scholarly journals Why is Mechanical Fatigue Different from Toughness in Elastomers? The Role of Damage by Polymer Chain Scission

2021 ◽  
Author(s):  
Gabriel Sanoja ◽  
Xavier P. Morelle ◽  
Jean Comtet ◽  
C. Joshua Yeh ◽  
Matteo Ciccotti ◽  
...  
Keyword(s):  
Applied Load ◽  
Areal Density ◽  
Chain Scission ◽  
Fracture Mechanisms ◽  
Environmental Footprint ◽  
Double Network ◽  
Mechanical Fatigue ◽  
Bond Scission ◽  
Mechanical Durability

<p>Although elastomers often experience 10-100 million cycles prior to failure, there is currently a limited understanding of their resistance to fatigue crack propagation. We use soft and tough double-network elastomers tagged with mechanofluorescent probes to understand the role of damage by sacrificial bond scission on their mechanical durability and fracture toughness. Damage accumulation and localization ahead of the crack tip depend on the areal density of sacrificial bonds, as well as on the applied load (<i>i.e.</i>, cyclic or monotonic). This information serves to engineer fatigue resistant elastomers, understand fracture mechanisms, and reduce the environmental footprint of the polymer industry.</p>

scholarly journals Why is Mechanical Fatigue Different from Toughness in Elastomers? The Role of Damage by Polymer Chain Scission

2021 ◽  
Author(s):  
Gabriel Sanoja ◽  
Xavier P. Morelle ◽  
Jean Comtet ◽  
C. Joshua Yeh ◽  
Matteo Ciccotti ◽  
...  
Keyword(s):  
Applied Load ◽  
Areal Density ◽  
Chain Scission ◽  
Fracture Mechanisms ◽  
Environmental Footprint ◽  
Double Network ◽  
Mechanical Fatigue ◽  
Bond Scission ◽  
Mechanical Durability

<p>Although elastomers often experience 10-100 million cycles prior to failure, there is currently a limited understanding of their resistance to fatigue crack propagation. We use soft and tough double-network elastomers tagged with mechanofluorescent probes to understand the role of damage by sacrificial bond scission on their mechanical durability and fracture toughness. Damage accumulation and localization ahead of the crack tip depend on the areal density of sacrificial bonds, as well as on the applied load (<i>i.e.</i>, cyclic or monotonic). This information serves to engineer fatigue resistant elastomers, understand fracture mechanisms, and reduce the environmental footprint of the polymer industry.</p>

scholarly journals Why is Mechanical Fatigue Different from Toughness in Elastomers? The Role of Damage by Polymer Chain Scission

2021 ◽  
Author(s):  
Gabriel Sanoja ◽  
Xavier P. Morelle ◽  
Jean Comtet ◽  
C. Joshua Yeh ◽  
Matteo Ciccotti ◽  
...  
Keyword(s):  
Applied Load ◽  
Areal Density ◽  
Chain Scission ◽  
Fracture Mechanisms ◽  
Environmental Footprint ◽  
Double Network ◽  
Mechanical Fatigue ◽  
Bond Scission ◽  
Mechanical Durability

<p>Although elastomers often experience 10-100 million cycles prior to failure, there is currently a limited understanding of their resistance to fatigue crack propagation. We use soft and tough double-network elastomers tagged with mechanofluorescent probes to understand the role of damage by sacrificial bond scission on their mechanical durability and fracture toughness. Damage accumulation and localization ahead of the crack tip depend on the areal density of sacrificial bonds, as well as on the applied load (<i>i.e.</i>, cyclic or monotonic). This information serves to engineer fatigue resistant elastomers, understand fracture mechanisms, and reduce the environmental footprint of the polymer industry.</p>

scholarly journals Crack Tip Field of a Double-Network Gel: Visualizing Covalent Bond Scission by Mechanoradical Polymerization

2020 ◽  
Author(s):  
Takahiro Matsuda ◽  
Runa Kawakami ◽  
Tasuku Nakajima ◽  
Jian Ping Gong
Keyword(s):  
Fracture Energy ◽  
Damage Zone ◽  
Crack Tip ◽  
Covalent Bond ◽  
Soft Materials ◽  
Chain Scission ◽  
Thermoresponsive Polymer ◽  
Crack Tip Field ◽  
Double Network ◽  
Bond Scission

Quantitative characterization of the energy dissipative zone around the crack tip is the central issue in fracture mechanics of soft materials. In this research, we present a mechanochemical technique to visualize the bond scission of the first network in the damage zone of tough double-network hydrogels. The mechanoradicals generated by polymer chain scission are employed to initiate polymerization of a thermoresponsive polymer, which is visualized by a fluorophore. This technique records the spatial distribution of internal fracturing from the fractured surface to the bulk, which provides the spatial profiles of stress, strain, and energy dissipation around the crack-tip. The characterized results suggest that, in addition to the dissipation in relatively narrow yielded zone which is mostly focused in the previous works, the dissipation in wide pre-yielding zone and the intrinsic fracture energy have also significant contribution to the fracture energy of a DN gel.

scholarly journals Crack Tip Field of a Double-Network Gel: Visualizing Covalent Bond Scission by Mechanoradical Polymerization

2020 ◽  
Author(s):  
Takahiro Matsuda ◽  
Runa Kawakami ◽  
Tasuku Nakajima ◽  
Jian Ping Gong
Keyword(s):  
Fracture Energy ◽  
Damage Zone ◽  
Crack Tip ◽  
Covalent Bond ◽  
Soft Materials ◽  
Chain Scission ◽  
Thermoresponsive Polymer ◽  
Crack Tip Field ◽  
Double Network ◽  
Bond Scission

Quantitative characterization of the energy dissipative zone around the crack tip is the central issue in fracture mechanics of soft materials. In this research, we present a mechanochemical technique to visualize the bond scission of the first network in the damage zone of tough double-network hydrogels. The mechanoradicals generated by polymer chain scission are employed to initiate polymerization of a thermoresponsive polymer, which is visualized by a fluorophore. This technique records the spatial distribution of internal fracturing from the fractured surface to the bulk, which provides the spatial profiles of stress, strain, and energy dissipation around the crack-tip. The characterized results suggest that, in addition to the dissipation in relatively narrow yielded zone which is mostly focused in the previous works, the dissipation in wide pre-yielding zone and the intrinsic fracture energy have also significant contribution to the fracture energy of a DN gel.

scholarly journals Why is mechanical fatigue different from toughness in elastomers? The role of damage by polymer chain scission

2021 ◽  
Vol 7 (42) ◽  
Author(s):  
Gabriel E. Sanoja ◽  
Xavier P. Morelle ◽  
Jean Comtet ◽  
C. Joshua Yeh ◽  
Matteo Ciccotti ◽  
...  
Keyword(s):  
Polymer Chain ◽  
Chain Scission ◽  
Mechanical Fatigue

scholarly journals Building Bridges: A Participatory Stakeholder Framework for Sustainable Urban Construction Logistics

2021 ◽  
Vol 13 (5) ◽  
pp. 2678
Author(s):  
Nicolas Brusselaers ◽  
Koen Mommens ◽  
Cathy Macharis
Keyword(s):  
Urban Areas ◽  
Sustainable Construction ◽  
Environmental Footprint ◽  
Implementation Barriers ◽  
Urban Construction ◽  
Multi Level ◽  
Negative Impacts ◽  
Roll Out ◽  
Construction Works

The urban built environment concentrates due to the growing urbanization trend, triggering construction and renovation works in urban areas. Although construction works often revitalize cities upon completion, the associated logistics activities engender a significant financial and environmental footprint if not handled appropriately. Cities have the largest potential to reduce negative impacts through requirements on construction logistics. However, today, there is a lack of knowledge within cities on how to set such demands and how to involve and manage the numerous and varying stakeholders in these processes. This paper presents a participatory decision-making framework for the governance of urban construction logistics on economic, environmental and societal levels, building further on the Multi-Actor Multi-Criteria Analysis (MAMCA). The framework was then implemented on a use case in the dense urban Brussels-Capital Region (Belgium), gathering a wide variety of stakeholders in the context of a sustainable Construction Logistics Scenario (CLS) evaluation. Special attention was paid on the identification of implementation barriers and the role of governments to facilitate the introduction and city-wide roll-out of novel CLS. Findings show how different processes are site-, actor- and condition-specific, thereby delivering a common built object which is often based on different motivations and concerns. The study proposes a flexible, replicable and upscalable framework both from an inter- and intracity perspective, which can serve to support (1) the management of processes and CLS, (2) the management of people and the community, and (3) the project and city, in the context of multi-level governance.

scholarly journals The Role of Hydrogen on the Behavior of Intergranular Cracks in Bicrystalline α-Fe Nanowires

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 294
Author(s):  
Jiaqing Li ◽  
Cheng Lu ◽  
Long Wang ◽  
Linqing Pei ◽  
Ajit Godbole ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Nanocrystalline Materials ◽  
Fracture Mechanisms ◽  
Bulk Materials ◽  
Cleavage Process ◽  
Deformation And Fracture ◽  
Dynamics Simulations ◽  
Crack Trapping ◽  
Cleavage Failure

Hydrogen embrittlement (HE) has been extensively studied in bulk materials. However, little is known about the role of H on the plastic deformation and fracture mechanisms of nanoscale materials such as nanowires. In this study, molecular dynamics simulations are employed to study the influence of H segregation on the behavior of intergranular cracks in bicrystalline α-Fe nanowires. The results demonstrate that segregated H atoms have weak embrittling effects on the predicted ductile cracks along the GBs, but favor the cleavage process of intergranular cracks in the theoretically brittle directions. Furthermore, it is revealed that cyclic loading can promote the H accumulation into the GB region ahead of the crack tip and overcome crack trapping, thus inducing a ductile-to-brittle transformation. This information will deepen our understanding on the experimentally-observed H-assisted brittle cleavage failure and have implications for designing new nanocrystalline materials with high resistance to HE.

Free Radicals Generated in Rubber during Fracture

1975 ◽  
Vol 48 (3) ◽  
pp. 445-461 ◽  
Author(s):  
K. L. DeVries
Keyword(s):  
Failure Criteria ◽  
Chain Scission ◽  
Systematic Investigation ◽  
Matrix Interaction ◽  
Filled Elastomers ◽  
Final Note ◽  
Ozone Stress ◽  
Type Of Failure ◽  
Insight Into

Abstract EPR has been used to measure molecular phenomena during fracture of elastomers. To date, because of various technical limitations, the studies have been largely confined to identification of the polymer chain scission site during fracture at low temperature in rubbers, to studying ozone-stress-induced cracking of rubber, to development of a micro-macro Griffith-type failure criteria for this type of failure, and lastly to systematic investigation of the role of filler-matrix interaction in fracture of filled elastomers. It is hoped that the brief outline presented here will give the reader some insight into the uses and potential of the EPR methods for the study of fracture. As a final note, while we have concentrated almost totally on EPR fracture studies in rubbers, there has been fairly extensive EPR work on fracture in oriented plastic, fibers, and films. Even though some of this knowledge may be transferable, directly or indirectly, to elastomers, it has not been reviewed here, but important aspects of these studies have been reviewed elsewhere.

Control of Failure Evolution in 3D Cellular Woven Composite Systems

2000 ◽  
Author(s):  
Jared N. Baucom ◽  
Mohammed A. Zikry ◽  
Yiping Qiu
Keyword(s):  
Areal Density ◽  
Textile Composites ◽  
Woven Composite ◽  
Ballistic Performance ◽  
Composite Systems ◽  
Matrix Cracks ◽  
Failure Evolution ◽  
Undesirable Property ◽  
Highly Porous

Abstract This investigation examines the role of porosity in the perforation resistance of 3-D woven fiber reinforced epoxy panels under impact by rigid projectiles at velocities of 100 to 200 m/s. Incident and residual velocities are measured to determine the energy absorption by the target. To compare samples of different areal density, the energy is normalized by the target areal density. The sample responses segregate by porosity, and the more highly porous samples absorb a greater amount of specific energy. The reason for this is unclear but may be due to the deflection of matrix cracks by pores or due to the greater flexibility of the fibers to absorb energy through tensile straining. Although porosity is generally an undesirable property in textile composites, the induction of porosity may result in reduced panel weight without degradation of ballistic performance, a clear advantage for weight minimization.

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