Longitudinal Relaxation of a Thermally Stressed Fiber by Prismatic Dislocation Punching

1990 ◽  
Vol 209 ◽  
Author(s):  
David C. Dunand ◽  
Andreas Mortensen
Keyword(s):  
Fiber Length ◽  
Interfacial Shear Stress ◽  
Interfacial Shear ◽  
Longitudinal Stress ◽  
Shear Lag ◽  
Shear Lag Model ◽  
Cylindrical Fiber ◽  
The Matrix ◽  
Lag Model ◽  
Critical Fiber Length

ABSTRACTA model predicting the number of prismatic loops dislocation punched at the ends of a cylindrical fiber by thermal mismatch stresses is presented and compared to another based on a mismatching ellipsoid. The longitudinal stress in the fiber and the interfacial shear stress are derived by adapting a shear-lag model to the plastic portion of the interface. In certain cases, the central part of the fiber is strained by plastic and elastic interfacial shear until it exhibits no mismatch with the matrix. This leads to a critical fiber length above which the number of punched loops is constant.

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.

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.

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.

An Improved Shear-Lag Model for a Single Fiber Composite with a Ductile Matrix

2007 ◽  
Vol 334-335 ◽  
pp. 333-336
Author(s):  
Souta Kimura ◽  
Jun Koyanagi ◽  
Takayuki Hama ◽  
Hiroyuki Kawada
Keyword(s):  
Fiber Composite ◽  
Matrix Material ◽  
Single Fiber ◽  
Uniaxial Tensile ◽  
Fiber Direction ◽  
Stress Distributions ◽  
Shear Lag ◽  
Shear Lag Model ◽  
The Matrix ◽  
Lag Model

A shear-lag model is developed to predict the stress distributions in and around an isolated fiber in a single-fiber polymer matrix composite (PMC) subjected to uniaxial tensile loading and unloading along the fiber direction. The matrix is assumed to be an elasto-plastic material that deforms according to J2 flow theory. The stress distributions are obtained numerically and compared with a different shear-lag model that employs total strain theory as a constitutive equation of the matrix material. An effect of the difference between the models on the derived stress state is discussed.

Interfacial characteristics of hybrid nanocomposite under thermomechanical loading

2017 ◽  
Vol 26 (3-4) ◽  
pp. 95-103 ◽  
Author(s):  
Vijay Choyal ◽  
Shailesh I. Kundalwal
Keyword(s):  
Axial Stress ◽  
Interfacial Shear Stress ◽  
Transversely Isotropic ◽  
Hybrid Nanocomposite ◽  
Shear Lag ◽  
Shear Lag Model ◽  
Three Phase ◽  
Lag Model ◽  
Interfacial Characteristics ◽  
Good Agreement

AbstractIn this work, an improved shear lag model was developed to investigate the interfacial characteristics of three-phase hybrid nanocomposite which is reinforced with microscale fibers augmented with carbon nanotubes on their circumferential surfaces. The shear lag model accounts for (i) radial and axial deformations of different transversely isotropic constituents, (ii) thermomechanical loads on the representative volume element (RVE), and (iii) staggering effect of adjacent RVEs. The results from the current newly developed shear lag model are validated with the finite element simulations and found to be in good agreement. This study reveals that the reduction in the maximum value of the axial stress in the fiber and the interfacial shear stress along its length become more pronounced in the presence of applied thermomechanical loads on the staggered RVEs. The existence of shear tractions along the RVE length plays a significant role in the interfacial characteristics and cannot be ignored.

Predicting tensile behaviors of short flax fiber-reinforced polymer–matrix composites using a modified shear-lag model

2018 ◽  
Vol 52 (27) ◽  
pp. 3701-3713 ◽  
Author(s):  
Xiaoshuang Xiong ◽  
Shirley Z Shen ◽  
Lin Hua ◽  
Xiang Li ◽  
Xiaojin Wan ◽  
...  
Keyword(s):  
Natural Fiber ◽  
Volume Fraction ◽  
Shear Stiffness ◽  
Interfacial Shear ◽  
Fiber Reinforced ◽  
Shear Lag ◽  
Fiber Volume ◽  
Shear Lag Model ◽  
Lag Model ◽  
Fiber Matrix

Natural fiber-reinforced composites are increasingly being used in the industry. The fiber–matrix interfacial properties of the composites are influenced by many factors, including chemical treatment of the natural fiber, type of polymer matrix, composites fabrication method, and process and the service environment of the composites. In this paper, a modified shear-lag model based on a cohesive fiber/matrix interface is proposed and applied to the analysis of the stress–transfer characteristics and the tensile properties of unidirectional short flax fiber-reinforced composites. The model takes into account of the interfacial shear stiffness, bonding strength between fiber end face and matrix, fiber aspect ratio and fiber volume fraction. 3D finite element models of the composites using a cohesive zone method are used to verify the accuracy of the modified shear-lag model. The fiber tensile strength and the composite tensile elastic modulus are significantly influenced by the interfacial shear stiffness, fiber aspect ratio, and fiber volume fraction. The bonding strength between the fiber end face and the matrix only has an effect when the interfacial shear stiffness is low. The predicted results from the modified shear-lag model show good agreement with the finite element analysis and experimental results in the literature. The modified cohesive shear-lag model provides a simple and effective method for analyzing fiber axial stress, shear stress in the fiber/matrix interface, and tensile elastic modulus of the final composite.

Comparison of the Effects of Debonds and Voids in Adhesive Joints

1994 ◽  
Vol 116 (4) ◽  
pp. 533-538 ◽  
Author(s):  
J. N. Rossettos ◽  
P. Lin ◽  
H. Nayeb-Hashemi
Keyword(s):  
Lap Joints ◽  
Interfacial Shear ◽  
Shear Stresses ◽  
Shear Lag ◽  
Axial Loads ◽  
Adhesive Material ◽  
Shear Lag Model ◽  
Lag Model ◽  
Central Defect ◽  
Overlap Region

An analytical model is developed to compare the effects of voids and debonds on the interfacial shear stresses between the adherends and the adhesive in simple lap joints. Since the adhesive material above the debond may undergo some extension (either due to applied load or thermal expansion or both), a modified shear lag model, where the adhesive can take on extensional as well as shear deformation, is used in the analysis. The adherends take on only axial loads and act as membranes. Two coupled nondimensional differential equations are derived, and in general, five parameters govern the stress distribution in the overlap region. As expected, the major differences between the debond and the void occur for the stresses near the edge of the defect itself. Whether the defect is a debond or a void, is hardly discernible by the stresses at the overlap ends for central defect sizes up to the order of 70 percent of the overlap region. If the defect occurs precisely at or very close to either end of the overlap, however, differences of the order of 20 percent in the peak stresses can be obtained.

A Shear-Lag Model for Nanotube-Reinforced Composite Systems Under Transient Heat Transfer

2006 ◽  
Author(s):  
Amin Salehi-Khojin ◽  
Nader Jalili
Keyword(s):  
Heat Transfer ◽  
Mechanical Properties ◽  
Composite Structures ◽  
Transient Heat Transfer ◽  
Shear Lag ◽  
Equilibrium Equations ◽  
Shear Lag Model ◽  
Reinforced Composite ◽  
The Matrix ◽  
Lag Model

Understanding the stress transfer between nanotube reinforcements and matrix is an important factor in determining the overall mechanical properties of nanotube-reinforced composites. The classical shear-lag model in which the fiber and the matrix are equally long can not be applied to nanotube-based composite structures. Recently, a shear-lag model under mechanical loading for a concentric composite cylinder embedded with a capped nanotube has been introduced as the representative volume element (RVE). In this study, using similar approach the shear lag model is extended for a system under both mechanical and thermal loadings. The outer surface of RVE is prescribed to heating and cooling conditions, and transient heat transfer concept is used to find the temperature distribution in the matrix and on the surface of the nanotube. Using constitutive, geometrical and equilibrium equations for a given RVE, new shear-lag model for a nanotube-reinforced composite is then derived. It is demonstrated that the proposed model at room temperature could reduce to the same results obtained previously. These equations can be used to predict the mechanical properties of nanocomposite systems in real applications.

Use of an Advanced Shear-Lag Model to Obtain the Optimum Internal Damping in Short-Fiber Composites

1989 ◽  
Vol 42 (11S) ◽  
pp. S93-S99
Author(s):  
P. Hajela ◽  
C.-J. Shih
Keyword(s):  
Stress Distribution ◽  
Matrix Material ◽  
Short Fiber ◽  
Internal Damping ◽  
Shear Lag ◽  
Shear Lag Model ◽  
Damping Characteristics ◽  
The Matrix ◽  
Lag Model ◽  
Perfect Bonding

The present paper examines a modified shear-lag model for predicting the stress distribution in short fiber reinforced composite materials. The model assumes perfect bonding between the fiber and the matrix materials, and allows for the matrix material to partially sustain axial loads. The stress distribution obtained on the basis of this model is used to predict the internal damping characteristics of the composite material. These characteristics are a function of both the material properties and the geometrical layout of the composite, and are optimized by combining the analytical model with a nonlinear programming optimization algorithm. Representative numerical results are obtained for glass–epoxy and graphite–epoxy composites

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