Role of temperatures and fiber orientations on transverse shear damping of polypropylene honeycomb sandwich structures

This paper reports the effect of temperatures (30℃ to 80℃, with incremental steps of 5℃) and orientations of the glass fibers (0°, 30°, 45°, 60° and 90°) on the dynamic properties (the loss factors and the natural frequencies) of polypropylene honeycomb sandwich composites. The impulse technique has been employed to calculate the natural frequency and loss factor of the sandwich specimens under different temperatures. The natural frequency and loss factor values have also been calculated theoretically using Blevins's formulae for natural frequency, and Yim et al.'s transverse shear effect, respectively. The values of damping loss factor and the natural frequency/stiffness are the maximum at 0° fiber orientation in the skins of the sandwich specimen. The loss factor of the same oriented specimen increases sharply with the increase in temperature. The main reasons for the above are the higher in-plane strength of skins and lower transverse shear strength of the honeycomb core. Hence, the 0° fiber oriented sandwich specimen is more desirable than the other fiber oriented specimens at all temperatures. A good agreement is observed between the experimental and theoretical values.