QUANTITATIVE ANALYSIS OF THE DISTRIBUTION OF LOCAL POROSITY IN CARBON FIBER STRUCTURES BY LASER OPTOACOUSTIC METHOD

Abstract

Currently, an urgent problem is the development of non-destructive diagnostic techniques for quantifying the level of local porosity of composite structures. The paper presents a method for estimating the porosity of a material from the experimentally measured phase velocity of longitudinal acoustic waves propagating in it. Laser excitation of ultrasound was used to create probing pulses. Porosity was calculated using experimentally measured phase velocities of longitudinal acoustic waves propagating in the composite. The proposed method allows one-way access to the object during measurements, which makes it possible to study structures of variable thickness and complex shape. The possibility of obtaining distributions of local porosity values in the studied section of the structure is demonstrated by the example of three carbon fiber stringer panels. The study showed that locality of the porosity value and its change from point to point plays an important role in such constructions, and the maximum local porosity of this area of the panel may differ from the average volumetric porosity by more than two times. The possibility of obtaining a “map” of the distribution of the local porosity of the panel section in the plane of laying the carbon fabric is also demonstrated. This method is quite operational, which allows it to be used within the framework of real production in order to improve the conditions and methods of production.