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Title:	Crashworthiness characteristics of woven ramie/bio-epoxy® composite tubes in quasi-static compression
Authors:	Majid Jafarzadehghoushji (P69998)
Supervisor:	Che Husna Azhari, Prof. Dr.
Keywords:	Automobiles -- Crashworthiness Tubes Composite materials Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia
Issue Date:	6-Oct-2019
Description:	Using metallic materials in automotive structures increases weight, fuel consumption and cost, therefore, certain trends have begun to use lightweight cheaper and bio materials. This study evaluated the crashworthiness characteristics of woven ramie bio-epoxy® composite square tubes as energy absorbers. Composite laminate specimens were subjected to static axial compression load and evaluated experimentally for energy absorption capability. Specimens were prepared with square cross-sections (80 mm × 80 mm) and a radius curvature of 5 mm. Besides non-trigger mechanism, external trigger mechanism was employed in axial quasi-static compression test of the composite tubes to induce progressive failure to the specimens. In this study, variables were tube length, namely, 50, 80, and 120 mm. The thickness of the walls, which consist of ramie bio-epoxy® laminates, was also varied according to the number of layers, i.e., 12, 24, and 30 layers, corresponding to equivalent wall thickness of 1.7, 3.4, and 4.2 mm, respectively. The parameters measured were total absorbed energy (Etotal) and crush force efficiency (CFE). Etotal is the measure of the amount of energy that the structure can absorb during collision, thus being a measure of strength. CFE provides a quantitative indication of the mode of failure of the composites. The mode of failure was observed by photography. In the axial compression test of woven ramie bio-epoxy® composite square tubes, nontriggered specimens exhibited catastrophic failure. In particular, 120-mm long specimens with 12 and 24 layers failed in local buckling, which was initiated at the edges, followed by buckling and collapse. For the rest of the samples, mid length buckling was observed, which failure was initiated at the middle of the tubes, and then proceed to overall buckling and catastrophic failure. Results showed that the highest value of Etotal (3.38 kJ) was obtained for 120-mm long specimens with 30 layers of ramie bio-epoxy® laminates, whereas the maximum value for CFE (0.31) was obtained in the 80-mm long specimen with 24 layers of ramie bio-epoxy® laminates. However, under the quasi-static axial compression tests, the triggered specimens exhibited progressive failure. The triggered specimens failed in local buckling except the 80-mm long specimens with 12 and 24 layers. Results showed that the highest values of Etotal were obtained for 120-mm long specimens with 30 layers of ramie bioepoxy® laminates. This finding is identical to those of non-triggered specimens in terms of number of laminates and length, but the amount of absorbed energy in triggered specimens exceed that in the non-triggered specimens. The maximum obtained value for CFE in the specimen with 30 layers of ramie bio-epoxy® laminates and 50 mm length was equal to 0.54. This value is 1.7 times greater than that achieved in non-triggered specimens. Thus, geometries and trigger play significant functions in the energy absorption capacity and failure mode of composite tubes; in other words, thicker, shorter, and triggered composites are able to absorb more energy. Morphological analysis of tubes after failure showed that high-friction sliding of the tube against metal plates and trigger, delamination, and tear at the corners and at the tube and trigger intersection are the main mechanisms that contributed to energy absorption. The findings might be used as the basis of design guidelines for the use of ramie in crashworthy systems and safety applications.,Ph.D.
Pages:	161
Call Number:	TL242.J334 2019 3 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

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