Crashworthiness of Corrugated Composite Shells
The increase of number of vehicles on the road has led to an increase in the traffic accidents. Consequently, there is also an increase of deaths and serious injuries. The desire to improve the crashworthiness of automobiles cannot be overestimated. It has been estimated that the annual financial...
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Format: | Thesis |
Language: | English English |
Published: |
2006
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Online Access: | http://psasir.upm.edu.my/id/eprint/163/2/549013_itma_2006_1_abstrak_je__dh_pdf_.pdf http://psasir.upm.edu.my/id/eprint/163/ |
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Summary: | The increase of number of vehicles on the road has led to an increase in the traffic
accidents. Consequently, there is also an increase of deaths and serious injuries. The
desire to improve the crashworthiness of automobiles cannot be overestimated. It has
been estimated that the annual financial loss from traffic accidents is equal to 2% of
the GNP of the USA. Together with a range of environmental concerns and social
pressure backed by legislation have led and continue to lead to highly innovative
designs, involving lighter materials such as composite materials. During the last
decades, researchers' interest have been directed towards the use of composite
structures for enhancing crashworthiness due to their superior properties, in
particular, strength and stiffness to weight ratios and their ability to be tailored in
composition and shape.
Of particular interest of this study is the use of corrugated composite shells in the
automobile industry as a crush energy absorber device. Extensive experimental and
computational programs have been conducted in order to investigate the crushing behaviour of corrugated and non-corrugated composite tubes. In the experimental
program, innovative mandrels and filament winding machine were designed and
fabricated. The investigated corrugated composite tubes consist of a number of
similar circular cones connected together by circular tubes in the order: conecylinder-
cone-cylinder and so on. The outer diameter of each tube is fixed at 100 mm
and the number of layers is maintained 6 layers. Two material types, namely,
filament wound carbon/epoxy and woven roving glass/epoxy were investigated.
A comprehensive quasi-static crushing test program was performed to examine the
influence of the tube length and the corrugation angle on the energy absorption
capabilities. The load-displacement curves and typical load paths together with
deformation histories were presented and discussed. The specific energy absorption,
energy absorption per unit length, crushing force efficiency and stroke efficiency
were calculated, analyzed and discussed. Comparisons in terms of specific energy
absorption and/or energy absorption per unit length capabilities between corrugated
composite and non-corrugated tubes were also presented and discussed. Macroscopic
photos were taken during the tests to help understanding the failure modes and the
failure mechanisms were analyzed microscopically.
The crushing load-displacement behaviour, energy absorption, and the observed
mechanisms and failure modes were found to be sensitive to the change in the
corrugation angle, the tube length and the fibre type, and distinct collapse modes
were observed. The most dominant observed failure modes are: catastrophic and
brittle fracture modes in filament wound carbon/epoxy tubes, progressive folding
mode (in the corrugated tubes) and splaying modes (in the non-corrugated tubes) of woven roving glass/epoxy tubes. Also splitting mode was observed in both filament
wound carbon/epoxy and woven roving glass/epoxy tubes. The results have shown
that corrugated composite tubes are efficient impact energy absorbers. Based on tube
length, GL3-0 and GL1-20 tubes experienced the highest energy absorption per unit
length (19.85, 18.89 kJ/m, respectively). Based on material type, filament wound
carbon/epoxy tubes exhibited higher specific energy than the corresponding woven
roving glass/epoxy tubes where 15.7 kJ/kg was absorbed by CL4-40 tube. Over all,
GL1-20 tubes could be recorded as the best choice for crashworthiness applications
(moderate load carrying capacity, high absorption energy, high CFE and high SE).
Concurrent with the experimental work, numerical analyses was carried out using
commercially available Finite Element Software (LUSAS). Three-dimensional
Linear buckling Finite Element was conducted for the corrugated and non-corrugated
composite tubes to predict the critical failure load, the deformation at the critical
load, and the stress concentration contours. Both the experimental and numerical
results were presented for different reinforcements, different corrugation angles, and
different tube lengths. Relatively, a reasonable agreement between the experimental
initial failure load and the computational critical load was obtained, specially for
corrugation angles = 30 and 40 degrees. Knockdown factor is used to compare the
results and found to be varying in the range from 0.259 (CL4-10) to 0.998 (GL4-40). |
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