Numerical Evaluation of Ultimate Strengths of Composites Considering Both In-Plane Damage and Delamination

2006 ◽  
Vol 324-325 ◽  
pp. 771-774 ◽  
Author(s):  
Wen Jie Peng ◽  
Jian Qiao Chen
Keyword(s):  
Failure Mode ◽  
Failure Modes ◽  
Mechanical Load ◽  
Three Dimensional ◽  
Boundary Region ◽  
Stress Fields ◽  
Strength Analysis ◽  
Singular Stress ◽  
Singular Stress Fields ◽  
Good Agreement

Traditional laminate strength analysis only considers face failure under in-plane loads. In fact, owing to the mismatch of the mechanical properties of the adjacent layers, a three-dimensional interlaminar singular stress fields develop in a small boundary region in the vicinity of the free edges of the laminate under mechanical load, which may lead to interlaminar delamination failure. Neglecting this interlaminar failure mode, the failure strength of laminate will be overestimated. In this paper, face failure and interlaminar failure are both considered. So for a lamina, three major failure modes are considered: matrix failure, fiber breakage and delamination. Finite element method is used to obtain the stresses in a laminate under mechanical loads. Stress-based criterions are adopted to predict the failure mode of laminas. When a lamina is failed, the lamina stiffness is reduced according to the corresponding failure mode, and the stresses of the laminate are re-analyzed. This procedure is repeatedly performed until the whole laminate fails and thus the ultimate strength is determined. The predicted ultimate strengths are in good agreement with experiment results in the open literature.

Application of Stress Intensity to Design of Bi-Materials with a Wedge

2011 ◽  
Vol 413 ◽  
pp. 223-228
Author(s):  
Xue Cheng Ping ◽  
Xing Li ◽  
Xiao Xiang Xu
Keyword(s):  
Failure Criterion ◽  
Mechanical Load ◽  
Stress Component ◽  
Lap Joints ◽  
Stress Fields ◽  
Aviation Industry ◽  
Displacement Fields ◽  
Singular Stress ◽  
Glass Fiber Reinforced ◽  
Singular Stress Fields

Failure in anisotropic/isotropic bi-materials starts at the interface, and the interfacial failure is of interest to some engineering fields such as automobile and aviation industry. Many researchers have done a lot of research on this field, but many did not consider a specific stress component near the interface corner tip as a parameter of a failure criterion. Kun Cheol Shin, introducted a failure criterion for anisotropic/isotropic bi-materials problem with a wedge. But the process of obtaining the singular stress fields of anisotropic/isotropic bi-materials is complex. To solve this problem, we have taken a new method which is from Xuecheng-Ping and M.-C. Chen.The method is new, which is based on displacement and more easily in calculating the stress and displacement fields surrounding a wedge tip than before. Through this method, we establish a criterion base on the-plan. The failure criterion can be used not only to predict stress intensities of co-cured double lap joints that with thermal and mechanical load, but also to predict stress intensities of co-cured double lap joints that with different materials or lap length. And we describe the process of calculating singular stress fields and stress intensities of co-cured double lap joints with a wedge that consists of glass fiber reinforced composites and steel adherends.

A Super Singular Element for Three-Dimensional Corner Fronts

2016 ◽  
Author(s):  
Xuecheng Ping ◽  
Mengcheng Chen ◽  
Wei Zhu
Keyword(s):  
Three Dimensional ◽  
Stress Singularity ◽  
High Accuracy ◽  
Stress Fields ◽  
Singular Element ◽  
Field Boundary ◽  
Singular Stress ◽  
Numerical Studies ◽  
Singular Stress Fields ◽  
Eigen Solutions

Three-dimensional (3-D) solids containing corner configurations with straight corner fronts are considered. A super polygonal prismatic element containing a straight corner front is established by using the numerical eigen-solutions of singular stress fields and Hellinger-Reissner variational principle. Singular stresses near corner fronts for far-field boundary conditions can be obtained by incorporating the super singular element with the conventional three-dimensional (3-D) brick elements. The numerical studies are conducted to demonstrate the simplicity of the proposed technique in handling fracture problems of 3-D through-thickness cracks. The usage of the super singular element can avoid mesh refinement near the corner front domain, and the simulation results have high accuracy and fast convergence speed. Compared with the conventional finite element methods and existing analytical methods, the present method is more suitable for dealing with complicated problems of stress singularity in elasticity including multiple defects.

Computations of Singular Stresses Along Three-Dimensional Corner Fronts by a Super Singular Element Method

2017 ◽  
Vol 14 (06) ◽  
pp. 1750065 ◽  
Author(s):  
Xuecheng Ping ◽  
Mengcheng Chen ◽  
Wei Zhu ◽  
Yihua Xiao ◽  
Weixing Wu
Keyword(s):  
Finite Element ◽  
Finite Element Methods ◽  
Three Dimensional ◽  
Stress Singularity ◽  
Stress Fields ◽  
Singular Element ◽  
Singular Stress ◽  
Numerical Studies ◽  
Enriched Finite Element ◽  
Singular Stress Fields

In order to consider corner configurations with straight corner fronts in three-dimensional (3D) solids, a super polygonal prismatic element containing a straight corner front is established by using the numerical eigensolutions of singular stress fields and the Hellinger–Reissner variational principle. Singular stresses near the corner front subject to far-field boundary conditions can be obtained by incorporating the super singular element with conventional 3D brick elements. The numerical studies are conducted to demonstrate the simplicity of the proposed technique in handling fracture problems of 3D corner configurations and cracks. The usage of the super singular element can avoid mesh refinement near the corner front domain that is necessary for conventional and enriched finite element methods, and lead to high accuracy and fast convergence. Compared with the conventional finite element methods and existing analytical methods, the present method is more suitable for dealing with complicated problems of stress singularity in elasticity including multiple defects.

Analysis of Singular Stress Fields at 3D Piezoelectric Bonded Joints Using a Conservative Integral

2016 ◽  
Author(s):  
Chonlada Luangarpa ◽  
Hideo Koguchi
Keyword(s):  
Three Dimensional ◽  
Stress Singularity ◽  
Stress Fields ◽  
Bonded Joints ◽  
Singular Stress ◽  
Conservative Integral ◽  
Dimensional Finite Element ◽  
Refined Meshes ◽  
Singular Stress Fields ◽  
Three Dimensional Finite Element

Singular stress fields at a vertex of the interface in three-dimensional piezoelectric bonded joints are analyzed. A conservative integral based on the Betti reciprocal principle is applied for calculating the intensities of singularities. Eigenanalysis formulated using a three-dimensional finite element method (FEM) is used to calculate the order of stress singularity, angular functions of mechanical displacements, stresses, electric displacements and electric potential. A bimaterial bonded joint with three terms of singularities is investigated. In order to study the influence of mesh refinement and integral area on the accuracy of the results, two models with different element sizes and various integral areas are used. The results are compared with those obtained from conventional FEM, in which using extremely refined meshes near the singular point.

The detachment of an inclined micro-pillar adhered to a dissimilar substrate

2021 ◽  
pp. 1-22
Author(s):  
Nitish Kumar ◽  
Syed Nizamuddin Khaderi
Keyword(s):  
Stress Intensity ◽  
Axial Load ◽  
Interfacial Crack ◽  
Axial Loading ◽  
Stress Fields ◽  
Singular Stress ◽  
Elastic Mismatch ◽  
Bending Loads ◽  
Singular Stress Fields ◽  
The Moment

Abstract We investigate the mechanics of the detachment of an inclined micro-pillar adhered to a dissimilar substrate when subjected to a combination of an axial load and end moment. When the micro-pillar has adhered to the substrate, singular stress fields exist at the bi-material corners. The order of singularity is estimated using asymptotic analysis. The first two terms in the asymptotic expansion lead to singular stress fields. The magnitude of the singularity is evaluated in terms of the elastic mismatch between the pillar and substrate and the micro-pillar inclination. The asymptotic stress due to the moment loading is more sensitive to the micro-pillar inclination when compared to that due to the axial loading. They are insensitive to the micro-pillar inclination when the micro-pillar is rigid when compared to the substrate. A short interfacial crack is further assumed to exist at the bi-material corner. This crack is embedded in the corner singularity region and is loaded by the singular fields due to axial and bending loads. A boundary layer analysis is performed on the singular zone to estimate the stress intensity factor when a short crack embedded in it is subjected to the singular fields. The stress intensity factors are also calculated for a long interfacial crack at the bi-material corner, which extends beyond the singular zone. Using the above results, we investigate the detachment of the inclined micro-pillar under the combination of an axial load and end moment.

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