Begell House Inc.
Composites: Mechanics, Computations, Applications: An International Journal
CMCA
2152-2057
5
3
2014
FE PROGRESSIVE FAILURE ANALYSIS OF ALL-GFRP PULTRUDED BEAM−COLUMN BOLTED JOINTS
173-193
10.1615/CompMechComputApplIntJ.v5.i3.10
Carlo
Casalegno
IUAV University of Venice, Dorsoduro 2206, 30123 Venice, Italy
Salvatore
Russo
Laboratory of Strength sof Materials, Department of Design in Complex Environment, Iuav University of Venice, Dorsoduro 2206, Convento delle
Terese, 30123 Venice, Italy
all-GFRP bolted joints
progressive failure analysis
finite element analysis
dissipation capacity
equivalent viscous damping
The paper presents the results of an FE progressive failure analysis of two all-GFRP pultruded beam−column bolted joints, aimed at evaluating the moment−rotation characteristics and the failure mechanisms. Different failure criteria are adopted in the analysis and the results are compared. The failure mechanisms and the moment−rotation characteristics of the joints are compared with those of similar pultruded connections. Finally, the dissipation capacity of the joints is investigated through the evaluation of the equivalent viscous damping for hysteretic cycles. The analysis results are presented, in particular, the capability of the analysis approach and of the adopted failure criteria to simulate the failure mechanism of the joints, especially if partially interactive criteria are adopted, that allow one to distinguish between the fibers and matrix failures. Also using the Tsai-Wu criterion failure initiation is detected in correspondence of the cleats' edges. The analysis of the joints subjected to hysteretic cycles points to the availability of some dissipation capacity related to the pseudo-ductile behavior of the joints induced by the damage progression. The adopted failure criteria give similar results for the joints subjected to pure bending, while significant differences are obtained for the joints subjected to the hysteretic cycles.
NUMERICAL CHARACTERIZATION OF ACRYLIC POLYMER UNDER QUASI-STATIC AND DYNAMIC LOADING BY IMPLEMENTING VISCOELASTIC MATERIAL MODEL
195-205
10.1615/CompMechComputApplIntJ.v5.i3.20
Uzair Ahmed
Dar
School of Mechanical Engineering, Northwestern Polytechnical University Xi'an, Shaanxi, China; Faculty of Mechanical Engineering GIK Institute of Engineering Sciences and Technology, Pakistan
mechanical behavior
material model
numerical simulation
strain rate
viscoelastic material
The mechanical response of poly-methyl-methacrylate (PMMA) acrylic polymer was numerically investigated under conditions of increased temperature and strain rate. PMMA is a highly strain rate- and temperature-sensitive polymer that can behave quite differently under different loading conditions. A temperature- and strain rate-dependent viscoelastic material model was employed to predict the quasi-static and dynamic behavior of this polymer at different temperatures and loading rates. The material model was implemented in an explicit finite element (FE) solver LS-DYNA by establishing a user defined material subroutine (UMAT). Finite-element models for low-strain rate uniaxial tensile test and high-strain rate split Hopkinson pressure bar (SHPB) compression test were built to verify the accuracy of the material subroutine. The results of simulations were compared with experimental results in terms of stress strain curves. Numerical results showed that the model successfully predicted the stress−strain behavior of PMMA at low and high strain rates as well as at elevated temperatures.
STRESS INTENSITY FACTOR FOR RADIAL CRACKS IN ROTATING HOLLOW FGM DISKS
207-217
10.1615/CompMechComputApplIntJ.v5.i3.30
Eskandari
Hadi
Abadan Institute of Technology, Petroleum University of Technology, Abadan, Iran
functionally graded materials
rotating disks
radial crack
stress intensity factor
The problem of stress intensity factor (SIF) investigation for radial cracks in a thin hollow rotating functionally graded material (FGM) disk is of utmost interest. The disk is assumed to be isotropic with exponentially varying elastic modulus in the radial direction. The crack length and material gradation are the main parameters to be studied. The critical values of stress intensity factors in homogeneous and FGM disks are obtained. The results show that the SIF is highly dependent on the crack length and material gradation.
STATIC FLEXURE OF CROSS-PLY LAMINATED CANTILEVER BEAMS
219-243
10.1615/CompMechComputApplIntJ.v5.i3.40
Yuwaraj M.
Ghugal
Department of Applied Mechanics, Government Engineering College, Karad-415124, Maharashtra State, India
Sangita B.
Shinde
Department of Civil Engineering, Jawaharlal Nehru Engineering College, Aurangabad-431001, Maharashtra, India
shear deformation
cross-ply laminated beam
layerwise trigonometric shear deformation theory
stress concentration
A static analysis of composite beams based on the layerwise trigonometric shear deformation theory is presented. The trigonometric sine function is used in the displacement field in terms of thickness coordinate to represent shear deformation. The present theory contains two displacement variables. The most important feature of the theory is that the transverse shear stress can be obtained directly from the constitutive relations that satisfy the stress-free boundary conditions at the top and bottom surfaces of the beam. Thus, the theory obviates the need for the shear correction factor. The governing equations and boundary conditions are obtained using the principle of virtual work. The unknown functions in the displacement field are determined from the general solution of linear governing differential equations. The transverse shear stresses are also obtained via two-dimensional equilibrium equations of the theory of elasticity. Two-layered (90°/0°) cross-ply laminated cantilever beams with different aspect ratios subjected to bending are examined. The results of flexural analysis are compared with those of the layerwise Bernoulli−Euler beam theory and the layerwise first-order shear deformation theory of Timoshenko.
FINITE-ELEMENT ASSESSMENT OF DAMAGE TO AN AIRCRAFT WINDSHIELD INCURRED BY HIGH-SPEED MULTIPLE BIRD STRIKES
245-258
10.1615/CompMechComputApplIntJ.v5.i3.50
Uzair Ahmed
Dar
School of Mechanical Engineering, Northwestern Polytechnical University Xi'an, Shaanxi, China; Faculty of Mechanical Engineering GIK Institute of Engineering Sciences and Technology, Pakistan
Weihong
Zhang
Laboratory of Engineering Simualtion and Aerospace Computing (ESAC), Northwestern Polytechnical University, P.O.Box 552, 710072, Xi'an, Shaanxi, China
AUTODYN
bird strike
finite-element model
high-speed impact
windshield
In this work, a numerical model has been developed to predict the damage and failure of an aircraft windshield incurred by high-speed repeated bird impacts. Finite element (FE) simulations were performed by implementing the numerical model in explicit FE solver ANSYS AUTODYN. A rate-dependent elastoplastic material model with the maximum principal stress failure criterion and Mie−Gruneisen equation of state (EOS) model with the tensile failure criterion were adopted to model the damage of windshield and bird, respectively. The model successfully predicts the damage initiation and complete failure of windshield at different impact velocities. The maximum normal displacement and equivalent stress at different positions on the windshield were determined and compared for a single and multiple impacts. On the basis of numerical results, the limiting impact velocity, critical number of impacts, and the weakest portion on the windshield were also determined. The results show that at higher impact velocity, multiple impacts prove fatal to the windshield structure. The windshield that withstands a single bird impact is vulnerable to fail under successive impacts.