A Shear-Lag Model for Nanotube Reinforced Piezoelectric Polymeric Composites Subjected to Electro-Thermo-Mechanical Loadings

2007 ◽  
Author(s):  
Amin Salehi-Khojin ◽  
Nader Jalili
Keyword(s):  
Active Control ◽  
Polyvinylidene Fluoride ◽  
Stress Transfer ◽  
Axial Displacement ◽  
Electrical Load ◽  
Shear Lag ◽  
Control Approach ◽  
Shear Lag Model ◽  
Piezoelectric Polymer ◽  
Lag Model

Understanding the stress transfer between nanotube reinforcements and surrounding matrix is an important factor in determining the overall mechanical properties of nanotube-reinforced composites. An efficient load transfer from the polymer matrix to the nanotube through interface is required to take the advantage of very high Young’s modulus and strength of carbon nanotubes in the composites. On the other hand, considerable energy dissipation can be obtained by interfacial slippage in the interface of nanotube and matrix which is beneficial in term of structural damping. In order to obtain a composite structure with tunable properties ranges from stiffer structure to better damper, we propose a semi-active control approach. In this method, applied electrical loading to piezoelectric polymeric matrix such as Polyvinylidene Fluoride (PVDF) reinforced with nanomaterials results in radial displacement of piezoelectric polymer corresponding to the direction and magnitude of electrical load. This leads to control of restriction effect of nanotube on the polymer segments, and consequently results in tunable interfacial adhesion between piezoelectric polymer and nanomaterials with faster response time. According to the concept of semi-active control, a shear lag model is obtained for a nanotube reinforced piezoelectric polymer under electro-thermo-mechanical loadings. As the adhesion in carbon nanotube (CNT) composite is universally present in the form of van der Waals interaction, and is the focus of this study, the shear stress and the axial displacement of nanotube and matrix in the interface zone can not be equal. This makes mathematical modeling of interface region more difficult. To solve this complexity, we propose to obtain the relative axial displacement between nanotube and polymer in the interface according to the Lennard-Jones potential function. Results indicate that as the electrical load increases, the relative displacement between nanotube and polymer increases which mean the possibility for slippage increases. Furthermore, results indicate that stiffer structures have more potential to show more switch stiffness capability.

scholarly journals Stress Transfer from Axially Loaded Fiber to Matrix in a Microcomposite

1994 ◽  
Vol 365 ◽  
Author(s):  
Chun-Hway Hsueh
Keyword(s):  
Analytical Solutions ◽  
Volume Fraction ◽  
Axial Stress ◽  
Stress Transfer ◽  
Radial Dependence ◽  
Shear Lag ◽  
Shear Lag Model ◽  
The Matrix ◽  
Lag Model ◽  
Loaded Fiber

ABSTRACTThe shear lag model has been used extensively to analyze the stress transfer in a singe fiberreinforced composite (i.e., a microcomposite). To achieve analytical solutions, various simplifications have been adopted in the stress analysis. Questions regarding the adequacy of those simplifications are discussed in the present study for the following two cases: bonded interfaces and frictional interfaces. Specifically, simplifications regarding (1) Poisson's effect, and (2) the radial dependences of axial stresses in the fiber and the matrix are addressed. For bonded interfaces, the former can be ignored, and the latter can generally be ignored. However, when the volume fraction of the fiber is high, the radial dependence of the axial stress in the fiber should be considered. For frictional interfaces, the latter can be ignored, but the former should be considered; however, it can be considered in an average sense to simplify the analysis. Comparisons among results obtained from analyses with various simplifications are made.

scholarly journals On the Stress Transfer of Nanoscale Interlayer with Surface Effects

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Quan Yuan ◽  
Mengjun Wu
Keyword(s):  
Surface Effect ◽  
Surface Elasticity ◽  
Stress Transfer ◽  
Interfacial Stress ◽  
Interlayer Thickness ◽  
Shear Lag ◽  
Multilayered Structures ◽  
Residual Surface Stress ◽  
Shear Lag Model ◽  
Lag Model

An improved shear-lag model is proposed to investigate the mechanism through which the surface effect influences the stress transfer of multilayered structures. The surface effect of the interlayer is characterized in terms of interfacial stress and surface elasticity by using Gurtin–Murdoch elasticity theory. Our calculation result shows that the surface effect influences the efficiency of stress transfer. The surface effect is enhanced with decreasing interlayer thickness and elastic modulus. Nonuniform and large residual surface stress distribution amplifies the influence of the surface effect on stress concentration.

Dynamic Shear-Lag Model for Stress Transfer in Piezoelectric Transducer Bonded to Plate

AIAA Journal ◽  
2019 ◽  
Vol 57 (5) ◽  
pp. 2123-2133 ◽  
Author(s):  
Santosh Kapuria ◽  
Bhabagrahi Natha Sharma ◽  
A. Arockiarajan
Keyword(s):  
Piezoelectric Transducer ◽  
Stress Transfer ◽  
Dynamic Shear ◽  
Shear Lag ◽  
Shear Lag Model ◽  
Lag Model

Shear Lag Model for Regularly Staggered Short Fuzzy Fiber Reinforced Composite

2014 ◽  
Vol 81 (9) ◽  
Author(s):  
S. I. Kundalwal ◽  
M. C. Ray ◽  
S. A. Meguid
Keyword(s):  
Polymer Matrix ◽  
Interfacial Shear Stress ◽  
Stress Transfer ◽  
Fiber Reinforced ◽  
Shear Lag ◽  
Fiber Reinforced Composite ◽  
Shear Lag Model ◽  
Transfer Characteristics ◽  
Reinforced Composite ◽  
Lag Model

In this article, we investigate the stress transfer characteristics of a novel hybrid hierarchical nanocomposite in which the regularly staggered short fuzzy fibers are interlaced in the polymer matrix. The advanced fiber augmented with carbon nanotubes (CNTs) on its circumferential surface is known as “fuzzy fiber.” A three-phase shear lag model is developed to analyze the stress transfer characteristics of the short fuzzy fiber reinforced composite (SFFRC) incorporating the staggering effect of the adjacent representative volume elements (RVEs). The effect of the variation of the axial and lateral spacing between the adjacent staggered RVEs in the polymer matrix on the load transfer characteristics of the SFFRC is investigated. The present shear lag model also accounts for the application of the radial loads on the RVE and the radial as well as the axial deformations of the different orthotropic constituent phases of the SFFRC. Our study reveals that the existence of the non-negligible shear tractions along the length of the RVE of the SFFRC plays a significant role in the stress transfer characteristics and cannot be neglected. Reductions in the maximum values of the axial stress in the carbon fiber and the interfacial shear stress along its length become more pronounced in the presence of the externally applied radial loads on the RVE. The results from the newly developed analytical shear lag model are validated with the finite element (FE) shear lag simulations and found to be in good agreement.

Theoretical Assessment of Stress Analysis in Short Fiber Composites

2004 ◽  
Vol 261-263 ◽  
pp. 1421-1426
Author(s):  
Hong Gun Kim ◽  
Sung Mo Yang ◽  
Hong Gil Noh ◽  
Dong Joo Lee
Keyword(s):  
Stress Concentration ◽  
Aspect Ratio ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Stress Transfer ◽  
Shear Lag ◽  
Modulus Ratio ◽  
Fiber Aspect Ratio ◽  
Shear Lag Model ◽  
Lag Model

An investigation of composite mechanics to investigate stress transfer mechanism accurately, a modification of the conventional shear lag model was attempted by taking fiber end effects into account in discontinuous composite materials. It was found that the major shortcoming of conventional shear lag theory is not being able to provide sufficiently accurate strengthening predictions in elastic regime when the fiber aspect ratio is very small. The reason is due to its neglect of stress transfer across the fiber ends and the stress concentrations that exist in the matrix regions near the fiber ends. To overcome this shortcoming, a more simplified shear lag model introducing the stress concentration factor which is a function of several variables, such as the modulus ratio, the fiber volume fraction, the fiber aspect ratio, is proposed. It is found that the modulus ratio is the most essential parameter among them. Thus, the stress concentration factor is expressed as a function of modulus ratio in the derivation. It is also found that the proposed model gives a good agreement with finite element results and has the capability to correctly predict the variations of the internal quanitities.

Cohesive-Shear-Lag Modeling of Interfacial Stress Transfer Between a Monolayer Graphene and a Polymer Substrate

2015 ◽  
Vol 82 (3) ◽  
Author(s):  
Guodong Guo ◽  
Yong Zhu
Keyword(s):  
Fracture Toughness ◽  
Shear Stress ◽  
Interfacial Shear Stress ◽  
Stress Transfer ◽  
Interfacial Shear ◽  
Interfacial Stress ◽  
Monolayer Graphene ◽  
Shear Lag ◽  
Shear Lag Model ◽  
Lag Model

Interfacial shear stress transfer of a monolayer graphene on top of a polymer substrate subjected to uniaxial tension was investigated by a cohesive zone model integrated with a shear-lag model. Strain distribution in the graphene flake was found to behave in three stages in general, bonded, damaged, and debonded, as a result of the interfacial stress transfer. By fitting the cohesive-shear-lag model to our experimental results, the interface properties were identified including interface stiffness (74 Tpa/m), shear strength (0.50 Mpa), and mode II fracture toughness (0.08 N/m). Parametric studies showed that larger interface stiffness and/or shear strength can lead to better stress transfer efficiency, and high fracture toughness can delay debonding from occurring. 3D finite element simulations were performed to capture the interfacial stress transfer in graphene flakes with realistic geometries. The present study can provide valuable insight and design guidelines for enhancing interfacial shear stress transfer in nanocomposites, stretchable electronics and other applications based on graphene and other 2D nanomaterials.

Intershell Coupling in Multiwalled Carbon Nanotubes

2006 ◽  
Author(s):  
Luis Zalamea ◽  
Hyonny Kim ◽  
R. Byron Pipes
Keyword(s):  
Load Transfer ◽  
Numerical Solutions ◽  
Stress Transfer ◽  
Deformation Mode ◽  
Transfer Model ◽  
Shear Lag ◽  
Multiwalled Carbon ◽  
Shear Transfer ◽  
Shear Lag Model ◽  
Lag Model

The interaction and load transfer between multiple shells of a multi-walled carbon nanotube (MWNT) is the subject of intense research by both analysts and experimentalists. Observations of both lubricated sliding and adhesion between the shells of the MWNT have been observed. While the atomic interactions due to simple separation have been successfully modeled by the Lennard-Jones interaction potential for graphene structures, modeling of the shearing deformation mode has been problematic. In the present work, the authors utilize two approaches in continuum mechanics to examine the shearing transfer between shells in a MWNT subjected to extensional and torsional loading wherein the load is transferred through the outer most shell to interior shells. The first approach follows the earlier developments of the authors wherein imperfect bonding between the shells is governed by a shearing transfer efficiency that varies between perfect bonding and frictionless sliding. The second approach utilizes a classical shear lag model to study the shearing transfer between the shells. A comparison between the shear lag and shear transfer models shows the equivalence of the two approaches for two-shell MWNT and numerical solutions are presented for the shear lag model for multiple layers beyond two. Agreement between the two models for multi-shells is demonstrated by varying an adjustable parameter that depends solely on the MWNT geometry. The simplicity of the shear transfer model as compared to the shear lag model constitutes an important advantage. The fundamental discrepancy between the two models lies in the fact that length dependence is inherent to the shear lag analysis, while according to the shear transfer model, stress transfer does not depend explicitly on length.

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