MICROMECHANICAL FINITE ELEMENT PREDICTION OF INTERLAMINAR TRACTION-SEPARATION LAWS USING J-INTEGRAL APPROACH

2021 ◽  
Author(s):  
CHRISTOPHER S. MEYER ◽  
BAZLE Z. HAQUE ◽  
DANIEL J. O’BRIEN ◽  
OHN W. GILLESPIE, JR.
Keyword(s):  
Finite Element ◽  
Composite Laminates ◽  
Element Model ◽  
Unidirectional Composite ◽  
Woven Composites ◽  
Cohesive Zone Modeling ◽  
Integral Approach ◽  
J Integral ◽  
Dynamic Impact ◽  
Transverse Cracks

Dynamic impact loading of woven composites leads to mesoscale damage such as interlaminar transverse cracks and intralaminar tow-tow delamination cracks. At the microscale, this damage may be modeled as fracture between [90/90] and [0/90] unidirectional composite laminates. Microscale finite element model (FEM) resolution of dynamic impact at structural length scale is intractable, but mesoscale FEM resolution is possible with current computational resources. However, mesoscale cohesive zone modeling of this damage requires appropriate tractionseparation laws. These laws are predicted in this work with fiber length-scaleresolved FEMs, which include residual stress, experimentally measured, ratedependent, nonlinear matrix behavior, and experimentally measured, computationally validated, rate-dependent fiber-matrix interface properties. The J-integral from elastoplastic fracture mechanics is computed under mode I and mode II loading and differentiated to determine the traction-separation laws.

Cohesive Finite Element Based Modeling of Damage in Composite Materials

2002 ◽  
Author(s):  
Rajesh S. Kumar ◽  
Ramesh Talreja
Keyword(s):  
Finite Element ◽  
Composite Materials ◽  
Composite Laminates ◽  
Damage Evolution ◽  
Crack Density ◽  
Cohesive Zone Modeling ◽  
Cohesive Law ◽  
Transverse Cracks ◽  
Damage State ◽  
Viscoelastic Composite

Damage in composite laminates affects its overall viscoelastic response. Constitutive equations have been developed for composite laminates considering a fixed damage state. A complete description, however, requires suitable damage evolution laws. This paper is focused on studying damage evolution in viscoelastic laminates using a cohesive finite element approach. A two dimensional, four nodded finite element is developed incorporating a rate-independent traction-displacement cohesive law. This element is used in conjunction with plane strain bulk elements behaving in a linear viscoelastic manner to simulate crack evolution between two existing transverse cracks in symmetric cross-ply laminates. The effects of loading strain-rate, ply constraint and initial crack density are studied. This study shows expected trends in the behavior and indicates the suitability of cohesive zone modeling to study damage evolution in viscoelastic composite materials.

Dynamic Impact Measurements on Crossings, in Free Floating and In-Situ Conditions

2014 ◽  
Author(s):  
M. A. Boogaard ◽  
A. L. Schwab ◽  
Z. Li
Keyword(s):  
Finite Element ◽  
Condition Monitoring ◽  
Impact Loading ◽  
Dynamic Behaviour ◽  
Element Model ◽  
Mode Shapes ◽  
Dynamic Impact ◽  
In Situ Test ◽  
In Situ Conditions

As vibration based condition monitoring requires a good understanding of the dynamic behaviour of the structure, a good model is needed. At the TU Delft a train borne monitoring system is being developed which currently focusses on crossings. Crossings are prone to very fast degradation due to impact loading. In this paper a finite element model of a free floating frog is presented and validated up to a 100 Hz using dynamic impact measurements. The mode shapes of the free floating frog are then also compared to some preliminary results from an in-situ test. This comparison shows that the in-situ frequencies can be up to twice the free floating frequency.

Evaluation of Adhesive Joints of Two Different Materials

2012 ◽  
Author(s):  
M. M. Islam ◽  
Rakesh K. Kapania
Keyword(s):  
Finite Element ◽  
Dissimilar Materials ◽  
Element Model ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Cohesive Zone Modeling ◽  
Stress Distributions ◽  
Test Fixture ◽  
Zone Modeling ◽  
Nonlinear Finite Element Model

In a test-fixture that the authors were using, steel tabs adhesively bonded to an aluminum panel debonded before the design load on the real test panel was fully applied. Therefore, studying behavior of adhesive joints for joining dissimilar materials was deemed to be necessary. To determine the failure load responsible for debonding of adhesive joints of two dissimilar materials, stress distributions in adhesive joints as obtained by a nonlinear finite element model of the test-fixture were studied under a gradually increasing compression-shear load. It was observed that in-plane stresses were responsible for the debonding of the steel tabs. To achieve a better understanding of adhesive joints of dissimilar materials, finite element models of adhesive lap joints and Asymmetric Double Cantilever Beam (ADCB) were studied, under loadings similar to the loading faced by the test-fixture. The analysis was performed using ABAQUS, a commercially available software, and the cohesive zone modeling was used to study the debonding growth.

scholarly journals Characterization of Adhesives Bonding in Aircraft Structures

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4816
Author(s):  
Maria Grazia Romano ◽  
Michele Guida ◽  
Francesco Marulo ◽  
Michela Giugliano Auricchio ◽  
Salvatore Russo
Keyword(s):  
Finite Element ◽  
Composite Material ◽  
Finite Element Model ◽  
Impact Energy ◽  
Element Model ◽  
Cohesive Zone Modeling ◽  
Main Task ◽  
Opening Displacement ◽  
Lap Shear ◽  
The Impact

Structural adhesives play an important role in aerospace manufacturing, since they provide fewer points of stress concentration compared to faster joints. The importance of adhesives in aerospace is increasing significantly because composites are being adopted to reduce weight and manufacturing costs. Furthermore, adhesive joints are also studied to determine the crashworthiness of airframe structure, where the main task for the adhesive is not to dissipate the impact energy, but to keep joint integrity so that the impact energy can be consumed by plastic work. Starting from an extensive campaign of experimental tests, a finite element model and a methodology are implemented to develop an accurate adhesive model in a single lap shear configuration. A single lap joint finite element model is built by MSC Apex, defining two specimens of composite material connected to each other by means of an adhesive; by the Digimat multi-scale modeling solution, the composite material is treated; and finally, by MSC’s Marc, the adhesive material is characterized as a cohesive applying the Cohesive Zone Modeling theory. The objective was to determine an appropriate methodology to predict interlaminar crack growth in composite laminates, defining the mixed mode traction separation law variability in function of the cohesive energy (Gc), the ratio between the shear strength τ and the tensile strength σ (β1), and the critical opening displacement υc.

Effect of Compressive and Shear Deformation of 2.5D Preform on its Stiffness of Composites

2019 ◽  
Vol 943 ◽  
pp. 75-80
Author(s):  
Fang Bin Lin ◽  
Ying Dai ◽  
Han Yang Li ◽  
Yang Qu ◽  
Wen Xiao Li
Keyword(s):  
Finite Element ◽  
Shear Deformation ◽  
Cell Model ◽  
Deformation Mode ◽  
Element Model ◽  
Tensile Tests ◽  
Woven Composites ◽  
Forming Process ◽  
Element Analysis ◽  
Plane Shear

Transverse compaction and in-plane shear deformartion are the dominative deformation mode for woven preform during forming process. A full finite element model of the 2.5D woven composites has been established by the computed tomography (CT) in this paper. Based on the energy method, the effective orthotropic/anisotropic stiffness coefficientsCijare calculated by performing a finite element analysis (FEA) of this full cell model. Using this model, the effects of the compaction and shear deformation of the 2.5D woven preform on the composites stiffness are investigated in detail. Compared the results of the static tensile tests, the rationality of the model and the method is verified.

Finite Element Fracture Mechanics Study of Pre-Northridge Connections

2006 ◽  
Vol 324-325 ◽  
pp. 1007-1010 ◽  
Author(s):  
Hong Bo Liu ◽  
Chang Hai Zhai ◽  
Yong Song Shao ◽  
Li Li Xie
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Fracture Behavior ◽  
Integral Approach ◽  
J Integral ◽  
Finite Element Analyses ◽  
Element Analysis ◽  
Weld Root

The objective was to quantify the variation of stress intensity factor to weld root flaw sizes in steel frame connections. Finite-element analyses were used to study fracture toughness in welded beam-column connections. Investigations of fracture behavior mainly focused on the standard pre-Northridge connection geometry. Finite element analysis was performed using the ANSYS computer program. Stress intensity factor was calculated through a J-integral approach. Results show that stress intensity factor is not uniform and is largest in the middle of beam flange. Stress intensity factor increases nearly linear with the increase of flaw size. Backing bars have little effect on weld fractures.

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