Enhancing the toughness of composites via dynamic thiol–thioester exchange (TTE) at the resin–filler interface

2020 ◽  
Vol 11 (29) ◽  
pp. 4760-4767 ◽  
Author(s):  
Nancy Sowan ◽  
Yinan Lu ◽  
Kevin J. Kolb ◽  
Lewis M. Cox ◽  
Rong Long ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Mechanical Performance ◽  
Interfacial Stress ◽  
Adaptive Interface ◽  
Thioester Exchange

An adaptive interface employing thiol-thioester exchange (TTE) at the resin-filler interface is introduced to promote interfacial stress relaxation and improve the mechanical performance of thermosetting composites.

scholarly journals Preparation and properties of hybrid materials for high-rise constructions

2018 ◽  
Vol 33 ◽  
pp. 02075 ◽  
Author(s):  
Tatyana Matseevich
Keyword(s):  
Stress Relaxation ◽  
Epoxy Resin ◽  
Relaxation Process ◽  
Hybrid Materials ◽  
Mechanical Performance ◽  
Mechanical Relaxation ◽  
Physical Parameters ◽  
Quasi Equilibrium ◽  
High Rise ◽  
Long Time

The theme of the research is important because it allows to use hybrid materials as finishing in the high-rise constructions. The aim of the study was the development of producing coloured hybrid materials based on liquid glass, a polyisocyanate, epoxy resin and 2.4-toluylenediisocyanate. The detailed study of the process of stress relaxation at different temperatures in the range of 20-100°C was provided. The study found that the obtained materials are subject to the simplified technology. The materials easy to turn different colors, and dyes (e.g. Sudan blue G) are the catalysts for the curing process of the polymeric precursors. The materials have improved mechanical relaxation properties, possess different color and presentable, can be easily combined with inorganic base (concrete, metal). The limit of compressive strength varies from 32 to 17.5 MPa at a temperature of 20 to 100°C. The values σ∞ are from 20.4 to 7.7 MPa within the temperature range from 20 to 100°C. The physical parameters of materials were evaluated basing on the data of stress relaxation: the initial stress σ0, which occurs at the end of the deformation to a predetermined value; quasi-equilibrium stress σ∞, which persists for a long time relaxation process. Obtained master curves provide prediction relaxation behavior for large durations of relaxation. The study obtained new results. So, the addition of epoxy resin in the composition of the precursor improves the properties of hybrid materials. By the method of IR spectroscopy identified chemical transformations in the course of obtaining the hybrid material. Evaluated mechanical performance of these materials is long-time. Applied modern physically-based memory functions, which perfectly describe the stress relaxation process.

REPRESENTATION, CHARACTERIZATION AND SIMULATION OF TOOL-PART INTERACTION AND ITS EFFECTS ON PROCESS-INDUCED DEFORMATIONS IN COMPOSITES

2021 ◽  
Author(s):  
CALEB SCHOENHOLZ ◽  
DANIEL SLADE ◽  
ENRICO ZAPPINO ◽  
MARCO PETROLO ◽  
NAVID ZOBEIRY
Keyword(s):  
Mechanical Performance ◽  
Surface Condition ◽  
Mechanical Analysis ◽  
Interfacial Stress ◽  
Shear Stresses ◽  
Current Analysis ◽  
Degree Of Cure ◽  
Dimensional Changes ◽  
Tool Surface ◽  
Composites Processing

The interaction between a tool and part during composites processing contributes to the formation of residual stresses and dimensional changes. A resultant mismatch of part geometries during assembly can cause a potential loss of mechanical performance in aerospace structures. Costly shimming steps are needed to compensate for processinduced deformations and satisfy specifications on mechanical performance. Due to difficulties associated with accurate measurement of interfacial shear stresses, current analysis methods fail to represent the interaction between a tool and part throughout processing. A combined approach to represent, characterize, and simulate tool-part interaction and its effects on dimensional changes is proposed. First, a characterization method was established using a custom Dynamic Mechanical Analysis (DMA) shear test setup to measure tool-part interfacial stress development in a simulated autoclave curing environment. Tool-part interfacial stresses were characterized for Toray T800S/3900-2 UD prepreg as a function of temperature, degree of cure, strain rate, and tool surface condition. Then, a previously developed numerical model was modified to include the effects of tool-part interaction in predicting dimensional changes of L-shape parts. For validation, composite parts were fabricated on tools with different surface conditions and successfully compared to simulation results. This paper demonstrates that tool-part interaction significantly impacts the spring-in of angled composite parts. The proposed method is a comprehensive and practical approach to study and simulate the effects of tool-part interaction. The results of this paper can be used to understand the complex interaction between a tool and part throughout processing and potentially mitigate processinduced deformations.

Fracture analysis of a metal to CFRP hybrid with thermoplastic interlayers for interfacial stress relaxation using in situ thermography

2018 ◽  
Vol 193 ◽  
pp. 19-28 ◽  
Author(s):  
Jannik Summa ◽  
Michael Becker ◽  
Felix Grossmann ◽  
Markus Pohl ◽  
Markus Stommel ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Fracture Analysis ◽  
Interfacial Stress

Stress Relaxation Analysis of Polyurethane Foam Preloaded Structures

2010 ◽  
Vol 97-101 ◽  
pp. 871-874
Author(s):  
Bing Xu ◽  
Zhi Geng Fan ◽  
Shao Rong Yu ◽  
Wei Niu
Keyword(s):  
Stress Relaxation ◽  
Polyurethane Foam ◽  
Coulomb Friction ◽  
Mechanical Performance ◽  
Reaction Force ◽  
Viscoelastic Model ◽  
Polyurethane Foams ◽  
Structure Design ◽  
Force Relaxation ◽  
Outer Component

Based on the nonlinear finite element analysis method, FEA models which describe the viscoelastic friction contact state of the polyurethane foam preloaded structures are created. In the simulations, the general Maxwell viscoelastic constitutive relation is introduced and a seven-parameter general Maxwell viscoelastic model is used to fit the experimental stress relaxation curve of polyurethane foam. During the nonlinear contact analysis, coulomb friction law is adopted, and the effects of the coulomb friction coefficient on the reaction force in the axial direction are analyzed. The FE results show that the change tendencies of relation curves of the structures are similar to which of the polyurethane foams. In the end, the influences of stiffness ratio of polyurethane foam to the outer component on the structural relaxed force are discussed, and the FE results indicate that the stiffness ratios affect the stress (force) relaxation degree remarkably. That is to say a good structure design could optimize the mechanical performance of the complicated structures greatly.

Temperature Dependence of Stress Relaxation at the Copper/Polyimide Interface

1986 ◽  
Vol 79 ◽  
Author(s):  
S. T. Chen ◽  
C. H. Yang ◽  
H. M. Tong ◽  
P. S. Ho
Keyword(s):  
Thin Film ◽  
Stress Relaxation ◽  
Thermal Cycling ◽  
Temperature Dependence ◽  
Room Temperature ◽  
Copper Film ◽  
Interfacial Stress ◽  
Film Stress ◽  
Cross Sectional ◽  
Cu Film

AbstractA Cu/polyimide thin film couple prepared on a thin quartz reed has been used to study interfacial stress relaxation during thermal cycling between room temperature and 400 °C. The polyimide thickness varies from 0 (no polyimide at all) to 10.5μm while the Cu thickness was fixed at 0.53μm. The average copper film stress has been calculated from the curvature of the quartz reed. The information clarifies the relation between the polyimide thickness and the average Cu film stress. The Cu/polyimide interfacial morphology after thermal cycling has also been examined using the cross sectional TEM technique. The results suggest that the interfacial stress is partially released through the deformation of polyimide near the Cu/polyimide interface.

scholarly journals Surface Modification of Basalt Fibres with ZnO Nanorods and Its Effect on Thermal and Mechanical Properties of PLA-Based Composites

Biomolecules ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 200
Author(s):  
Francesca Sbardella ◽  
Andrea Martinelli ◽  
Valerio Di Lisio ◽  
Irene Bavasso ◽  
Pietro Russo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Performance ◽  
Mechanical Performance ◽  
Zno Nanorods ◽  
Stress Transfer ◽  
Interfacial Stress ◽  
Zinc Oxide Nanorods ◽  
Poly Lactic Acid ◽  
Basalt Fibre ◽  
Novel Approach

The composites based on basalt fibres and poly(lactic acid) (PLA) show promising applications in biomedical and automotive fields, but their mechanical performance is still largely hindered by poor interfacial properties. Zinc oxide nanorods have been successfully used to tune the PLA/basalt fibre interface by growing them on commercially available basalt fabrics. The hierarchical fibres significantly enhanced the mechanical properties of PLA-based composites, especially their flexural strength and stiffness. These values are 26% and 22% higher than those of unmodified basalt/PLA composites, and 24% and 34% higher than those of glass/PLA composites used as a baseline. The increase in tensile and flexural properties hinges on the mechanical interlocking action promoted by ZnO nanorods and on the creation of a compact transcrystallinity structure. A degradation of PLA matrix was detected but it was positively counteracted by the better interfacial stress transfer. This study offers a novel approach for modifying the fibre–matrix interface of biocomposites intended for high-performance applications.

Effects of nanofiller geometries and interfacial properties on the mechanical performance of polymer nanocomposites—A numerical study

2020 ◽  
pp. 096739112098363
Author(s):  
Yueqi Hu ◽  
Jow-Lian Ding ◽  
Yao Chen
Keyword(s):  
Polymer Nanocomposites ◽  
Carrying Capacity ◽  
Carbon Nanofiber ◽  
Mechanical Performance ◽  
Hybrid Composites ◽  
Numerical Study ◽  
Interfacial Stress ◽  
Material System ◽  
Load Carrying Capacity ◽  
Load Carrying

Many studies, experimental, theoretical, and numerical, have been done on polymer nanocomposites, but nearly all of them have focused on a particular type of material system or some specific material properties. A comprehensive understanding of this complicated material system is still quite lacking. The objective of this study is to use mesoscale finite element simulation to gain insights on the reinforcing efficiencies of different types of carbon nanofillers as distinguished by their geometries and interfacial strengths. It is demonstrated that CNT (carbon nanotube) and CNF (carbon nanofiber) have larger load carrying capacity and potentially higher reinforcing efficiency than GNP (graphite nanoplatelet) due to their larger aspect ratio and physical length. However, the higher load carrying capacity is also associated with higher interfacial stress which can lead to earlier debonding, particularly for CNT. GNP, on the other hand, has lower load carrying capacity, and is thus less sensitive to the bonding condition and less susceptible to debonding. The overall reinforcing efficiency is a manifestation of the interplay between the load carrying capacity of the filler, which is limited by filler’s geometry, and the load transfer capability at the interface, which is limited by the filler/matrix interfacial strength. This interplay is also reflected in the effects of filler orientation on reinforcing efficiency. The insights gained from this study can be used to devise a strategy for developing advanced nanocomposites, such as hybrid composites.

Interfacial Stress: The Importance of Stress Relaxation in TEM Cross-Sections

2004 ◽  
Vol 10 (S02) ◽  
pp. 262-263
Author(s):  
Jean Luc Rouviere ◽  
Laurent Clement ◽  
Roland Pantel ◽  
Loek F T Kwakman
Keyword(s):  
Stress Relaxation ◽  
Cross Sections ◽  
Interfacial Stress

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Stress Relaxation and the Formation of Silicides in the Process of the Crystallization of NI-NB Films on SI

1991 ◽  
Vol 49 ◽  
pp. 898-899
Author(s):  
N. Rozhanski ◽  
V. Lifshitz
Keyword(s):  
Thin Films ◽  
Stress Relaxation ◽  
Integrated Circuits ◽  
Direct Evidence ◽  
Alloy Film ◽  
Diffusion Barriers ◽  
Effective Barrier

Thin films of amorphous Ni-Nb alloys are of interest since they can be used as diffusion barriers for integrated circuits on Si. A native SiO2 layer is an effective barrier for Ni diffusion but it deformation during the crystallization of the alloy film lead to the appearence of diffusion fluxes through it and the following formation of silicides. This study concerns the direct evidence of the action of stresses in the process of the crystallization of Ni-Nb films on Si and the structure of forming NiSi2 islands.

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