Energy Absorption Characteristics Of Radially Corrugated Composite Shells Under Different Quasi-Static Loading Conditions
Abdewi, Elfetori Faraj (2007) Energy Absorption Characteristics Of Radially Corrugated Composite Shells Under Different Quasi-Static Loading Conditions. Masters thesis, Universiti Putra Malaysia.
This research is devoted to investigate the effect of structural geometry on the crushing behaviour, energy absorption, failure mechanism, and failure mode of radially corrugated composite shells. A multi-discipline literature review on the use of composite materials in the field of crashworthiness was carried out. Based on the literature review findings, new composite structure (Radially Corrugated Composite Tube RCCT) was proposed to be fabricated and investigated experimentally. An extensive experimental program has been performed through four main phases. First phase involves fabrication and testing of three different sizes of cylindrical composite shells. Three sizes of Cylindrical Composite Tubes (CCT) were first tested mainly in order to set the basis for comparison when testing subsequent radially corrugated tubes. Moreover, to find out the effect of tubes’ diameter to thickness ratio (d/t) on energy absorption capability. Second phase deals with comparison between three geometrical different shells: Cylindrical Composite Tube (CCT), Radially Corrugated Composite Tube (RCCT), and Combined Radially Corrugated Composite Tube (CRCT). Results found at this phase shows that RCCT fit to proceed for further investigation. The comparison between tested models at each phase has been carried out based on the criteria of maximum energy absorption. The third phase involves examining the corrugation profile. Three different profiles have been examined (Sinusoidal Profile Corrugated Tube (SPCT), Triangular Profile Corrugated Composite Tube (TRCT), and Trapezoidal Profile Corrugated Composite Tube (TZCT)). Results found show that radially corrugated tube with sinusoidal profile gives the best result in terms of energy absorption capability. Finally, further investigations have been carried out on the tube with sinusoidal profile in order to test the effect of corrugation density. At this phase, in addition to the 16-corrugation that have been tested, three more models with same dimensions and different corrugation densities had also been tested. 18-corrugation, 20-corrugation, and 22-corrugation (RCCT-18, RCCT-20, and RCCT-22) have been investigated. Here, it is wise to mention that all corrugations have the same shape and dimensions. Moreover, 22 corrugations were found the maximum number of corrugations that can be fabricated in the tube circumference. In other words it was impossible to fabricate a tube with more than 22-corrugations at that certain diameter, since all tested composite tubes have the same length and diameter at all testing phases. Results show that corrugation density has an influence on the performance of composite shells as an energy absorber. It has been found that as corrugation density increases, total energy absorption increases. All models were subjected to two kinds of load: axial as well as lateral quasi-static compressive load. Transfer from one phase to another was carried out based on the results of axial load. All models were tested under same condition. For axial tests,RCCT exhibits excellent results compared to other models through out all research phases. However, for lateral tests, there is a little influence of the geometry on the tested parameters. Failure modes were examined for each specimen using digitally recorded photographs taken during the crushing of the specimens and employing optical microscope. Linear buckling finite element was conducted for all models using commercially available Finite Element Software (LUSAS). Numerical results presented via includes predicted critical load, deformation mesh, and stress contours. Experimental and numerical results were presented for all models at different load cases. Results obtained show good agreement between experimental and numerical study. Among all models, radially corrugated composite tube with sinusoidal profile and 22-corrugation density model (RCCT-22) exhibit the best result with respect to the tested parameters.
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