engleski

Caustics in Graphite Fiber-Reinforced Materials

This contribution deals with the application of the optical method of caustics to the non transparent mechanically anisotropic materials. The size of a caustic curve depends on the optical conditions and load intensity applied to the specimen. The necessity of the numerical simulations of the singular caustic curves, which are of different shape for each situation separately (mechanical characteristics, position of the crack, mixed-mode crack opening ratio), is explained by reasons of proper evaluation of experimental results. The application is shown for the representative type of graphite fiber reinforced composite material. The experimental determination of the stress intensity factors K, e. g. K, and K", is simultaneously performed by measuring the maximum dark spot diameters and by using the advanced multi-point over-deterministic data reduction method. The experimental equipment, that consists of the point light source of high energy, lenses and CCD camera with AD converter and computer, makes possible the filtering of the image and better recognition of the dark zone boundary.

fracture mechanics; experimental method of caustics; graphite fiber-reinforced materials

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