scholarly journals Micromechanical Analyses of Debonding and Matrix Cracking in Dual-Phase Materials

2016 ◽  
Vol 83 (5) ◽  
Author(s):  
Brian Nyvang Legarth ◽  
Qingda Yang
Keyword(s):  
Biaxial Loading ◽  
Matrix Cracking ◽  
Dual Phase ◽  
Load Carrying Capacity ◽  
Matrix Cracks ◽  
Loading Direction ◽  
Load Carrying ◽  
The Matrix ◽  
Cohesive Zones ◽  
Good Agreement

Failure in elastic dual-phase materials under transverse tension is studied numerically. Cohesive zones represent failure along the interface and the augmented finite element method (A-FEM) is used for matrix cracking. Matrix cracks are formed at an angle of 55 deg−60 deg relative to the loading direction, which is in good agreement with experiments. Matrix cracks initiate at the tip of the debond, and for equi-biaxial loading cracks are formed at both tips. For elliptical reinforcement the matrix cracks initiate at the narrow end of the ellipse. The load carrying capacity is highest for ligaments in the loading direction greater than that of the transverse direction.

scholarly journals Design of steering system of a buggy

2020 ◽  
Vol 327 ◽  
pp. 03004
Author(s):  
D. Santana Sanchez ◽  
A. Mostafa
Keyword(s):  
Carrying Capacity ◽  
Steering System ◽  
Nonlinear Finite Element ◽  
Load Carrying Capacity ◽  
Dynamic Effects ◽  
Flexural Behaviour ◽  
Steering Angle ◽  
Load Carrying ◽  
And Performance ◽  
Good Agreement

The present paper discusses the design analysis and limitations of the steering system of a buggy. Many geometrical and performance characteristics of the designed steering system were considered to address the kinematic constraints and load carrying capacity of the steering elements. Ackremann geometry approach was used to assess the limiting steering angle, while Lewis bending formula with the inclusion of dynamic effects was employed to characterise the flexural properties of the rack and pinion steering system. Analytical results were numerically verified using ABAQUS/Explicit nonlinear finite element (FE) package. Good agreement has been achieved between analytical and numerical results in predicting the flexural behaviour of the steering rack and pinion system.

Measurement of Residual Strains As a Parameter of Matrix Cracking in CFRP Laminates

2020 ◽  
Author(s):  
M. J. Mohammad Fikry ◽  
Shinji Ogihara ◽  
Vladimir Vinogradov
Keyword(s):  
Viscoelastic Behavior ◽  
Matrix Cracking ◽  
Time Dependent ◽  
Strain Gauges ◽  
Recovery Test ◽  
Cfrp Laminates ◽  
Matrix Cracks ◽  
Theoretical Predictions ◽  
Residual Strains ◽  
Good Agreement

Abstract Matrix cracking in CFRP laminates results in degradation of mechanical properties of the material and appearance of residual strains. In this study, the residual strains investigated are experimentally and analytically for CFRP [0/756]s laminates. The strain gauges were used in this study to measure the strains. Due to very small residual strains at the unloading condition, the residual strains were also measured at different stress levels for laminates with different crack densities and are compared with theoretical predictions. Time-dependent viscoelastic behavior of the material is also considered to accurately measure the residual strains due to the occurrence of matrix cracks. This was done by using the strain recovery test when the loads were stopped for 1–1.5 hours during unloading and the strain changes during these times were recorded. The experimental results of the residual strains are in reasonably good agreement with the theoretical predictions. The fiber non-linearity properties of the laminates may cause some experimental data to shift above the analytical line.

Theoretical Investigation of Couple Stress Squeeze Films in a Curved Circular Geometry

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Vimala Manivasakan ◽  
Govindarajan Sumathi
Keyword(s):  
Theoretical Investigation ◽  
Carrying Capacity ◽  
Couple Stress ◽  
Squeeze Flow ◽  
Squeeze Film ◽  
Load Carrying Capacity ◽  
Fluid Inertia ◽  
Load Carrying ◽  
Inertia Forces ◽  
Good Agreement

A theoretical investigation of the laminar squeeze flow of a couple-stress fluid between a flat circular static disk and an axisymmetric curved circular moving disk has been carried out using modified lubrication theory and microcontinuum theory. The combined effects of fluid inertia forces, curvature of the disk and non-Newtonian couple stresses on the squeeze film behavior are investigated analytically. Each of these effects and their combinations show a significant enhancement in the squeeze film behavior, and these are studied through their effects on the squeeze film pressure and the load carrying capacity of the fluid film as a function of time. Two different forms of the gapwidth between the disks have been considered, and the results have been shown to be in good agreement with the existing literature.

Matrix cracking and the mechanical behaviour of SiC─CAS composites

1992 ◽  
Vol 437 (1899) ◽  
pp. 109-131 ◽  
Keyword(s):  
Elastic Properties ◽  
Three Dimensional ◽  
Matrix Cracking ◽  
Repeated Loading ◽  
Matrix Composites ◽  
Pull Out ◽  
Matrix Cracks ◽  
Brittle Matrix Composites ◽  
Dimensional Network ◽  
The Matrix

An experimental investigation has been carried out on the mechanical properties of unidirectional (0) 12 , (0, 90) 3S , (±45, 0 2 ) S , and (±45) 3S composites consisting of CAS glass ceramic reinforced with Nicalon SiC fibres. Measurements have been made of the elastic properties and of the tensile, compression and shear strengths of the composites, and these have been supported by a detailed study of the damage which occurs during monotonic and repeated loading. These damage studies have been carried out by means of edge replication microscopy and acoustic emission monitoring. The elastic properties of the composites are, by and large, close to the values that would be predicted from the constituent properties and lay-up sequences, but their strengths are lower than expected, and it appears that the Nicalon reinforcing fibre has been seriously degraded during manufacture. The fracture energy is much higher than predicted from observations of fibre pull-out, and it is suggested that the energy required to form a close three-dimensional network of matrix cracks could account for the high apparent toughness. The matrix cracking stress can be predicted reasonably closely by the Aveston, Cooper and Kelly model of cracking in brittle matrix composites, but it is shown that subcritical microcracks can form and/or grow at stresses well below the predicted critical values without affecting composite properties.

scholarly journals Development of Delamination in Cross-Ply Laminates: Effect of Microstructure

2009 ◽  
Vol 413-414 ◽  
pp. 229-236 ◽  
Author(s):  
Zahid R. Khokhar ◽  
Ian A. Ashcroft ◽  
Vadim V. Silberschmidt
Keyword(s):  
Random Fields ◽  
Cohesive Zone ◽  
Effective Properties ◽  
Axial Stress ◽  
Damage Mechanism ◽  
Stress Concentrations ◽  
Matrix Cracks ◽  
Load Carrying ◽  
The Matrix ◽  
Cohesive Zone Elements

Various aspects of the effect of microstructural randomness exhibited by carbon fibre-reinforced cross-ply laminates on the delamination damage mechanism is investigated in this paper. In the first part, the matrix cracks with different spacings measured in experiments are simulated using finite elements in order to obtain the levels of degradation and effective properties for a composite beam loaded in bending. The results show significant levels of degradation of obtained effective properties depicting the importance of accounting for the inherent stochasticity in these laminates. In the second part of the paper, initiation of delamination at an interface between 0° and 90° layers due to stress concentrations at tips matrix cracks is simulated for a beam under tension. Stochastic cohesive zone elements with fracture parameters presented as random fields are used to model this interface in a composite. Different values of the axial stress are obtained for initiation of damage for a number of realisations based on this approach. The results emphasize the need to take into consideration the microstructural randomness in fibre-reinforced laminates for adequate predictions of damage and load carrying capacities.

Load-Carrying Behaviour of Dowel-Type Timber Connections with Multiple Slotted-in Steel Plates

2011 ◽  
Vol 94-96 ◽  
pp. 43-47
Author(s):  
Xin Hai Fan ◽  
Sheng Dong Zhang ◽  
Wen Jun Qu
Keyword(s):  
Carrying Capacity ◽  
Steel Plates ◽  
Load Carrying Capacity ◽  
Timber Structures ◽  
Lateral Loads ◽  
Large Cross Section ◽  
Load Carrying ◽  
Timber Connections ◽  
Dowel Connection ◽  
Good Agreement

The multiple-shear dowel connection with slotted-in steel plates is one of the most efficient joints for large cross section timber structures. Experiments were performed on dowel-type timber connections with one, two and three slotted in steel plates under lateral loads parallel to the grain. Test variables include the number of steel plates, the spacing of the steel plates, and the dowel diameter. Results show that the load-carrying capacity of the dowel-type connection increased as the number and spacing of steel plates in the same thickness of timber specimens. Finally, a model of the load-carrying capacity of multiple shear steel-to-timber connections is presented, which showed good agreement with the results obtained in the experiment.

Numerical study of GFRP joints bearing strength reduction due to drilling-induced delamination

2019 ◽  
Vol 54 (16) ◽  
pp. 2185-2194 ◽  
Author(s):  
M Safarabadi ◽  
M Sardar
Keyword(s):  
Parametric Study ◽  
Cohesive Zone ◽  
Volume Fraction ◽  
Numerical Study ◽  
Load Carrying Capacity ◽  
Zone Method ◽  
Bearing Strength ◽  
Load Carrying ◽  
Negative Effect ◽  
Good Agreement

Delamination is one of the most common defects caused by drilling, which can have negative effect on the joint performance. This study investigates the effect of delamination on the bearing strength of [0/90]2s, [15/−75]2s, [30/−60]2s and [45/−45]2s GFRP layers numerically. Cohesive zone method and virtual crack closure technique have been used for delamination modeling and the results of these two methods have been compared. FEM results show good agreement with available experimental data. Results demonstrated that delamination reduces the bearing strength. Among four different stacking sequences, delamination has the most effect on the laminate with the stacking sequence of [0/90]2s. In both delaminated and non-delaminated models, [0/90]2s and [45/−45]2s stacking sequences have the most and the least bearing strength, respectively. By increasing the radius of delaminated zone from 3 mm to 15 mm, bearing strength does not change a lot. As the delaminated zone reaches the edge of the specimen, bearing strength reduces strongly because the layers separate completely and the load-carrying capacity reduces. A parametric study was also conducted to examine the effects of different factors. The results of parametric study showed that by increasing the volume fraction of the fiber as well as the use of carbon fiber instead of glass fiber, the bearing strength increases.

Pitting Resistance and Bending Strength of Bevel and Hypoid Gear Teeth

1992 ◽  
Author(s):  
B.-R. Höhn ◽  
H. Winter ◽  
K. Michaelis ◽  
F. Vollhüter
Keyword(s):  
Bending Strength ◽  
Load Carrying Capacity ◽  
Test Results ◽  
Hypoid Gear ◽  
Hypoid Gears ◽  
Gear Teeth ◽  
Bevel Gears ◽  
Load Carrying ◽  
Calculation Results ◽  
Good Agreement

Abstract Bevel and hypoid gears are widely used for gears with crossed axis. The influence of a pinion offset on the load carrying capacity — pitting resistance and bending strength — is introduced in a different way in commonly used calculation methods. Load carrying and measurement investigations on the influence of pinion offset on pitting resistance and bending strength are reported. Tests show an increasing bending strength and decreasing maximum tooth root stresses with increasing pinion offset. Also a slight increase of pitting resistance and a slight decrease of the Hertzian pressure was evaluated. The load carrying calculation results for bevel gears without pinion offset, DIN 3991, is in good agreement with test results. The bending strength of hypoid gears calculated according to Niemann/Winter, is greater than that experimentally measured. For pitting resistance, however, the calculation is less than the measured results.

Effect of matrix cracking on the overall thermal conductivity of fibre-reinforced composites

1995 ◽  
Vol 351 (1697) ◽  
pp. 595-610 ◽  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Cell Model ◽  
Matrix Cracking ◽  
Element Analysis ◽  
Closed Form Solutions ◽  
Matrix Cracks ◽  
The Matrix ◽  
Interface Heat Transfer ◽  
Longitudinal Thermal Conductivity

The longitudinal thermal conductivity of a unidirectional fibre-reinforced composite containing an array of equally spaced transverse matrix cracks is calculated. The cracked composite is modelled by a cylindrical cell which accounts for altered heat transfer across the matrix cracks as well as through debonded portions of the fibre-matrix interface. Heat transfer mechanisms across the cracks and dedonded interfaces considered are contact, gaseous conduction, and radiation, and the relative importance of these mechanisms is discussed. Approximate closed form solutions to the cell model for the overall thermal conductivity are obtained using an approach reminiscent of the shear lag analysis of stiffness loss due to matrix cracking and debonding. Selected numerical results from a finite-element analysis of the cell model are presented to complement the analytical solutions. Both matrix cracking and interfacial debonding have the potential for significantly reducing the longitudinal thermal conductivity.

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