Development and Applications of Nondestructive Methods for Predicting Mechanical Properties of Advanced Reinforced Nonmetallic Composites.
Interim technical rept. 1 Jun 70-30 Apr 71,
AVCO CORP LOWELL MASS SYSTEMS DIV
Pagination or Media Count:
A detailed evaluation of the interval velocity, one side access technique was conducted and results indicate that it has, at its present stage of development, a limited usefulness for routinely measuring relative values of polar velocity, and hence polar modulus, for many fiber reinforced composites including boronepoxy. Although the usefulness of nondestructive modulus measurements for predicting elastic modulus and ultimate strength for fiber composites has been confirmed, these studies strongly indicate that this capability can be extended to include all fiber configurations at any polar orientation. It has been shown that ultrasonic modulus affords a useful means for predicting yield strength in these boronepoxy composites, defined here as the point of departure from linearity on the stress-strain curve. Ultrasonic velocity measurements performed at various frequencies between 0.5 and 5.0 MHz following boronepoxy specimen loadings to successively higher strain levels only suggest, that 0.5 MHz measurements made in the thickness direction and possibly the length direction may be correlatable with the onset, or existence of degradation. Cursory analysis of ultrasonic energy transmission spectra at various frequencies suggests that the technique is very sensitive to changes in material characteristics, but its usefulness may be limited by the influence of extraneous variables. Work will continue using these techniques, as well as other in the pursuit of detecting degradation through non- destructive means. Author, modified-PL
- Laminates and Composite Materials
- Test Facilities, Equipment and Methods