Application of the Electronic Speckle Pattern Interferometry (ESPI) Technique for the Localisation Analysis of Damage Development in Composites

2002 ◽  
Author(s):  
Pascal J. P. Bouquet ◽  
Albert H. Cardon
Keyword(s):  
Polymer Matrix ◽  
Polymer Matrix Composites ◽  
Electronic Speckle Pattern Interferometry ◽  
Strength Analysis ◽  
Creep Recovery ◽  
Matrix Composites ◽  
Damage Development ◽  
Damage Initiation ◽  
Delayed Failure

The analysis of the long-term behaviour of polymer matrix composites has to be performed for their stiffness evolution and for their strength changes. Long fiber reinforced polymer matrix composites exhibit an anisotropic viscoelastic-viscoplastic behaviour. The non-linear viscoelastic constitutive equations proposed by R. Schapery [1], with a viscoplastic correction are able to analyse the long-term stiffness evolution on the basis of some short-term creep and creep-recovery tests. For the strength analysis it is possible to consider some delayed failure approach as the end of a viscoelastic-viscoplastic behaviour. The experimental follow-up of the creep evolution till rupture needs a full field technique in order to have a complete view of the strain field and the evolution of this field where the damage initiation and development transforms the homogeneous strain distribution in an heterogeneous one. The ESPI technique shows clearly the location of the damage initiation and allows us to follow the damage development. Examples of the ESPI technique on graphite epoxy specimen will be presented and the results in relation to the delayed failure analysis will be discussed.

scholarly journals Fatigue Damage Characterization of Braided and Woven Fiber Reinforced Polymer Matrix Composites at Room and Elevated Temperatures

2021 ◽  
Author(s):  
John Montesano
Keyword(s):  
Elevated Temperature ◽  
Prediction Model ◽  
Fatigue Damage ◽  
Polymer Matrix ◽  
Elevated Temperatures ◽  
Polymer Matrix Composites ◽  
Stiffness Degradation ◽  
Woven Composites ◽  
Matrix Composites ◽  
Damage Development

The use of polymer matrix composites (PMC) for manufacturing primary load-bearing structural components has significantly increased in many industrial applications. Specifically in the aerospace industry, PMCs are also being considered for elevated temperature applications. Current aerospace-grade composite components subjected to fatigue loading are over-designed due to insufficient understanding of the material failure processes, and due to the lace of available generic fatigue prediction models. A comprehensive literature survey reveals that there are few fatigue studies conducted on woven and braided fabric reinforced PMC materials, and even fewer at elevated temperatures. It is therefore the objective of this study to characterize and subsequently model the elevated temperature fatigue behaviour of a triaxial braided PMC, and to investigate the elevated temperature of fatigue properties of two additional woven PMCs. An extensive experimental program is conducted using a unique test protocol on the braided and woven composites, which consists of static and fatigue testing at various test temperatures. The development of mechanically-induced damage is monitored using a combination of non-destructive techniques which included infrared thermography, fiber optic sensors and edge replication. The observed microscopic damage development is quantified and correlated to the exhibited macroscopic material behaviour at all test temperatures. The fiber-dominated PMC materials considered in this study did not exhibit notable time or temperature-dependent static properties. However, fatigue tests reveal that the local damage development is in fact notably influenced by temperature. The elevated temperature environment increases the toughness of the thermosetting polymers, which results in consistently slower fatigue crack propagation rates for the respective composite materials. This has a direct impact on the stiffness degradation rate and the fatigue lives for the braided and woven composites under investigation. The developed analytical fatigue damage prediction model, which is based on actual observed damage mechanisms, accurately predicted the development of damage and corresponding stiffness degradation for the braided PMC, for all test temperatures. An excellent correlation was found between the experimental the predicted results to within a 2% accuracy. The prediction model adequately captured the local temperature-induced phenomenon exhibited by the braided PMC material. The results presented in this study are novel for a braided composite material subjected to elevated temperature fatigue.

Long-term durability of polymer matrix composites under hostile environments

2005 ◽  
Vol 412 (1-2) ◽  
pp. 159-164 ◽  
Author(s):  
H. Kawada ◽  
A. Kobiki ◽  
J. Koyanagi ◽  
A. Hosoi
Keyword(s):  
Polymer Matrix ◽  
Polymer Matrix Composites ◽  
Matrix Composites ◽  
Hostile Environments
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