ISSN:
1573-8922
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Results are presented from measurements of the velocity of longitudinal and shear elastic waves (f=5 MHz) in ÉD-20 epoxy resin, at temperatures from 4.2 to 293 K. These data were used to calculate the moduli of elasticity E′ and G′. Also, the moduli E′ (f=250 Hz) and G′ (f=2 Hz) of the ÉD-20 resin were measured directly. The calculated velocities of the low-frequency elastic waves ct=(E′/p)1/2 and ct=(G′/p)1/2 (where p is the density) were compared with the results from the ultrasonic measurements. The frequency dependence of elastic-wave velocity in the epoxy resin was evaluated. It was found that when the frequency was varied by four orders of magnitude, the dispersion of longitudinal-wave velocity was 18% at 4.2 K and 39% at 293 K. A quantitative criterion is proposed for estimation of the dispersion of sonic velocity from the results of measurements at any two frequencies. It was established that the sonic velocity at low temperatures varies linearly with the temperature, and in the case of longitudinal waves changes from cl-3360 m/sec at 4.2 K to 2820 m/sec at 293 K. The shear-wave velocity changes from ct=1630 m/sec at 5 K to 1340 m/sec at 293 K. The values of the dynamic Young's modulus E′ and shear modulus G′ at 4.2 K are 8.6 and 3.2 GPa, respectively. On a plot of c=f(T) for E′D-20, a transition is observed at 180 K, due to reorientational rotation of methyl groups. The activation energy of the relaxation process is 3.6 kcal/mole. Large values are obtained for the dispersion of the dynamic modulus E′:37.8% at 4.2 K and 93% at 293 K.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02254743
Permalink