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Research Papers

Study of Far-Field Pyroshock Responses of Composite Panels

[+] Author and Article Information
R. Velmurugan

Department of Aerospace Engineering,
Indian Institute of Technology Madras,
Chennai Tamilnadu 600036, India
e-mail: ramanv@iitm.ac.in

E. Mohamed Najeeb

Department of Aerospace Engineering,
Indian Institute of Technology Madras,
Chennai Tamilnadu 600036, India

Contributed by the Technical Committee on Vibration and Sound of ASME for publication in the JOURNAL OF VIBRATION AND ACOUSTICS. Manuscript received December 4, 2012; final manuscript received March 17, 2014; published online April 9, 2014. Assoc. Editor: Olivier A. Bauchau.

J. Vib. Acoust 136(3), 031014 (Apr 09, 2014) (10 pages) Paper No: VIB-12-1338; doi: 10.1115/1.4027223 History: Received December 04, 2012; Revised March 17, 2014

The experimental and numerical studies on far-field pyroshock responses of composite panels are presented in this paper. The purpose of this study is to find out the region of composite panel where the pyroshock response is high and thereby the panel can be used as a testing bed to examine tiny elements such as electronic parts used in spacecraft. Experiments based on bi-plate technology are conducted on different combination of e-glass/epoxy composite panel parameters. The structural responses are analyzed using panel parameters as well as shock response spectrums (SRSs) computed from the acceleration-time histories. The experiments are carried out for a low range of chamber pressure with projectiles of varying length to get the far-field response of the test panel. The accelerations of the panel at selected locations are measured by the PCB Piezotronics (Depew, NY) accelerometers and National Instruments-Data Acquisition (NI-DAQ) system (National Instruments, Austin, TX) with labview software. Finite element analysis (FEA) for the pyroshock environment is done using abaqus/Explicit software. Due to the symmetry of the structure as well as the loading, only quarter portion of the panel is analyzed. From the results, it is found that acceleration increases as thickness of composite test panel increases (about 20–70%) for all the combinations of projectile length and chamber pressure at all the points considered on the laminate. Transfer of acceleration from steel plate onto composite panel through physical connections is predominant (about 90–95% of total transfer) than that through air media between the steel plate and the composite panel. Velocity with lower momentum induces lower frequency modes to be dominant whereas velocity with higher momentum induces higher frequency modes. Normally higher accelerations (about 40–90%) are experienced at the center location than any other locations under consideration. The SRSs are obtained both from FEA and experiments. The experimental study shows good agreement with the FEA results both in acceleration time history as well as in SRS.

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References

Figures

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Fig. 1

Experimental pyroshock test setup

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Fig. 2

Test specimen fixture

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Fig. 3

Numerical modeling details of plates

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Fig. 4

Locations for accelerometers on the composite panel

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Fig. 5

Schematic diagram of acceleration distribution on to composite panel

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Fig. 6

Distribution of acceleration on composite panel

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Fig. 7

Effect of laminate thickness on acceleration

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Fig. 8

Effect of projectile velocity on acceleration

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Fig. 9

Effect of locations on acceleration

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Fig. 10

Modal distribution on accelerometer locations

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Fig. 11

Acceleration time histories

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Fig. 12

Shock response spectrum model

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Fig. 13

Free body diagram of SDOF system

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Fig. 14

Shock response spectrums at Q = 10

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Fig. 15

FRF plot for 3 layer laminate at projectile velocity 23.3 m/s

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