LMA - Laboratoire de Mécanique et d’Acoustique

[Jeunes chercheurs] L. Thiercelin et A. Cocchi

Amphithéâtre François Canac, LMA

Le 10 mars 2020 de 11h00 à 12h00

- Aldo Cocchi (doctorant équipe M&S)
- Léo Thiercelin (doctorant équipe M&S)

Aldo Cocchi

Compressive behaviour in fibre direction and influence of matrix degradation in laminate composites

Abstract : Determination of compressive properties of fibre reinforced plastics (FRP) has always been a hot topic. Nowadays FRP are incrementally used even in everyday applications and properties underestimation can lead to components oversizing nullifying the main advantage of FRP.
Normally used compression testing techniques (ex. Celanese fixture, ASTM D3410) are designed to avoid specimen buckling to reach material failure. This is accomplished by reducing sample’s length. The drawback of this solution is the formation of stress concentrations and sample premature failure. To avoid this problem multiple tests have been proposed starting from variations of ASTM D3410 fixture to anti-buckling fixtures (ASTM D695) and indirect compression tests such as pure, three-points and four-points-bending [1, 2, 3].
In presence of tensile loadings, the main task of the matrix is to redistribute stresses between the fibers. Past studies show that extensive matrix damage or thermal degradation leads to reduction of the composite tensile strength [4, 5, 6]. This effect is even more important in presence of compressive loadings as the load bearing component of the material are slender elements with a natural tendency to buckle and fail, consequentially the polymeric matrix has also to support the fibres and avoid localized buckling.
The first part of this talk will be dedicated to compressive properties characterization. A novel four-pointsbending procedure will be presented together with the use of a flat hourglass specimen to reduce stress concentrations.
The second part will focus on the effect of matrix damage and thermal degradation on compressive strength. This will be done through the results of compressive tests on damaged samples and high temperature four-pointsbending.

References
[1] O. Montagnier, C. Hochard, Compression Characterization of High-modulus Carbon Fibers, Journal of Composite Materials 39 (1) (2005) 35–49. doi:10.1177/0021998305046433. URL http://journals.sagepub.com/doi/10....
[2] M. Serna Moreno, A. Romero Gutiérrez, J. Martìnez Vicente, Different response under tension and compression of unidirectional carbon fibre laminates in a three-point bending test, Composite Structures 136 (2016) 706–711. doi:10.1016/j.compstruct.2015.06.017. URL https://linkinghub.elsevier.com/ret...
[3] O. Allix, P. Ladevèze, E. Vittecoq, Modelling and identification of the mechanical behaviour of composite laminates in compression, Composites Science and Technology 51 (1) (1994) 35–42. doi:10.1016/0266-3538(94)90154-6. URL https://linkinghub.elsevier.com/ret...
[4] Y. Thollon, Analyse du comportement à rupture de composites stratifiés constitués de plis tissés sous chargements statique et de fatigue, PHD Thesis, Aix-Marseille Université (Dec. 2009).
[5] A. Gibson, M. O. Torres, T. Browne, S. Feih, A. Mouritz, High temperature and fire behaviour of continuous glass fibre/polypropylene laminates, Composites Part A : Applied Science and Manufacturing 41 (9) (2010) 1219– 1231. doi:10.1016/j.compositesa.2010.05.004. URL https://linkinghub.elsevier.com/ret...
[6] C. Hochard, S. Miot, Y. Thollon, Fatigue of laminated composite structures with stress concentrations, Composites Part B : Engineering 65 (2014) 11–16. doi:10.1016/j.compositesb.2013.10.020. URL https://linkinghub.elsevier.com/ret...

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