The dynamic characteristics of fiber reinforced polymer skins with the alternate arrangement of continuous and chopped fibers on the polypropylene honeycomb core are investigated. It is envisaged that the damping could be improved by splitting the length of fiber into different short lengths so that more energy can be dissipated. The dynamic characteristics of FRP specimens with different forms of fibers were studied. The fibers were considered in the following five groups:, all continuous fibers, alternate arrangement of continuous and two chopped fibers, the same with three chopped fibers, four chopped fibers, and the five chopped fibers in. The natural frequencies and damping loss factors were evaluated by using the impulse technique with the half power band width method. The results revealed that for a given fiber volume fraction the damping could be improved by reducing the length of fibers. © (2014) Trans Tech Publications, Switzerland.

R. Velmurugan

Department of Aerospace Engineering

Damping

Fiber reinforced plastics

Interfaces (materials)

Nondestructive examination

Polypropylenes

Sandwich structures

CONTINUOUS FIBERS

DAMPING CHARACTERISTICS

DAMPING LOSS FACTOR

Dynamic characteristics

Fiber reinforced polymers

FIBER VOLUME FRACTIONS

POLYPROPYLENE HONEYCOMBS

VIBRATIONS

Fibers

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Advanced Materials Research

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: 3.15 mm each with 10 mm thick PPHC), SW2 (thickness of top and bottom FRP skin: 1.575 mm each with 5 mm thick PPHC), SW3 (thickness of top and bottom FRP skin: 1.575 mm each with 10 mm 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 (f<inf>n</inf> = 142.12 Hz), which is not so in the case of FRP composites having the loss factor (η) value of 0.00218 and the natural frequency value (f<inf>n</inf>) of 114.23 Hz. 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. © 2015 Elsevier Ltd. All rights reserved.

Mechanics of Materials

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

This paper reports the effect of temperatures (30°C to 80°C, with incremental steps of 5°C) 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. © The Author(s) 2015 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Journal of Reinforced Plastics and Composites

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

The effect of the chopped fibers on the damping characteristics of fiber reinforced polymer skins of the polypropylene honeycomb sandwich panel

Journal	Advanced Materials Research
Publisher	Trans Tech Publications
ISSN	10226680
Open Access	No