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.

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 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.

Cumulative acoustic emission energy for damage detection in composites reinforced by carbon fibers within low-cycle fatigue regime at various displacement amplitudes and rates

2021 ◽  
pp. 096739112098570
Author(s):  
Mohammad Azadi ◽  
Mohsen Alizadeh ◽  
Seyed Mohammad Jafari ◽  
Amin Farrokhabadi
Keyword(s):  
Acoustic Emission ◽  
Carbon Fibers ◽  
Polymer Matrix Composites ◽  
Low Cycle Fatigue ◽  
Energy Parameter ◽  
Fatigue Tests ◽  
Matrix Cracking ◽  
Matrix Composites ◽  
Cycle Fatigue ◽  
Cumulative Energy

In the present article, acoustic emission signals were utilized to predict the damage in polymer matrix composites, reinforced by carbon fibers, in the low-cycle fatigue regime. Displacement-controlled fatigue tests were performed on open-hole samples, under different conditions, at various displacement amplitudes of 5.5, 6.0, 6.5 and 7.0 mm and also under various displacement rates of 25, 50, 100 and 200 mm/min. After acquiring acoustic emission signals during cycles, two characteristic parameters were used, including the energy and the cumulative energy. Obtained results implied that the energy parameter of acoustic emission signals could be used only for the macroscopic damage, occurring at more than 65% of normalized fatigue cycles under different test conditions. However, the cumulative energy could properly predict both microscopic and macroscopic defects, at least two failure types, including matrix cracking at first cycles and the fiber breakage at last cycles. Besides, scanning electron microscopy images proved initially such claims under all loading conditions.

Partial Strain Energy Release Rate for Study Matrix Cracking Evolution in Composite Cross-Ply Laminates

2015 ◽  
Vol 24 (3) ◽  
pp. 096369351502400
Author(s):  
Jean-Luc Rebière
Keyword(s):  
Stress Field ◽  
Composite Laminates ◽  
Strain Energy ◽  
Strain Energy Release Rate ◽  
Strain Energy Release ◽  
Matrix Cracking ◽  
Damage State ◽  
Damage Process ◽  
Cracking Mechanisms ◽  
Observed Damage

Matrix cracking is generally the first observed damage in composite laminates. The stress field distribution in the damaged cross ply laminates is analysed through an approach which uses several hypotheses to simplify the damage state. The proposed cracking criterion involves the respective partial part of the 0° and 90° layers to the damage process. The initiation of transverse and longitudinal cracking mechanisms is predicted.

On the Prediction of Damping in Composite and Sandwich Structures

2001 ◽  
Author(s):  
Victor Birman ◽  
Larry W. Byrd
Keyword(s):  
Composite Laminates ◽  
Loss Factor ◽  
Polymer Matrix Composites ◽  
Sandwich Structures ◽  
Free Vibrations ◽  
Matrix Composites ◽  
Analytical Evaluation ◽  
Numerical Examples ◽  
Mechanics Of Materials ◽  
Good Agreement

Abstract The paper outlines two methodologies for the analytical evaluation of the loss factor in composite laminates and in sandwich structures. One of these methods is based on the analysis of free vibrations, while the second approach utilizes mechanics of materials. The loss factor can be predicted both for specially orthotropic as well as for generally orthotropic laminae, subjected to axial stresses and/or transverse shear. The results for the loss factor of the laminae are in good agreement with available experimental data. As follows from numerical examples, the loss factor of polymer-matrix composites increases with the lamination angle and experiences relatively small variations at large values of these angles.

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