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.

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.

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.

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.

Time-Dependent Lateral Transmission of Force in Skeletal Muscle

2009 ◽  
Author(s):  
Yingxin Gao ◽  
Alan S. Wineman ◽  
Anthony M. Waas
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fibers ◽  
Essential Element ◽  
Stress Transfer ◽  
Time Dependent ◽  
Shear Stresses ◽  
Shear Lag ◽  
Shear Lag Model ◽  
Lag Model ◽  
Whole Muscle

The composite structure of skeletal muscle is composed of muscle fibers and an extracellular matrix (ECM) framework. This framework is associated with different levels of structure: (a) epimysium, that ensheaths the whole muscle; (b) perimysium, that binds a group of muscle fibers into bundles and (c) endomysium that surrounds the individual muscle fibers. The properties of ECM components and their interaction with muscle fibers determine the overall mechanical properties of the whole muscle. Previous studies have experimentally demonstrated that stress could be laterally transmitted through the ECM [1]. The ECM is thus an essential element in mechanical function of the muscle [2]. The most widely used model describing load transfer between a discontinuous fiber and matrix is the shear lag model, originally proposed by Cox [3]]. This model centers on the transfer of tensile stress between fibers by means of interfacial shear stresses and shear deformation of the matrix. In this paper, a modified shear lag model is developed to investigate the time-dependent mechanics of stress transfer between activated muscle fibers and the surrounding strained ECM.

Evidence for Interfibrillar Shear Load Transfer Between Sliding Fibrils in Tendon

2013 ◽  
Author(s):  
Spencer E. Szczesny ◽  
Dawn M. Elliott
Keyword(s):  
Load Transfer ◽  
Tensile Load ◽  
Tissue Level ◽  
Collagen Fibrils ◽  
Shear Stresses ◽  
Shear Lag ◽  
Shear Lag Model ◽  
Lag Model ◽  
Tail Tendon ◽  
The Impact

While collagen fibrils are understood to be the primary tensile load bearing components in tendon, how loads applied at the tissue level are transmitted across each element within the tissue hierarchical structure is unclear. A central unresolved question is whether collagen fibrils bear load independently or if the applied load is transferred across the fibrils through interfibrillar shear forces. Relative sliding between fibrils is suggested by findings that fibril strains within rat tail tendon fascicles do not agree with the applied tissue tensile strains [1]. Other studies using confocal microscopy have directly measured sliding behavior [2,3]; however, the impact that interfibrillar sliding has on tendon macroscale mechanics and whether sliding is associated with interfibrillar shear stresses are unknown. Therefore, the objective of this work is to quantify the contribution of interfibrillar sliding on tendon macroscale mechanics by simultaneously measuring the tissue behavior at both length-scales and interpreting the results with a micro-structural shear lag model directly incorporating interfibrillar shear stresses. We hypothesize that the reduced stiffness and increased viscosity observed in the tissue macroscale properties at higher strains are due to increases in interfibrillar sliding and that this behavior is consistent with a shear lag model involving interfibrillar shear stress.

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.

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