scholarly journals Delamination Buckling and Crack Propagation Simulations in Fiber-Metal Laminates Using xFEM and Cohesive Elements

2018 ◽  
Vol 8 (12) ◽  
pp. 2440 ◽  
Author(s):  
Davide De Cicco ◽  
Farid Taheri
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Hybrid Composites ◽  
Cohesive Elements ◽  
Zone Method ◽  
Fiber Metal Laminates ◽  
Finite Element Software ◽  
Numerical Predictions ◽  
Delamination Buckling ◽  
Fiber Metal

Simulation of fracture in fiber-reinforced plastics (FRP) and hybrid composites is a challenging task. This paper investigates the potential of combining the extended finite element method (xFEM) and cohesive zone method (CZM), available through LS-DYNA commercial finite element software, for effectively modeling delamination buckling and crack propagation in fiber metal laminates (FML). The investigation includes modeling the response of the standard double cantilever beam test specimen, and delamination-buckling of a 3D-FML under axial impact loading. It is shown that the adopted approach could effectively simulate the complex state of crack propagation in such materials, which involves crack propagation within the adhesive layer along the interface, and its diversion from one interface to the other. The corroboration of the numerical predictions and actual experimental observations is also demonstrated. In addition, the limitations of these numerical methodologies are discussed.

scholarly journals Use of Cohesive Elements in Fatigue Analysis

2007 ◽  
Author(s):  
Leonard J. Lucas ◽  
T. M. Black ◽  
D. P. Jones
Keyword(s):  
Finite Element ◽  
Fatigue Damage ◽  
Fatigue Crack Initiation ◽  
Pressure Vessels ◽  
Mathematical Representation ◽  
Cohesive Elements ◽  
Cohesive Law ◽  
Area Element ◽  
Finite Element Software ◽  
Cohesive Laws

Cohesive laws describe the resistance to incipient separation of material surfaces. A cohesive finite element is formulated on the basis of a particular cohesive law. Cohesive elements are placed at the boundary between adjacent standard volume finite elements to model fatigue damage that leads to fracture at the separation of the element boundaries per the cohesive law. In this work, a cohesive model for fatigue crack initiation is taken to be the irreversible loading-unloading hysteresis that represents fatigue damage occuring due to cyclic loads leading to the initiation of small cracks. Various cohesive laws are reviewed and one is selected that incorporates a hysteretic cyclic loading that accounts for energetic dissipative mechanisms. A mathematical representation is developed based on an exponential effective load-separation cohesive relationship. A three-dimensional cohesive element is defined using this compliance relationship integrated at four points on the mid-surface of the area element. Implementation into finite element software is discussed and particular attention is applied to numerical convergence issues as the inflection point between loading and unloading in the cohesive law is encountered. A simple example of a displacement-controlled fatigue test is presented in a finite element simulation. Comments are made on applications of the method to prediction of fatigue life for engineering structures such as pressure vessels and piping.

Finite Element Method and Analytical Studies on Fiber-Metal Laminates under Multiaxial Loadings

2017 ◽  
Vol 23 ◽  
pp. 63-71
Author(s):  
David J. Kvam ◽  
Yi Yu Duan ◽  
Erica Donnelly ◽  
Alicia Restrepo
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
High Strength ◽  
Finite Element Method Simulation ◽  
Fiber Metal Laminates ◽  
Composites Materials ◽  
Laminate Theory ◽  
Fiber Metal ◽  
High Strength Fiber ◽  
Element Method

Fiber-metal laminates (FMLs) are composites materials that are commonly used in areas such as aircraft industry. They are composed of ductile metal layers with high strength fiber reinforced polymer layers. So far, however, only uniaxial tests have been used to characterize the quasistatic mechanical properties, which cannot reflect the real loading situation of the FML applications. In this work biaxial tensile behavior of FMLs with glass and Kevlar fibers based on aluminum alloy is studied with finite element method simulation. The simulation is run to find the stress-strain relationship for FMLs at the off-axis angles of 0˚ and 45˚ for glass and Kevlar fibers. The “composites layups” are constructed for the 3D FML part. Two different elements C3D8R (8-node linear) and C3D20R (20-node quadratic) are used to carry out the simulation. The results show that C3D20R shows major advantages. Analytical solutions based on the classical laminate theory are obtained to compare with the finite element method (FEM) solutions. The results show good consistency.

Enhancement of performance of three-dimensional fiber metal laminates under low velocity impact – A coupled numerical and experimental investigation

2017 ◽  
Vol 21 (6) ◽  
pp. 2127-2153 ◽  
Author(s):  
Zohreh Asaee ◽  
Farid Taheri
Keyword(s):  
Three Dimensional ◽  
Absorption Capacity ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Fiber Metal Laminates ◽  
Velocity Impact ◽  
Finite Element Software ◽  
Fiber Metal ◽  
Time And Energy ◽  
The Impact

The main objective of the present study is to examine the level of enhancement in performance of three-dimensional fiber metal laminates (3DFML) under low velocity impact, when reinforced by different types of reinforcing face-sheets (i.e. fiberglass or carbon). Three layup configurations of the fabrics are considered in this investigation. The impact response of each of these configurations is assessed numerically using ABAQUS/Explicit, a commercially available finite element software. Specifically, each configuration’s impact capacity, deformation, contact time, and energy absorption capacity are evaluated. The numerical results are validated by comparison against experimental results. Moreover, a semi-empirical equation is developed for evaluating the impact capacity of such panels, as a function of impact energy, capable of accounting the influence of any type of reinforcement. Finally, the most efficient reinforced three-dimensional fiber metal laminates are identified based on their impact strength with respect to their overall weight and cost.

Benchmark of Finite Elements and Extended-Finite Elements Methods for Stress Intensity Factors and Crack Propagation

2018 ◽  
Author(s):  
Rémi Lacroix ◽  
Axelle Caron ◽  
Sandrine Dischert ◽  
Hubert Deschanels ◽  
Moïse Pignol
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Finite Elements ◽  
Crack Propagation ◽  
Stress Intensity Factors ◽  
Power Plants ◽  
Classical Case ◽  
Finite Elements Method ◽  
Intensity Factors ◽  
Numerical Predictions

Stress intensity factors (SIFs) are a major feature in regulatory analyses of Nuclear Power Plants (NPP) components, as they allow to rule on the acceptability of defects when compared to a critical experimental value (K1c). Simplified and robust evaluations of SIFs have been provided in major regulations standards for cracks having usual geometries and locations in major components. However, their evaluations still require a significant effort in the case of important deviations of the geometry of cracks regarding the usual semi-elliptical shape, or in the case of specific geometries of components, and specific locations of cracks in components. In these cases, time-consuming Finite Element meshes must be constructed, either manually or using semi-automatical tools, to represent the components and its defect(s). This method can become particularly costly, especially in the case of fatigue crack propagation. The eXtended-Finite Elements Method (X-FEM) has been proposed to overcome this issue. The representation of the defect is carried out by the level-set method, and specific enrichment functions are used to represent the solution near the crack surface and the crack front. This paper proposes a benchmark of numerical predictions of stress intensity factors using SYSTUS software [5]. It will be based on: a) Available analytical solutions; b) Classical Finite Element method; c) EXtended-Finite Elements Method. The classical case of a circular and elliptical crack in a semiinfinite body is first presented. Then the case of a circumferential crack in a valve under a thermo-mechanical loading is analyzed. The accuracy of the different methods is then compared and discussed.

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