Carbon/phenolic composite (CPC) materials are unique which consist of carbon fibers
embedded in a carbon matrix. The CPCs are originally developed for aerospace applications and its
low density, high thermal conductivity and excellent mechanical properties at elevated temperatures
make it an ideal material for aircraft brake disks. The properties of the CPC are dependent on the
manufacturing methods used for production and fiber arrangement. It is desirable to perform
nondestructive evaluation to assess material properties and part homogeneity in order to ensure
product quality and structural integrity of CPC brake disks. In this work, a CPC material was
nondestructively characterized and a technique was developed to measure ultrasonic velocity in C/P
composites using automated data acquisition software. Also a motorized system was adopted to
measure ultrasonic velocity on the point of CPC materials under the same coupling conditions.
Manual results were compared with those obtained by the motorized system with using drycoupling
ultrasonics and through transmission method in immersion. A peak-delay measurement
method well corresponded to ultrasonic velocities of the pulse overlap method and throughtransmission
mode and C-scan image signal based on peak-to-peak amplitude.
An Improved Antenna Group Delay Measurement Method Using a Three-antenna Extrapolation Technique
