Evaluation of transverse elastic properties of fibers used in composite materials by laser resonant ultrasound spectroscopy

Denis Mounier , Christophe Poilâne (1) , Cécile Bûcher , Pascal Picart (2)

1 LRPMN - Laboratoire de recherche sur les propriétés des matériaux nouveaux
2 LAUM - Laboratoire d'Acoustique de l'Université du Mans

We evaluate the elastic properties of glass, carbon, and flax fibers that are used to manufacture composite materials. The transverse elastic properties of fibers are more difficult to measure than the longitudinal properties. But the knowledge of the transverse properties is mandatory to predict correctly the mechanical behavior of a composite material. We apply the laser resonant ultrasound spectroscopy (RUS) technique to evaluate the transverse Young modulus and Poisson ratio of fibers. The mechanical vibrations of a cross section are generated by a pulsed subnanosecond laser beam focused and shaped on the fiber as a line parallel to the fiber. The vibrations are detected optically by the probe beam of an interferometer, focused at the zone of excitation. The measured eigenfrequencies range from 5 MHz for flax fibers to 500 MHz for carbon and glass fibers. Using finite element modeling, the eigenmodes of fibers are identified and the mechanical properties of the fiber materials are evaluated. The transverse elastic properties of carbon fibers are significantly different from the longitudinal properties. For flax fibers, the strong damping of modes which is observed could explain the strong damping of flax fiber reinforced polymers.

Mots clés: Resonant ultrasound spectroscopy; laser ultrasonics; vibration modes; composite materials

Domaines: Acoustique [physics.class-ph]

Denis Mounier, Christophe Poilâne, Cécile Bûcher, Pascal Picart. Evaluation of transverse elastic properties of fibers used in composite materials by laser resonant ultrasound spectroscopy. Acoustics 2012, Apr 2012, Nantes, France. ⟨hal-00811303⟩