| 1. |
- Govada, Anil K., et al.
(författare)
-
Acusto-ultrasonic measurements to minitor damage during fatigue of composistes
- 1984
-
Ingår i: 1984 advances in aerospace sciences and engineering. - New York : American Society of Mechanical Engineers. ; , s. 55-60
-
Konferensbidrag (refereegranskat)abstract
- An acousto-ultrasonic technique was used to monitor damage initiation and development in (0, 90//2)//s, (0, plus or minus 45)//s, and (0, 90, plus or minus 45)//s graphite epoxy laminates. The laminates were either loaded in quasi-static tension or were fatigued with tension-tension loading cycles. At a number of intermediate stages (strain levels for quasi-static tests and load cycles for the fatigue tests), the loading was halted and the acousto-ultrasonic measurements were made on the specimens. Several quantitative parameters, which include moments and ratios of moments of the frequency spectrum, were found to correlate extremely well with the stiffness change and the stress-strain behavior of the specimens.
|
|
| 2. |
- Talreja, Ramesh, et al.
(författare)
-
Quantitative assessment of damage growth in graphite epoxy laminates by acousto-ultrasonic measurements
- 1984
-
Ingår i: Review of progress in quantitative nondestructive evaluation. - New York : Plenum Publishing Co., N.Y.. - 306416786 ; , s. 1099-1106
-
Konferensbidrag (refereegranskat)abstract
- Composite materials fail by a complex development of many different damage modes, including matrix cracking, fiber-matrix debonds, delamination and fiber breakage. Nondestructive testing of composite materials must therefore concern itself with something other than the detection and geometrical location, sizing and orienting of single cracks. The acousto-ultrasonic techniques, developed by Vary, et al. , has the potential to respond to the development of damage states and to provide a quantitative parameter which monitors this damage development. This paper presents some preliminary data taken during quasi-static loading and fatigue of graphite epoxy laminates which indicate the plausibility of this statement. The ultrasonic signals received from transducers were amplified, digitized and stored in computer for later spectral analysis. A Fast Fourier Transform algorithm was used to perform spectral analysis. It is shown that the acousto-ultrasonic test is capable of sensitively monitoring the development of damage in graphite epoxy laminates
|
|
