Flash thermography with a periodic mask: profile evaluation of the principal diffusivities for the control of composite materials

Abstract

Fulfilment of the thermal properties for newly designed composite materials often requires that the thermal diffusivity in the principal directions is measured. In other instances, the measurement of in-plane diffusivity can give information on transverse defects like imbedded cracks. We present a flash thermography method for simultaneously imaging the through-thickness diffusivity and the in-plane diffusivity of anisotropic materials. It relies upon the use of a grid-like mask between the flash lamp and the inspected materials. Examples are presented for a two sided configuration. It enabled characterising the profile of the principal diffusivities in tensile samples and in carbon disk brakes.

Measurement of in-plane diffusivity in non-homogeneous slabs by applying flash thermography

“…As a matter of fact, by using a circular mask where the openings are regularly distributed over 360 • , one can evaluate simultaneously the through-thickness a z and the angular diffusivity a θ of a disk-shaped material. The non- destructive full-field characterisation of a carbon brake disk with this approach was described elsewhere [32].…”

Flash method experiment design for the thermal characterization of orthotropic materials

“…Regarding the front-face flash methods, most of them consider the case where an impulse is applied on the surface of the materials [5,9,10,12,[18][19][20]. Otherwise, some authors have investigated both rear-and front-face flash methods [15,[26][27][28], as does the present work.…”