Nondestructive investigation of damage in composites using x-ray tomographic microscopy (XTM)

Abstract

X-ray tomographic microscopy (XTM), utilizing intense, highly collimated synchrotron radiation, has been used to nondestructively image materials structures in three dimensions. The spatial resolution of the technique approaches that of conventional optical microscopy, but XTM does not require polished surfaces or serial sections. We present the results of an XTM investigation of a composite material composed of silicon-carbide fibers in an aluminum matrix. The results reveal the aluminum/silicon-carbide interfaces and show microcracks running along many of the interfaces as well as in the matrix. Excellent contrast is observed between the silicon-carbide sheath of the fiber surrounding the graphite core and the coating at the fiber-matrix interface. The sensitivity to small changes in the linear absorption coefficient allows nondestructive imaging of variations in chemistry between graphite and silicon carbide and between silicon carbide and aluminum. The experimentally determined values of the absorption coefficients of these phases are identical to values published in the literature. For the first time, XTM will allow observation of damage accumulation and crack growth during deformation testing. The availability of such data will greatly improve our understanding of failure in advanced materials.

MicroCT (microtomography) quantification of microstructure related to macroscopic behaviour: Part 2 – Damage in SiC–Al monofilament composites tested in monotonic tension and fatigue

“…The mean linear attenuation coefficients of the Al matrix, the SiC portions of the fibres and the carbon fibre cores agreed closely with what was expected; averaging over a number of slices allowed the radial variation in SiC composition to be detected. 6 These aspects have been discussed in detail previously, as cited above and these aspects will not be mentioned further. Figure 1 showed a typical tensile stress-strain curve for the SiC-Al coupons.…”

Microtomography: A tool for nondestructive study of materials

“…One of the most promising applications for microtomography will be in the fields of composites (4). Figure 3 shows a section of a tomographic reconstruction of A1 2 O 3 fiber reinforced aluminium, and compares its spatial resolution with a SEM image of a polished surface of the same material.…”

Diffraction microcomputed tomography of an Al-matrix SiC-monofilament composite

“…This paper reports high-energy X-ray diffraction microCT of an Al-matrix SiC-monofilament-reinforced composite. The study employs a well characterized batch of materials (via three-dimensional absorption microCT and supporting techniques) (Kinney et al, 1990;Breunig, 1992;Breunig et al, 1993Breunig et al, , 2006 to extend diffraction tomography beyond the earlier studies, specifically to establish the accuracy of crystallographic phase mapping and to examine the effects of crystallographic texture.…”