Tough Hydrogels with Dynamic H-Bonds: Structural Heterogeneities and Mechanical Performances

In this study, coir fibers were successfully modified with henna (derived from the Lawsonia inermis plant) using a high-energy ball-milling process. In the next step, such developed filler was used as a reinforcing filler in the production of rigid polyurethane (PUR) foams. The impact of 1, 2, and 5 wt % of coir-fiber filler on structural and physico-mechanical properties was evaluated. Among all modified series of PUR composites, the greatest improvement in physico-mechanical performances was observed for PUR composites reinforced with 1 wt % of the coir-fiber filler. For example, on the addition of 1 wt % of coir-fiber filler, the compression strength was improved by 23%, while the flexural strength increased by 9%. Similar dependence was observed in the case of dynamic-mechanical properties—on the addition of 1 wt % of the filler, the value of glass transition temperature increased from 149 °C to 178 °C, while the value of storage modulus increased by ~80%. It was found that PUR composites reinforced with coir-fiber filler were characterized by better mechanical performances after the UV-aging.

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Water-Tree Resistant Characteristics of Crosslinker-Modified-SiO2/XLPE Nanocomposites

Materials ◽

10.3390/ma14061398 ◽

2021 ◽

Vol 14 (6) ◽

pp. 1398

Author(s):

Yong-Qi Zhang ◽

Xuan Wang ◽

Ping-Lan Yu ◽

Wei-Feng Sun

Keyword(s):

Electric Fields ◽

Tree Growth ◽

Mechanical Analysis ◽

Water Molecules ◽

Crosslinking Degree ◽

Water Tree ◽

Tree Resistance ◽

Alternating Electric Fields ◽

Trimethylolpropane Triacrylate ◽

Mechanical Performances

Trimethylolpropane triacrylate (TMPTA) as a photoactive crosslinker is grafted onto hydrophobic nanosilica surface through click chemical reactions of mercapto double bonds to prepare the functionalized nanoparticles (TMPTA-s-SiO2), which are used to develop TMPTA-s-SiO2/XLPE nanocomposites with improvements in mechanical strength and electrical resistance. The expedited aging experiments of water-tree growth are performed with a water-knife electrode and analyzed in consistence with the mechanical performances evaluated by means of dynamic thermo-mechanical analysis (DMA) and tensile stress–strain characteristics. Due to the dense cross-linking network of polyethylene molecular chains formed on the TMPTA-modified surfaces of SiO2 nanofillers, TMPTA-s-SiO2 nanofillers are chemically introduced into XLPE matrix to acquire higher crosslinking degree and connection strength in the amorphous regions between polyethylene lamellae, accounting for the higher water-tree resistance and ameliorated mechanical performances, compared with pure XLPE and neat-SiO2/XLPE nanocomposite. Hydrophilic TMPTA molecules grafted on the nano-SiO2 surface can inhibit the condensation of water molecules into water micro-beads at insulation defects, thus attenuating the damage of water micro-beads to polyethylene configurations under alternating electric fields and thus restricting water-tree growth in amorphous regions. The intensified interfaces between TMPTA-s-SiO2 nanofillers and XLPE matrix limit the segment motions of polyethylene molecular chains and resist the diffusion of water molecules in XLPE amorphous regions, which further contributes to the excellent water-tree resistance of TMPTA-s-SiO2/XLPE nanocomposites.

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Numerical and analytical study on the mechanical properties of a connector with long-fiber and metal laminated bolts for prefabricated construction

Advances in Structural Engineering ◽

10.1177/13694332211007377 ◽

2021 ◽

pp. 136943322110073

Author(s):

Xiaoming Zhang ◽

Danni Ren ◽

Xin Liu ◽

Sujun Guan ◽

Xindi Yu ◽

...

Keyword(s):

Energy Dissipation ◽

Analytical Study ◽

High Strength ◽

Bilinear Model ◽

Fiber Layer ◽

Rotational Displacement ◽

Length Direction ◽

Plastic Phase ◽

Fiber Metal ◽

Mechanical Performances

To improve the mechanical performances of joints in prefabricated construction, a type of connection structure with long-fiber and metal laminated bolts (referred to as a fiber-metal connector) is proposed and investigated by simulation and theoretical methods. The results include the following: (1) The fiber layer in bolts can form a second stiffness during rotation. This mechanical characteristic improves the bearing capacities and energy dissipation ability of the connector relative to the conventional metal connector, which are expected to effectively limit the elastoplastic rotational displacement of a structure. (2) For the reason, the fiber layer can bear load in the plastic phase due to its high-strength characteristic in the length direction. (3) A bilinear model for the bearing curve of the fiber-metal connector is proposed, and equations for optimization of fiber layer thickness are obtained with a target on bearing capacity and energy dissipation ability which are approximately higher 30% and 13% than that of the conventional metal connector, respectively. This research is expected to provide a theoretical basis for the application of this fiber-metal connector in engineering and improve the safety of prefabricated structures.

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Molecular-Level Investigation of Cycloaliphatic Epoxidised Ionic Liquids as a New Generation of Monomers for Versatile Poly(Ionic Liquids)

Polymers ◽

10.3390/polym13091512 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1512

Author(s):

Baris Demir ◽

Gabriel Perli ◽

Kit-ying Chan ◽

Jannick Duchet-Rumeau ◽

Sébastien Livi

Keyword(s):

Ionic Liquids ◽

Molecular Level ◽

Computational Approach ◽

Polymer Materials ◽

Chemical Structures ◽

Cycloaliphatic Epoxy ◽

Polymer Models ◽

Mechanical Performances ◽

Dynamics Simulations ◽

New Generation

Recently, a new generation of polymerised ionic liquids with high thermal stability and good mechanical performances has been designed through novel and versatile cycloaliphatic epoxy-functionalised ionic liquids (CEILs). From these first promising results and unexplored chemical structures in terms of final properties of the PILs, a computational approach based on molecular dynamics simulations has been developed to generate polymer models and predict the thermo–mechanical properties (e.g., glass transition temperature and Young’s modulus) of experimentally investigated CEILs for producing multi-functional polymer materials. Here, a completely reproducible and reliable computational protocol is provided to design, test and tune poly(ionic liquids) based on epoxidised ionic liquid monomers for future multi-functional thermoset polymers.

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Effect of Geometric Parameters and Moisture Content on the Mechanical Performances of 3D-Printed Isogrid Structures in Short Carbon Fiber-Reinforced Polyamide

Journal of Materials Engineering and Performance ◽

10.1007/s11665-021-05659-7 ◽

2021 ◽

Author(s):

Valerio Di Pompeo ◽

Archimede Forcellese ◽

Tommaso Mancia ◽

Michela Simoncini ◽

Alessio Vita

Keyword(s):

Carbon Fiber ◽

Moisture Content ◽

Geometric Parameters ◽

Fiber Reinforced ◽

Compression Tests ◽

Short Carbon Fiber ◽

3D Printed ◽

Carbon Fiber Reinforced ◽

Mechanical Performances ◽

Short Carbon

AbstractThe present paper aims at studying the effect of geometric parameters and moisture content on the mechanical performances of 3D-printed isogrid structures in short carbon fiber-reinforced polyamide (namely Carbon PA). Four different geometric isogrid configurations were manufactured, both in the undried and dried condition. The dried isogrid structures were obtained by removing the moisture from the samples through a heating at 120 °C for 4 h. To measure the quantity of removed moisture, samples were weighted before and after the drying process. Tensile tests on standard specimens and buckling tests on isogrid panels were performed. Undried samples were tested immediately after 3D printing. It was observed that the dried samples are characterized by both Young modulus and ultimate tensile strength values higher than those provided by the undried samples. Similar results were obtained by the compression tests since, for a given geometric isogrid configuration, an increase in the maximum load of the dried structure was detected as compared to the undried one. Such discrepancy tends to increase as the structure with the lowest thickness value investigated is considered. Finally, scanning electron microscopy was carried out in order to analyze the fractured samples and to obtain high magnification three-dimensional topography of fractured surfaces after testing.

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Development and analysis of composite overwrapped pressure vessels for hydrogen storage

Journal of Composite Materials ◽

10.1177/00219983211033568 ◽

2021 ◽

pp. 002199832110335

Author(s):

Osman Kartav ◽

Serkan Kangal ◽

Kutay Yücetürk ◽

Metin Tanoğlu ◽

Engin Aktaş ◽

...

Keyword(s):

Hydrogen Storage ◽

Damage Model ◽

Pressure Vessels ◽

Filament Winding ◽

Burst Pressure ◽

Fe Model ◽

Fe Method ◽

Liner Material ◽

Mechanical Performances ◽

Metallic Liner

In this study, composite overwrapped pressure vessels (COPVs) for high-pressure hydrogen storage were designed, modeled by finite element (FE) method, manufactured by filament winding technique and tested for burst pressure. Aluminum 6061-T6 was selected as a metallic liner material. Epoxy impregnated carbon filaments were overwrapped over the liner with a winding angle of ±14° to obtain fully overwrapped composite reinforced vessels with non-identical front and back dome layers. The COPVs were loaded with increasing internal pressure up to the burst pressure level. During loading, deformation of the vessels was measured locally with strain gauges. The mechanical performances of COPVs designed with various number of helical, hoop and doily layers were investigated by both experimental and numerical methods. In numerical method, FE analysis containing a simple progressive damage model available in ANSYS software package for the composite section was performed. The results revealed that the FE model provides a good correlation as compared to experimental strain results for the developed COPVs. The burst pressure test results showed that integration of doily layers to the filament winding process resulted with an improvement of the COPVs performance.

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