites reinforced by nanoclay particles (3, 5 and 7 wt.%) under various hybrid thermal cycling and shock loadings (15 and 30 thermal cycles at immediate −70°C and +100°C temperatures) have been investigated. It was found that the flexural strength of 5 wt.% nanoclay/glass/epoxy nanocomposites under 15 and 30 hybrid thermal loadings was enhanced by 19.35% and 20.78%, respectively. Also, after 15 hybrid thermal loadings, the flexural stiffness of 5 wt.% clay/glass/epoxy nanocomposites increased by 9.30% compared to static conditions. More importantly, after 30 hybrid thermal loadings, by adding more filler contents, the flexural stiffness was increased. For instance, at 7 wt.% clay/glass/epoxy nanocomposites, the flexural stiffness enhanced 17.97% compared to neat composite. FESEM morphology images confirmed that presence of optimum filler contents changed the composites inherent properties. Therefore, the outcome of this research can show various remarkable advantages for researchers to apply nanoclay as nanofillers to reinforce composites structures under hybrid thermal cycling and shock applications.

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