Papers by Author: Dong Ruan

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Authors: Rafea Dakhil Hussein, Dong Ruan, Jeong Whan Yoon
Abstract: Thin-walled honeycombs have been extensively investigated and they are often used as sandwich panels to enhance the energy absorption in many applications including vehicles. In this study, axial compressive tests at three different velocities (3, 30 and 300 mm/min, respectively) by using an MTS machine were conducted with both empty and hybrid aluminium tubes filled with aluminium honeycomb. The aim of this work is to study the contribution of aluminium honeycomb in square hybrid tubes in terms of the deformation mode and energy absorption. Square aluminium tubes made of AA 6060-T5 with two different side lengths, 40 and 50 mm, were used. Two types of honeycombs made of AA 5052 with different cell wall thicknesses were used in this study. The force and displacement of the tubes were recorded during the test. The specific energy absorption (SEA) of honeycomb-filled tubes was compared with the sum of the SEA of an empty tube and honeycomb. It was noticed that the SEA of the hybrid tubes depended on the honeycomb density and the loading velocity within the velocity range studied.
Authors: Dong Ruan, Mohd Azman Yahaya, James Hicks, Jayson Lloyd, Feng Zhu
Abstract: Sandwich panels consisting of two aluminium two face-sheets and a core made of aluminium honeycomb were studied in this paper. These sandwich panels are good candidates for cladding systems employed to protect other structures again blast loadings. In this paper, the mechanical response and deformation of these sandwich panels subjected to simulated blast loadings are investigated experimentally. The effects of impact pulse, foil thickness and cell size of aluminium honeycombs have been discussed.
Authors: Asm Ashab, Dong Ruan, Guo Xing Lu, Yat C. Wong
Abstract: Aluminum honeycombs are lightweight and have good energy absorption capability. They are widely used in industrial products and also as core materials in various fields of engineering such as aerospace, automotive and naval engineering because of their high specific strengths and they can undergo large plastic deformation to absorb high impact energy. In the applications of aluminum honeycombs they are not only subjected to pure compressive or indentation load but sometime also under combined compression-shear load. The mechanical response and crushing behavior under combined compression-shear loading condition is still limited in literature. In this paper, quasi-static out-of-plane combined compression-shear tests were conducted to study the deformation mechanism of different types of HEXCELL® aluminum honeycombs with different cell sizes and wall thicknesses. Three types of aluminum honeycombs were used in this study. A universal MTS machine with specially designed fixtures was employed in the quasi-static loading tests. The experiments were conducted at three different loading angles, that is, 30°, 45° and 60° and in TL and TW (T is out-of-plane direction and L, W are the two in-plane directions) plane orientation loading directions of aluminum honeycomb. The effects of different loading angle and different plane orientation are reported in this experimental study. Similarly, the effects of cell size and cell wall thickness were also analyzed.
Authors: Rafea Dakhil Hussein, Dong Ruan, Guo Xing Lu
Abstract: In this study, hollow square carbon fibre reinforced plastic (CFRP) tubes and aluminium sheet wrapped CFRP tubes have been axially crushed at a quasi-static loading velocity of 0.05 mm/s. A specially designed and manufactured platen with four cutting blades was used to cut and crush these two tubular structures. The four cutting blades had height of 5 mm and width of 3 mm with round tip to reduce the initial peak force and achieve a stable crushing deformation mode. Notches at one end of each tube were utilized to control the location of initial failure. The crashworthiness characteristics of hollow CFRP tubes and aluminium sheet wrapped CFRP tubes with notches that crushed by the platen with cutting blades were compared with those of tubes that crushed by a flat platen. Experimental results showed that using the platen with blades to crush the specimens with notches exhibited more stable deformation mode than the specimens without notches. Mean crushing force, energy absorption and specific energy absorption (SEA) increased when CFRP was wrapped with aluminium sheet and crushed by the platen with blades. The increase of average value of mean crushing force, energy absorption and specific energy absorption of aluminium sheet wrapped CFRP tube and crushed by the platen with blades are 16.5%, 17.3% and 5% respectively more than those for hollow tubes that crushed by a flat platen.
Authors: Feng Zhu, Bin Hui Jiang, King H. Yang, Dong Ruan, Mike S. Boczek, Rabih Tannous
Abstract: SKYDEX material is an advanced lightweight porous medium consisting of layers of periodic twin-hemispherical microstructures made of thermoplastic polyurethane. This material is used widely in personnel and structural protection. This paper reports a combined experimental and numerical study on crushing behavior of such material. Compression tests were conducted on the SKYDEX panels at the strain rates of 0.01~10 s-1. A 3D finite element model was developed and validated against experimental data. Based on the FE model, the deformation mode of the microstructures, strength, energy absorption, as well as strain rate effect were predicted and analyzed. Additional simulations were conducted to establish the relationship between the peak strength coefficient and relative density. SKYDEX® material has been found to be a competitive energy absorber among cellular solids.
Authors: Rafea Dakhil Hussein, Dong Ruan, Guo Xing Lu, Akshay Kumar
Abstract: The aim of this study is to find the best platen with blades as a new energy dissipating mechanism that causes considerably damage to CFRP/aluminium tubes. Specially designed and manufactured platens with five different cutting blade profiles were used to simultaneously cut and crush square CFRP tubes and aluminium sheet-wrapped CFRP tubes. The platens with blades were evaluated in terms of the deformation mode, mean crushing force, energy absorption and specific energy absorption of tubes. Experimental results showed that tubes cut and crushed by the platen with 45o inclined blades had the best crushing performance and exhibited a more stable deformation mode compared with those for tubes cut and crushed by other platens with different blade profiles. The platens with blades acted as trigger mechanisms that minimise the initial peak crushing force and maximise the energy absorption of tubes compared with tubes crushed by flat loading platens.
Authors: Martin Vcelka, Yvonne Durandet, Christopher C. Berndt, Dong Ruan
Abstract: Experimental observations and data are employed to elucidate the effect of indenter size on the deformation and energy absorption of composite sandwich beams. Unlike metal face sheets that yield and plastically deform to create an intact indentation zone; composite face sheets tend to fail in a brittle manner resulting in fibre breakage that leads to widespread fracture. This mode of failure can dictate how the load is transferred throughout the structure and directly affect the energy absorption character of the composite sandwich beam. Quasi-static and low velocity impact (LVI) three-point bending experiments with various indenter diameters were conducted to observe the interaction between indenter and face sheet and the energy absorption properties. The results are compared with existing analytical expressions.
Authors: Shan Qing Xu, Dong Ruan, Jason Miller, Igor Sbarski, Ajay Kapoor
Abstract: In this paper, the uniaxial dynamic compressive response and rheological properties of a newly developed commercially available polymer based shear stiffening (PSS) composite is experimentally studied at different crushing velocities. The results showed that the compressive stress of PSS composites increases with the rising strain rates. Comparing the stress-strain curves of PSS composites and neoprene at the same strain rate, it was found that the compressive stress of PSS composite increased gradually with strain, while the compressive stress of neoprene increased sharply with strain. The uniaxial dynamic mechanical analyses of PSS composites showed that storage modulus of PSS composite increased with the increase of sweep frequency. The rheological study of PSS composites showed that the storage modulus of PSS composite significantly increased when the angular frequency was higher than a critical value, e.g., 100 rad/s, demonstrating evident shear stiffening properties.
Authors: Shan Qing Xu, Dong Ruan, John H. Beynon, Guo Xing Lu
Abstract: The compressive behavior of two closed cell aluminum foams (Alporas and Cymat) were investigated under various strain rates from 10-3 to 102 s-1 using compressive tests conducted on MTS and Instron test machines. High speed camera videos show that localized deformation occurs in Alporas foam specimens uniformly, but not in Cymat foams. The stress-strain curves for Alporas foams are smooth and regular, while they oscillate dramatically for Cymat foams. Alporas foams exhibit strain rate sensitivity, i.e. with an increase in strain rate, the normalized plateau stress and energy absorption capacity increase. The plateau stress for Cymat foams was more sensitive than Alporas to strain rate, but the energy absorption less so, at least at a nominal relative density of 10%.
Authors: Mohd Azman Yahaya, Dong Ruan, Guo Xing Lu
Abstract: Similar blast loading characteristics can be obtained using impact of aluminium foam projectiles, which enables blast tests to be mimicked in a laboratory scale and in a safer environment. The purpose of this study is to determine the back-face deflection history of aluminium sandwich panels experimentally by aids of a laser displacement meter when panels are subjected to the impact of metal foam projectiles. This information was usually determined using finite element analysis (FEA) due to the difficulty in the experiment. The projectiles are cylindrical ALPORAS aluminium foam with diameter of 37 mm, length of 50 mm and nominal relative density of 10%. The sandwich panels consist of two 1 mm aluminium face-sheets and an aluminium honeycomb as the core. There are five different core configurations with a brand name of HEXCEL. The projectiles are fired towards the centre of the sandwich panels at different velocities using a gas gun. During the tests, a laser optical displacement measuring device is used to record the history of the back-face deflection experimentally. The deflection of the back-face is found to reach the maximum before coming to rest at a smaller value. The final back-face deflections of the sandwich panels show exponential relationship with the projectile impulse. The final deflections are compared with the deflection of monolithic plates with equal mass. The sandwich panels deflect less than the monolithic plate with an equal mass up to a critical value but continue to increase significantly afterwards. Care should be taken when using sandwich panels as protective structures against foam projectiles as beyond this point, the monolithic plates outperform the sandwich panels in absorbing the impact load.
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