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۱Geometry and loading condition effects on stress distributions of adhesive joint in composite structures
اطلاعات انتشار: چهاردهمین کنفرانس سالانه مهندسی مکانیک، سال
تعداد صفحات: ۷
In this paper the influences of different loading conditions such as axial, shear and bending moment and effect of thickness of adherends and adhesive layer on stress distribution of adhesive joint are investigated. For these investigations, a mathematical modeling for analysis of adhesive joints in composite structures is present. In this model adherends are orthotropic laminates that obeys classical lamination theory, they can be either symmetric or asymmetric. Adhesive layers are made of homogeneous and isotropic materials. In this research, constitutive relations, kinematic and equilibrium equations are derived for each of the inside and outside of overlap zones.<\div>

۲Spew Fillet Effects on Edge Stress Concentration of Composite Adhesive Joints
اطلاعات انتشار: پانزدهمین کنفرانس سالانه مهندسی مکانیک، سال
تعداد صفحات: ۶
In this paper geometry effects of different cases of spew fillets on stress distributions and edge stress concentrations reduction in composite adhesive joints are investigated. To support the claim that the presence of a spew–fillet plays a very important structural role as a ‘stress reliever’ at the ends of the overlap zones, finite element analysis in the single lap composite adhesive joint with and without a spew–fillet have been used. Each of common adhesive joints contents two or more adherends and one or two adhesive layer(s). In this research adherends are assumed to be orthotropic laminates, and adhesive layer(s) behaves as an isotropic material. In this paper, at first peel and shear stress distribution diagrams and maximum (edge) stress concentration factors for different cases of spew fillets in the adhesive layer(s) are determined. These models are analyzed by using finite element method in Ansys software, with 2D solid 8 node elements. A mathematical modeling for determining peel and shear stress distributions for composite squared edge adhesive joints are derived. Then maximum (edge) stress concentration factors can applied for this mathematical modeling. Some cases of these results are validated with, mathematical modeling and Mortensen et al. research results.<\div>

۳Performance Investigation of Different Types of Adhesive T–Joints under Axial and Transverse Loading, in Composite Structures
نویسنده(ها): ،
اطلاعات انتشار: شانزدهمین کنفرانس سالانه مهندسی مکانیک، سال
تعداد صفحات: ۶
One of the common types of adhesive joints is: T–joint. This type of adhesive joint has more complexity than other types, and few researches has been done on this type of adhesive joint, so that in this paper try to investigate, performances of different types of adhesive T–joints with composite adherends under axial and transverse loading conditions. For this propose, a mathematical modeling for analyzing adhesive T–joints
with composite adherend is arrived. In this modeling adhesive layer is isotropic and linear elastic and modeled as continuously distributed linear
tensioncompression and shear springs. Adherends are orthotropic layers that modeled as wide beams and obeyed special case of classical lamination theory. Also all of these joints are modeled with finite element modeling and solved for these loading conditions, and the results from each type of adhesive T–joint (peel and shear adhesive layer stresses in composite adhesive T–joints with the same loading conditions) are
compared together. In the FEM modeling, T–joint samples are modeled 2 dimensionally (plane stress with thickness) and analyzed with Ansys software, by solid 8 node elements of plane 82. Finally the results from a sample of mathematical modeling are validated by finite element modeling results.<\div>

۴Determination Optimmum Relative Bonded Length and Ratio of Adherend Thickness to Adhesive Layer Thickness in Composite Adhesive Joints
اطلاعات انتشار: هفتمین همایش انجمن هوافضای ایران، سال
تعداد صفحات: ۶
Adhesive joints due to having, wide bonding area and low stress concentration factor and capability of joining and sealing simultaneously are the most suitable joints in composite structures. Performance of adhesive joints severely influenced by the geometry and types of these joints, so that in this paper, influences of bonded length, with respect to total length of composite adherends for two common types of single lap and double lap adhesive joints, and effects of relative thicknesses of these adherend to adhesive layer thickness, on stress distributions and maximum stresses in adhesive layer are investigated. For these purpose at first, a mathematical modeling for analysis of adhesive joints with composite adherends is present. In this model adherends are orthotropic laminates that obeyed special case of classical lamination theory. The stacking sequences can be either symmetrically or asymmetrically. Adhesive layer(s) is (are) homogenous and isotropic materials. They are modeled as continuously distributed tension\compression and shear springs. Then by using this mathematical modeling, the governing equations of the modeling are solved analytically for various specific bonding length (bonded length, with respect to total length of composite adherends) and specific adherend thickness (relative thickness of the adherend to adhesive layer thickness), adhesive layer(s) peel and shear stress distributions and the maximum magnitudes of these stresses, for each case are determined, and by investigating these results, the optimum specific bonding length and specific adherend thickness are recommended for the single lap and double lap composite adhesive joints. Also it is considerable that, the optimum point of the specific bonding length may not be the optimum point of the specific adherend thickness, so that, in this paper, 3D peel and shear stress diagrams with these two variable are investigated too, for cases that designer can vary bonding length and adherend (or adhesive layer thickness) together.<\div>

۵Transient Thermo–mechanical Modeling of Insulated Composite Sandwich Panels under Combined Fire and shock Loadings
نویسنده(ها): ، ، ،
اطلاعات انتشار: بیستمین کنفرانس سالانه مهندسی مکانیک، سال
تعداد صفحات: ۵
One of the most critical situations that may happen to composite structures is fire exposure. During the fire mechanical properties of composite materials would change dramatically. This reduction may lead to global or local failure of the structure. Predicting the fire integrity of the composite structures is one of the major scopes for the designers. In this paper an innovative method is introduced to predict the failure time for composite structure under fire exposure. An FEM model is developed using ANSYS Workbench. Appropriate mechanical and thermal properties are chosen precisely to follow conditions of the real state. The properties of composite structures are defined as non–linear or linear functions of temperature. Consequent explosion shock, hydrostatic loading and fire exposure are simulated on the structure. Finally, the total time that the structure could withstand the fire is reported.<\div>

۶Non–linear Analysis of Adhesive Joints in Composite Structures
نویسنده(ها):
اطلاعات انتشار: International Journal of Advanced Design and Manufacturing Technology، نهم،شماره۱(پياپي ۳۴)، Mar ۲۰۱۶، سال
تعداد صفحات: ۱۰
This paper presents a novel formulation and numerical solutions for adhesively bonded composite joints with non–linear (softening) adhesive behaviour. The presented approach has the capability of choosing arbitrary loadings and boundary conditions. In this model adherends are orthotropic laminates that obey classical lamination theory. The stacking sequences can be either symmetric or asymmetric. Adhesive layer(s) is (are) homogenous and isotropic material. They are modeled as continuously distributed non–linear (softening) tension\compression and shear springs. In this method by employing constitutive, kinematics and equilibrium equations, sets of differential equations for each inside and outside of overlap zones are derived. In the inside of overlap zone, the set of differential equations is non–linear, that is solved numerically. By solving these equations, shear and peel stresses in adhesive layer(s) as well as deflections, stress resultants and moment resultants in the adherends are determined. Most of adhesives have non–linear behavior, therefore unlike previous methods, in which the adhesive layers are modeled as linear materials, in the presented approach the non–linear behavior is assumed for the adhesive layer and can be used to analyze the most of adhesive joints. The numerical results reveal that in the inside of overlap zone, magnitudes of shear forces are considerably large due to high rate of variation in the bending moments. The developed results are successfully compared with those obtained by finite element analysis using ANSYS. The comparisons demonstrate the accuracy and effectiveness of the aforementioned methods.
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