Experimental and simulation study of energy absorption capability of foam-filled Nomex honeycomb structure /
This research work proposes to increase the energy absorption capability of honeycomb structure by strengthening its cell walls. As the cell walls are strengthened, they will not buckle at the very beginning of compression loading, thus contribute in taking the compression load as well. One of the p...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
Kuala Lumpur :
Kulliyyah of Engineering, International Islamic University Malaysia,
2014
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| Subjects: | |
| Online Access: | Click here to view 1st 24 pages of the thesis. Members can view fulltext at the specified PCs in the library. |
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| Summary: | This research work proposes to increase the energy absorption capability of honeycomb structure by strengthening its cell walls. As the cell walls are strengthened, they will not buckle at the very beginning of compression loading, thus contribute in taking the compression load as well. One of the possible ways to do it is by putting light weight material such as polyurethane foam inside the honeycomb cells. The choice of foam material is based on the availability of data in the literature in term of its behavior under compression loading, its fabrication process and its capability in absorbing energy due to its large plastic deformation. The proposed foam-filled honeycomb structure, unfilled honeycomb and polyurethane foam are subjected to quasi-static compression loading with constant strain rate of 0.05 per second. The peak force and energy absorption of foam-filled honeycomb are analyzed to study its increment compared to the summation of its individual components (unfilled honeycomb and foam alone). The effects of polyurethane foam's density, Nomex honeycomb's density, height and cell numbers on the two mentioned properties are investigated. From experimental results, the peak force and energy absorption are increased up to 63% and 67% respectively, if compared to the summation of individual components, which proves that the foam strengthens the cell walls. Its failure mechanism consists of foam densification at locations of wall buckling, change of boundary conditions from free-free to fixed-fixed at both ends, fill-up of the folded walls by foam, action of the filled foam as a crushable mandrel, closing of the wall opening by foam compression in adjacent cells, and more stable outer cells which allows fold formation of the cell walls. The foam density hardly influences the peak force but increases slightly the energy absorption. Therefore, it seems that the foam only plays a role to strengthen the cell walls of honeycomb. Higher honeycomb's density, shorter height and higher number of cells are preferable to achieve higher peak force and energy absorption. Study of the interaction between foam and cell walls is carried out further using FEA simulation. Since both loading and boundary conditions are symmetrical, the honeycomb part of unfilled and foam-filled honeycomb is modeled as one corner of honeycomb structure which has three connected walls. The corner represents the symmetrical geometry of unfilled and foam-filled honeycomb structure. As for foam alone, symmetrical model of a quarter of actual foam is used. A good correlation is found between experimental and computation results for the three structures. From simulation results, analysis of distribution of energy between vertical edge/cell walls and foam of the foam-filled honeycomb is possible. It is found that wall buckling is initiated in the middle structure due to the change of boundary condition, and the foam fills-up the folds, which in turn strengthen the cell walls. |
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| Physical Description: | xix, 197 leaves : ill. ; 30cm. |
| Bibliography: | Includes bibliographical references (leaves 171-173) |