Role of different fiber orientations and thicknesses of the skins and the core on the transverse shear damping of polypropylene honeycomb sandwich structures

Abstract

This paper investigates the effect of different orientations of fiber in the skins and different thicknesses of the skins and polypropylene honeycomb core (PPHC) on the transverse shear damping of the sandwich using experimental and theoretical studies. Three different sandwiches, SW1 (thickness of top and bottom FRP skin: 3.15mm each with 10mm thick PPHC), SW2 (thickness of top and bottom FRP skin: 1.575mm each with 5mm thick PPHC), SW3 (thickness of top and bottom FRP skin: 1.575mm each with 10mm thick PPHC) were fabricated for conducting experimental work. In order to study the effect of fiber orientation of the skin on the natural frequency and loss factors, five different orientations (all 0°, ±30°, ±45°, ±60° and all 90°) were considered. An impulse technique was used to calculate the natural frequency and loss factor of the composites. The natural frequency and loss factor were also computed theoretically and compared. As the in-plane load of the strong FRP skins imposes on the soft honeycomb core under dynamic condition, it causes a large transverse shear deformation on the core. This shear deformation leads to a high energy dissipation/loss factor of the sandwich. At the 0° fiber oriented sandwich, the loss factor value (η=0.0234) becomes significantly higher without losing its natural frequency (stiffness) value (fn=142.12Hz), which is not so in the case of FRP composites having the loss factor (η) value of 0.00218 and the natural frequency value (fn) of 114.23Hz. It is also found that the transverse shear effect and damping loss factor increases with the increase in the thicknesses of the skins and core of the sandwich.