Nondestructive Characterization of Woven Fabric Ceramic Composites

Abstract

Woven fabric ceramic composites fabricated by the chemical vapor infiltration method are susceptible to high void content and inhomogeneity. The condition of such materials may be characterized nondestructively with ultrasonic methods. In this work, longitudinal and shear waves were used in the quantitative determination of elastic constants of NicalonTM/SiC composites as a function of volume percent of porosity. Elastic stiffness constants were obtained for both the inplane and out-of-plane directions with respect to fiber fabric. The effect of porosity on the modulus of woven fabric composites was also modelled and compared to the measured results. Scan images based on the amplitude and time-of-flight of radio frequency (RF) ultrasonic pulses were used for evaluating the material homogeneity for the purpose of optimizing the manufacturing process and for correlation with the mechanical testing results.

A Study on the Nondestructive Evaluation of Carbon/Carbon Brake Disks Using Ultrasonics

“…To obtain a quantitative, accurate value of the ultrasonic velocity, a pulse-overlap method with dry-coupling transducers was used [7]. These transducers contain an elastomer face layer and can be coupled by applying a pressure.…”

Tensile Fracture Behavior of Nicalon/SiC Composites

“…[18][19][20][27][28][29][30] X-ray CT is distinguished from conventional X-ray radiography by the view of creating a final image. X-ray CT is an advanced form of conventional X-ray radiography, that is, a conventional radiograph is a 2-D presentation of a three-dimensional object, and the image plane is approximately normal to the X-ray beam.…”

“…In this respect, X-ray CT is a useful technique to characterize the integrity of materials. [18][19][20][27][28][29][30] A typical level of slice thickness for X-ray CT is from 0.025 mm to 3 mm, with pixel sizes in the range of 0.025 mm to 1 mm. [27,31,32] In this research, all X-ray CT slices are 0.25 mm in thickness and 0.028 mm in pixel size.…”

“…[18][19][20][21][22] However, most work was focused on the characterization of CFCCs mainly using a single NDE technique, i.e., ultrasonic testing (UT), X-ray computed tomography (CT), or acoustic emission (AE). [18][19][20][21][22][23][24] Therefore, in this investigation, several different types of NDE techniques were employed for NDE of CFCCs. This investigation uses a combination of two NDE techniques, UT and X-ray CT, to provide precise characterization of the CFCC specimens prior to mechanical testing.…”

“…However, relatively little work has been performed on the investigation of micromechanisms of fracture in CFCCs using NDE techniques. [18][19][20] In this research, several NDE techniques, such as UT, X-ray CT, and infrared (IR) thermography, were used for CFCCs to characterize the fracture behavior before and during monotonic tensile loadings. Thus, the main objectives of this investigation on NDE and tensile behavior of continuous Nicalon fiber-reinforced SiC matrix composites (Nicalon/SiC) are to (1) apply NDE techniques for assuring the quality and structural integrity of CFCCs; (2) perform NDE using UT and X-ray CT methods for the analyses of defect distributions that may affect mechanical properties, before tensile testing;…”