scholarly journals Validating the Classical Failure Criteria for Applicability to the Notched Woven-Roving Composite Materials

2014 ◽  
Vol 2014 ◽  
pp. 1-12
Author(s):  
Mohamed Mostafa Yousef Bassyouny Elshabasy
Keyword(s):  
Composite Materials ◽  
Failure Mechanism ◽  
Fiber Orientation ◽  
Shear Failure ◽  
Failure Criteria ◽  
Interfacial Shear ◽  
Current Investigation ◽  
Experimental Part ◽  
Failure Theories ◽  
Bending Loading

The classical failure criteria are phenomenological theories as they ignore the actual failure mechanism and do not concentrate on the microscopic events of failure. The main objective of the current investigation is to modify the classical failure theories to comprise the essential failure mechanism (interfacial shear failure) in the thin-layered woven-roving composite materials. An interfacial shear correction factor (MH6) is introduced into the nondimensional shear terms in the studied classical failure criteria. Thus the validity of applying these theories to the investigated material will be augmented. The experimental part of the current study is conducted on thin-layered circular specimens. The specimens are fabricated from two plies of fiber E-glass woven-roving fabric reinforced with polyester. The fabrics are laid to have [±45°] or [0°, 90°] fiber orientation. The specimens used are plain, where no macroscopic sources of stress concentration exist or having circular notches of five, seven, or nine mm radii. The specimens are subjected to low cycle completely reversed fatigue bending loading where the S-N and the R.D.-N curves are plotted for each group of specimens.

A failure criterion revision method for composite materials

2020 ◽  
pp. 096739112093966
Author(s):  
Ju Qiu ◽  
Ion Stiharu
Keyword(s):  
Composite Materials ◽  
Failure Mechanism ◽  
Failure Criterion ◽  
Failure Surface ◽  
Failure Criteria ◽  
Higher Order ◽  
Composite Failure ◽  
Failure Function ◽  
Material Behaviors

Failure criterion predictions often have substantial errors due to the complexity of failure mechanism or different material behaviors, especially composite failure. In this study, an example of delamination is employed to demonstrate the general failure criterion revision of composites. In the present research, the failure function can be raised to a higher order, and also be reduced to a lower one, by fitting the exponents of failure criterion. This method can be easily used to describe the observed, experimented, or computed data, particularly with no law or no rules. Further, the importance of this exponent revision is amplified when the failure surface becomes more complicated. The proposed approach is also to define and calculate the failure criteria of multiplying laminates.

Ontological Cross-Reducibility of Failure Theories for Composite Materials

2008 ◽  
Author(s):  
J. G. Michopoulos ◽  
A. P. Iliopoulos
Keyword(s):  
Composite Materials ◽  
Physical Nature ◽  
Failure Criteria ◽  
Design Decision ◽  
Visual Interpretation ◽  
Subjective Character ◽  
Ill Posed ◽  
The Common ◽  
Failure Theories ◽  
Attribute Space

Failure criteria have a significant role in the design of composite structural systems. Often the questions of “which criterion is more physical” and “which criterion is the best” create uncertainty in the design decision making process. To underline the ill-posed nature of both of these questions in the present paper we are describing the initial steps of an effort to address two ontological characteristics of failure criteria as they are applicable to composite materials applications. The first characteristic is the non-objective nature of failure criteria and an informal description is provided. The second characteristic is an ontologically based cross-reducibility between criteria. To underline more formally this characteristic we utilize an ontology-based framework to clarify “how a criterion relates with another” in terms of its main semantic attributes. The non-physical nature of a theory is exposed when it is evaluated from the semantic view of a systemic perspective. The human role on the formation of any failure criterion is shown to have a foundationally subjective character, thus rendering the corresponding criterion as non-objective. In the context of the second effort, the creation of classification ontology in terms of the semantic projections of failure criteria in their structural heritage and usage is created. The common attributes of failure criteria are utilized to identify the bases of the attribute space that they can be ontologically classified. Web ontology software is utilized to aid the ontological construction process and the visual interpretation of the ontological context. The derived cross-reducibility suggests that failure theories are special reductions of one another.

scholarly journals Introduction to Macroscopic Optimal Design in the Mechanics of Composite Materials and Structures

2021 ◽  
Vol 5 (2) ◽  
pp. 36
Author(s):  
Aleksander Muc
Keyword(s):  
Composite Materials ◽  
Composite Structures ◽  
Constitutive Relations ◽  
A Priori ◽  
Chemical Properties ◽  
Composite Plates ◽  
Failure Criteria ◽  
Lagrange Equations ◽  
Homogenization Methods ◽  
Mechanics Of Composite Materials

The main goal of building composite materials and structures is to provide appropriate a priori controlled physico-chemical properties. For this purpose, a strengthening is introduced that can bear loads higher than those borne by isotropic materials, improve creep resistance, etc. Composite materials can be designed in a different fashion to meet specific properties requirements.Nevertheless, it is necessary to be careful about the orientation, placement and sizes of different types of reinforcement. These issues should be solved by optimization, which, however, requires the construction of appropriate models. In the present paper we intend to discuss formulations of kinematic and constitutive relations and the possible application of homogenization methods. Then, 2D relations for multilayered composite plates and cylindrical shells are derived with the use of the Euler–Lagrange equations, through the application of the symbolic package Mathematica. The introduced form of the First-Ply-Failure criteria demonstrates the non-uniqueness in solutions and complications in searching for the global macroscopic optimal solutions. The information presented to readers is enriched by adding selected review papers, surveys and monographs in the area of composite structures.

scholarly journals Buckling Failure Mechanism of a Rock Dam Foundation Fractured by Gentle Through-Going and Steep Structural Discontinuities

2020 ◽  
Vol 12 (13) ◽  
pp. 5426
Author(s):  
Donghui Chen ◽  
Huie Chen ◽  
Wen Zhang ◽  
Chun Tan ◽  
Zhifa Ma ◽  
...  
Keyword(s):  
Numerical Method ◽  
Failure Mechanism ◽  
Shear Failure ◽  
Distinct Element ◽  
Mechanism Analysis ◽  
Rock Masses ◽  
Dam Foundation ◽  
Deformation Features ◽  
Universal Distinct Element Code ◽  
Distinct Element Code

The failure mechanism analysis of dam foundations is key for designing hydropower stations. This study analyses the rock masses in a sluice section, which is an important part of the main dam of the Datengxia Hydropower Station currently built in China. The stability of the sluice rock masses is predominantly affected by gentle through-going soft interlayers and steep structural fractures. Its foundation failure mechanism is investigated by means of a numerical method, i.e., Universal Distinct Element Code (UDEC) and the geomechanical model method. The modeling principle and process, and results for the rock dam foundation are introduced and generated by using the abovementioned two methods. The results indicate that the failure mechanism of the foundation rock masses, as characterized by gentle through-going and steep structural discontinuities, is not a conventional type of shear failure mechanism but a buckling one. This type of failure mechanism is verified by analyzing the deformation features resulting from the overloading of both methods and strength reduction of the numerical method.

scholarly journals Analytical investigation of high-velocity impact on hybrid unidirectional/woven composite panels

2016 ◽  
Vol 30 (4) ◽  
pp. 545-563 ◽  
Author(s):  
H Shanazari ◽  
GH Liaghat ◽  
H Hadavinia ◽  
A Aboutorabi
Keyword(s):  
Cross Sections ◽  
Shear Failure ◽  
Failure Criteria ◽  
Analytical Investigation ◽  
Woven Fabrics ◽  
Body Armor ◽  
Ballistic Performance ◽  
Nonwoven Fabrics ◽  
Ballistic Protection ◽  
Maximum Tensile Strain

In addition to fiber properties, the fabric structure plays an important role in determining ballistic performance of composite body armor textile. Textile structures used in ballistic protection are woven fabrics, unidirectional (UD) fabric structures, and nonwoven fabrics. In this article, an analytical model based on wave propagation and energy balance between the projectile and the target is developed to analyze hybrid fabric panels for ballistic protection. The hybrid panel consists of two types of structure: woven fabrics as the front layers and UD material as the rear layers. The model considers different cross sections of surface of the target in the woven and UD fabric of the hybrid panel. Also the model takes into account possible shear failure by using shear strength together with maximum tensile strain as the failure criteria. Reflections of deformation waves at interface between the layers and also the crimp of the yarn are modeled in the woven part of the hybrid panel. The results show greater efficiency of woven fibers in front layers (more shear resistance) and UD yarns in the rear layers (more tensile resistance), leading to better ballistic performance. Also modeling the yarn crimp results in more trauma at the backface of the panel producing data closer to the experimental results. It was found that there is an optimum ratio of woven to UD materials in the hybrid ballistic panel.

scholarly journals Strength and Failure Mechanism of Composite-Steel Adhesive Bond Single Lap Joints

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Kai Wei ◽  
Yiwei Chen ◽  
Maojun Li ◽  
Xujing Yang
Keyword(s):  
Failure Mechanism ◽  
Shear Failure ◽  
Failure Load ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Adhesive Failure ◽  
Interface Failure ◽  
Element Analysis ◽  
Single Lap Joints ◽  
Structural Adhesive

Carbon fiber-reinforced plastics- (CFRP-) steel single lap joints with regard to tensile loading with two levels of adhesives and four levels of overlap lengths were experimentally analyzed and numerically simulated. Both joint strength and failure mechanism were found to be highly dependent on adhesive type and overlap length. Joints with 7779 structural adhesive were more ductile and produced about 2-3 kN higher failure load than MA830 structural adhesive. Failure load with the two adhesives increased about 147 N and 176 N, respectively, with increasing 1 mm of the overlap length. Cohesion failure was observed in both types of adhesive joints. As the overlap length increased, interface failure appeared solely on the edge of the overlap in 7779 adhesive joints. Finite element analysis (FEA) results revealed that peel and shear stress distributions were nonuniform, which were less severe as overlap length increased. Severe stress concentration was observed on the overlap edge, and shear failure of the adhesive was the main reason for the adhesive failure.

scholarly journals Physical modelling of failure in composites

2016 ◽  
Vol 374 (2071) ◽  
pp. 20150280 ◽  
Author(s):  
Ramesh Talreja
Keyword(s):  
Composite Materials ◽  
Failure Modes ◽  
Structural Integrity ◽  
Failure Mechanisms ◽  
Local Stress ◽  
Physical Modelling ◽  
Stress Fields ◽  
Systematic Analysis ◽  
Composite Failure ◽  
Failure Theories

Structural integrity of composite materials is governed by failure mechanisms that initiate at the scale of the microstructure. The local stress fields evolve with the progression of the failure mechanisms. Within the full span from initiation to criticality of the failure mechanisms, the governing length scales in a fibre-reinforced composite change from the fibre size to the characteristic fibre-architecture sizes, and eventually to a structural size, depending on the composite configuration and structural geometry as well as the imposed loading environment. Thus, a physical modelling of failure in composites must necessarily be of multi-scale nature, although not always with the same hierarchy for each failure mode. With this background, the paper examines the currently available main composite failure theories to assess their ability to capture the essential features of failure. A case is made for an alternative in the form of physical modelling and its skeleton is constructed based on physical observations and systematic analysis of the basic failure modes and associated stress fields and energy balances. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’.

A numerical approach to predict soil bearing potential for isolated footing

2021 ◽  
Author(s):  
Gilbert Hinge ◽  
Jayanta Kumar Das ◽  
Biswadeep Bharali
Keyword(s):  
Bearing Capacity ◽  
Shear Failure ◽  
Correlation Coefficients ◽  
Failure Criteria ◽  
Numerical Approach ◽  
Ultimate Bearing Capacity ◽  
Foundation Design ◽  
Advantages And Disadvantages ◽  
Local Shear ◽  
Failure Conditions

<p>The success of any civil engineering structure's foundation design depends upon the accuracy of estimation of soil’s ultimate bearing capacity. Numerous numerical approaches have been proposed to estimate the foundation's bearing capacity value to avoid repetitive and expensive experimental work. All these models have their advantages and disadvantages. In this study, we compiled all the governing equations mentioned in Bureau of Indian standard IS:6403-1981 and modify the equation for Ultimate Bearing Capacity. The equation was modified by considering two new parameters, K1(for general shear) and K2 (for local shear) so that a common governing equation can be used for both general and local shear failure criteria. The program used for running the model was written in MATLAB language code and verified with the observed field data. Results indicate that the proposed model accurately characterized the ultimate, safe, and allowable bearing capacity of a shallow footing at different depths. The correlation coefficients between the observed and model-predicted bearing capacity values for a 2m foundation depth with footing size of 1.5 ×1.5, 2.0 × 2.0, and 2.5 × 2.5 m are 0.95, 0.94, and 0.96. A similar result was noted for the other foundation depth and footing size. Findings show that the model can be used as a reliable tool for predicting the bearing capacity of shallow foundations at any given depth.  Moreover, the formulated model can also be used for the transition zone between general and local shear failure conditions.</p>

THE EFFECT OF LAMINATION SCHEME AND ANGLE VARIATIONS TO THE DISPLACEMENTS AND FAILURE BEHAVIOUR OF COMPOSITE LAMINATE

2015 ◽  
Vol 76 (11) ◽  
Author(s):  
Azizul Hakim Samsudin ◽  
Jamaluddin Mahmud
Keyword(s):  
Fiber Orientation ◽  
Composite Laminates ◽  
Finite Element Modelling ◽  
Composite Laminate ◽  
Maximum Stress ◽  
Failure Load ◽  
Failure Criteria ◽  
Stress Theory ◽  
Failure Behaviour ◽  
Failure Index

This paper aims to investigate the effect of lamination scheme and angle variations to the displacements and failure behaviour of composite laminate. Finite element modelling and analysis of symmetric, anti-symmetric and angle-ply Graphite/ Epoxy laminate with various angles of fiber orientation subjected to uniaxial tension are performed. Maximum Stress Theory and Tsai-Wu Failure Criteria are employed to determine the failure load (failure index = 1). Prior to that, convergence analysis and numerical validation are carried out. Displacements and failure behaviour of the composite laminates (symmetric, anti-symmetric and angle ply) are analysed. The failure curves (FPF and LPF) for both theories (Maximum Stress Theory and Tsai-Wu) are plotted and found to be very close to each other. Therefore, it can be concluded that the current study is useful and significant to the displacements and failure behaviour of composite laminate.

scholarly journals An Experimental Study on Shear Failure Mechanism of RC Interior Beam-Column Joints

1997 ◽  
Vol 8 (2) ◽  
pp. 39-49
Author(s):  
Yasuaki Goto ◽  
Osamu Joh ◽  
Takuji Shibata
Keyword(s):  
Experimental Study ◽  
Failure Mechanism ◽  
Shear Failure
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