scholarly journals Application of the Equivalent Constraint Model to Investigate Stiffness Properties of Transversally Cracked and Split Frp Laminates

1999 ◽  
Vol 8 (5) ◽  
pp. 096369359900800 ◽  
Author(s):  
M. Kashtalyan ◽  
C. Soutis
Keyword(s):  
Matrix Cracking ◽  
Shear Lag ◽  
Transverse Cracks ◽  
New Approach ◽  
Shear Lag Model ◽  
Transverse Cracking ◽  
Stiffness Properties ◽  
Lag Model ◽  
Equivalent Constraint Model ◽  
Constraint Model

A new approach based on the Equivalent Constraint Model (ECM) [ 1 ] of the damaged lamina is applied to investigate the stiffness degradation in [0m/90n]s laminates due to matrix cracking both in the 90° (transverse cracking) and 0° (splitting) plies. The advantage of the approach is that it avoids cumbersome consideration of a repeated laminate element defined by the intersecting pairs of transverse cracks and splits, intrinsic to the earlier developed models [ 2 – 6 ]. Instead, two coupled problems for ECM laminates are solved. The stress field in the damaged lamina is determined by means of an improved 2-D shear lag analysis, and the reduced stiffness properties are described with the help of Insitu Damage Effective Functions, for which closed form expressions are obtained. Comparison of the new ECM/2-D shear lag model with the earlier developed models shows a reasonable agreement.

Evolution of Crack Density in Cross-Ply Laminates - Application of a Coupled Stress and Energy Criterion

2016 ◽  
Vol 713 ◽  
pp. 262-265
Author(s):  
Maria Kashtalyan ◽  
I.G. García ◽  
Vladislav Mantič
Keyword(s):  
Composite Laminates ◽  
Crack Density ◽  
Great Influence ◽  
Energy Criterion ◽  
Matrix Cracking ◽  
Transverse Cracks ◽  
Transverse Cracking ◽  
Finite Fracture Mechanics ◽  
Equivalent Constraint Model ◽  
Constraint Model

The first damage mode to appear in continuous fibre-reinforced composite laminates subjected to in-plane loading is usually transverse cracking, i.e. matrix cracking in the off-axis plies of the laminate. Since the density of transverse cracks has a great influence on the subsequent failure steps like delaminations, it is important to be able to predict it accurately. In this paper, the evolution of crack density with increasing external load is predicted using a combination of the Coupled Criterion of Finite Fracture Mechanics and the Equivalent Constraint Model.

scholarly journals A Study of Matrix Crack Tip Delaminations and their Influence on Composite Laminate Stiffness

1999 ◽  
Vol 8 (4) ◽  
pp. 096369359900800 ◽  
Author(s):  
Maria Kashtalyan ◽  
Costas Soutis
Keyword(s):  
Transverse Crack ◽  
Crack Density ◽  
Crack Tip ◽  
Implicit Functions ◽  
Transverse Cracks ◽  
Transverse Cracking ◽  
Stiffness Properties ◽  
Equivalent Constraint Model ◽  
Constraint Model ◽  
Stiffness Loss

Reduction of the stiffness properties of cross-ply [0m/90n]s laminates due to delaminations, growing at the 0/90 interface from the tips of transverse cracks in the 90° plies and splits in the 0° plies, is analysed by means of a theoretical approach based on the Equivalent Constraint Model (ECM). Reduced stiffness properties of the damaged lamina are derived as explicit functions of the crack density and relative delamination area associated with that lamina and implicit functions of the two damage parameters associated with the neighbouring laminae. Transverse crack tip delaminations are found to cause significant reduction in the laminate shear modulus and Poisson's ratio. Contribution of each damage mode (transverse cracking, transverse crack tip delaminations, splitting and split tip delaminations) into stiffness loss is established.

Analysis of Stresses for Cross-Ply Laminates with a Matrix Crack under Bending

2011 ◽  
Vol 284-286 ◽  
pp. 492-495
Author(s):  
Qing Dun Zeng ◽  
Mao Hua Ouyang
Keyword(s):  
Failure Mechanism ◽  
Transverse Crack ◽  
Approximate Solutions ◽  
Matrix Crack ◽  
Stress Distributions ◽  
Shear Lag ◽  
New Approach ◽  
Shear Lag Model ◽  
Lag Model ◽  
Shear Lag Theory

On the basis of the shear-lag theory, an analysis was presented for stress redistributions of cross-ply laminates with a transverse matrix crack in the 90º ply under bending by establishing a layered shear-lag model. The present results show that approximate solutions of displacement and stress distributions for cross-ply laminates with a transverse crack under bending can be obtained by using a shear-lag method. The present paper therefore affords a new approach for studying the stress redistributions and failure mechanism for cross-ply laminates with flaw under bending.

Analysis of Stresses for Cross-Ply Laminates with Multiple Matrix Cracks under Bending

2011 ◽  
Vol 311-313 ◽  
pp. 256-259
Author(s):  
Qing Dun Zeng ◽  
Mao Hua Ouyang
Keyword(s):  
Finite Element ◽  
Approximate Solutions ◽  
Stress Distributions ◽  
Shear Lag ◽  
Transverse Cracks ◽  
Shear Lag Model ◽  
Matrix Cracks ◽  
Variational Solutions ◽  
Lag Model ◽  
Good Agreement

On the basis of the shear-lag theory, a layered shear-lag model was established to study the stress redistributions of cross-ply laminates with multiple transverse matrix cracks in the 90º ply under bending. The present results are in a good agreement with variational solutions and finite element results and show that approximate solutions of stress distributions for cross-ply laminates with transverse cracks under bending can be obtained by using a shear-lag method. The present paper therefore affords a new way or method for studying the stress redistributions and failure mechanism for cross-ply laminates with flaws under bending.

Analysis of Fatigue Damage Mechanisms and Residual Properties of Polymer Matrix Composites

2000 ◽  
Author(s):  
Costas Soutis ◽  
Maria Kashtalyan
Keyword(s):  
Composite Laminates ◽  
Polymer Matrix Composites ◽  
Matrix Cracking ◽  
Matrix Composites ◽  
Residual Properties ◽  
Stiffness Properties ◽  
Observed Damage ◽  
Equivalent Constraint Model ◽  
Constraint Model ◽  
Longitudinal Cracks

Abstract Resin dominated damage modes such as matrix cracking in the off-axis plies and matrix crack-induced local and edge delaminations are common failure mechanisms in composite laminates under tensile or thermal fatigue. Accurate prediction of the laminate stiffness and strength must consider all the above-mentioned damage modes. In the present paper, an approach is developed for the analysis of cross-ply laminates damaged by transverse and longitudinal cracks and transverse and longitudinal delaminations that initiate and grow along these cracks. It is based on the Equivalent Constraint Model (ECM) of the damaged ply and employs an improved 2-D shear lag method to determine the stress field in the cracked and locally delaminated ply. The method is applied to predict residual stiffness properties of cross-ply graphite/epoxy laminates using experimentally observed damage patterns.

A Theory for Multi Damage Evaluation of TiN Thin Film

2000 ◽  
Vol 653 ◽  
Author(s):  
Kazunori Misawa ◽  
Tomonaga Okabe ◽  
Masaaki Yanaka ◽  
Masao Shimizu ◽  
Nobuo Takeda
Keyword(s):  
Thin Film ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Titanium Alloy ◽  
Tensile Load ◽  
Damage Evaluation ◽  
Shear Lag ◽  
New Approach ◽  
Shear Lag Model ◽  
Lag Model

AbstractThe present paper experimentally studies the cracking phenomena of a TiN thin film on a titanium alloy, and presents a new approach to predict the number of cracks under tensile load. An elastoplastic shear-lag model is developed to obtain the stress distribution caused by the film cracks, which is found to agree well with that calculated with FEM. The number of thin film cracks is predicted using a Monte Carlo simulation using the present approach, and favourably compared with the experimental results.

scholarly journals Exploration of Constants Independent of Material and Layup in Transverse Matrix Cracking of Cross-ply Laminate

1993 ◽  
Vol 2 (1) ◽  
pp. 096369359300200
Author(s):  
L-Y Xu
Keyword(s):  
Matrix Cracking ◽  
Crack Open Displacement ◽  
Shear Lag ◽  
Crack Open ◽  
Shear Lag Model ◽  
Stiffness Reduction ◽  
Longitudinal Stiffness ◽  
Lag Model ◽  
Open Displacement ◽  
Lamination Theory

Stiffness reduction caused by matrix crack in cross–ply laminates of CFRP, GFRP, KFRP can be predicted well by a shear–lag model assuming a constant of the crack open displacement index. Due to the existence of the saturation crack state (CDS), stiffness reduction has a low boundary, the minimum normalized longitudinal stiffness of the cracked plies is 0.3 instead of 0 used in current lamination theory on the behaviour prediction after FPF.

scholarly journals Modelling of stiffness degradation due to cracking in laminates subjected to multi-axial loading

2016 ◽  
Vol 374 (2071) ◽  
pp. 20160017 ◽  
Author(s):  
M. Kashtalyan ◽  
C. Soutis
Keyword(s):  
Structural Integrity ◽  
Axial Loading ◽  
Mode Interaction ◽  
Damage Mode ◽  
Shear Lag ◽  
Full Account ◽  
Matrix Cracks ◽  
Stiffness Properties ◽  
Equivalent Constraint Model ◽  
Constraint Model

The paper presents an analytical approach to predicting the effect of intra- and interlaminar cracking on residual stiffness properties of the laminate, which can be used in the post-initial failure analysis, taking full account of damage mode interaction. The approach is based on a two-dimensional shear lag stress analysis and the equivalent constraint model of the laminate with multiple damaged plies. The application of the approach to predicting degraded stiffness properties of multidirectional laminates under multi-axial loading is demonstrated on cross-ply glass/epoxy and carbon/epoxy laminates with transverse and longitudinal matrix cracks and crack-induced transverse and longitudinal delaminations. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’.

scholarly journals Stress Transfer from Axially Loaded Fiber to Matrix in a Microcomposite

1994 ◽  
Vol 365 ◽  
Author(s):  
Chun-Hway Hsueh
Keyword(s):  
Analytical Solutions ◽  
Volume Fraction ◽  
Axial Stress ◽  
Stress Transfer ◽  
Radial Dependence ◽  
Shear Lag ◽  
Shear Lag Model ◽  
The Matrix ◽  
Lag Model ◽  
Loaded Fiber

ABSTRACTThe shear lag model has been used extensively to analyze the stress transfer in a singe fiberreinforced composite (i.e., a microcomposite). To achieve analytical solutions, various simplifications have been adopted in the stress analysis. Questions regarding the adequacy of those simplifications are discussed in the present study for the following two cases: bonded interfaces and frictional interfaces. Specifically, simplifications regarding (1) Poisson's effect, and (2) the radial dependences of axial stresses in the fiber and the matrix are addressed. For bonded interfaces, the former can be ignored, and the latter can generally be ignored. However, when the volume fraction of the fiber is high, the radial dependence of the axial stress in the fiber should be considered. For frictional interfaces, the latter can be ignored, but the former should be considered; however, it can be considered in an average sense to simplify the analysis. Comparisons among results obtained from analyses with various simplifications are made.

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