Jialing Yang

Experimental study on crushing characteristics of brittle fibre/epoxy hybrid composite tubes

The collapse characteristics and energy-absorption capability of three kinds of hybrid composite tubes, G827-G803/3234, G827-G803/5224 and G827-759/5224, are studied in the present article. Each of the specimens containing two kinds of brittle fibre has been examined by both axial quasi-static and impact crushing test. The effects of fibre type, fibre content and loading conditions on the crushing-failure characteristics, peak load and energy-absorption capability are discussed. The test results show that for G827-G803/3234 tubes, the crushing failure mode is changed from the splaying mode to the fragmentation mode when quasi-static loading is changed to impact loading, while for others there is no such characteristic. The fibre type and fibre content have significant influences on peak load. It is observed that the tubes containing only one kind of brittle fibre have lower peak load than the ones containing two kinds of fibres with approximately equal hybridisation contents. The energy-absorption capability can be improved by reasonably hybridising with two kinds of brittle fibres. Generally, the energy-absorption capability is reduced remarkably under impact crushing test in comparison with that under quasi-static test.

Theoretical analysis and multi-objective optimisation for gradient engineering material arresting system

ABSTRACT Aircrafts may overrun the runway during take-off and landing, leading to a catastrophe involving aircraft damage and even loss of life. In order to protect aircrafts and crews from casualty, a gradient engineering material arresting system (GEMAS) was developed to arrest the overrun aircrafts with different size in comparatively short distances securely. This paper presented an analytical model to predict the crushing resistance exerted on the aircraft landing gear, and the corresponding numerical model was established to validate the accuracy of the analytical results. Response surface model for design of experiment (DOE) as well as numerical simulations was employed to conduct multi-objective optimisation to seek for the optimal design parameters for GEMAS. Besides, parametric investigations were performed to discuss the effects of initial height, dipping angle and material strength on the design response (drag ratio and penetration depth) for the GEMAS according to the DOE results. Finally, multi-objective optimisation design was engaged in improving the arresting system by means of a desirability approach, aiming at obtaining the specific drag ratio and the minimum penetration simultaneously.

Improving safety of runway overrun through foamed concrete aircraft arresting system: an experimental study

Aircraft may overrun the ends of runways, sometimes with disastrous consequences. Because of the capability of high energy absorption, a foamed concrete arresting system can be employed to safely decelerate and stop the overrunning aircraft. In order to evaluate the performance of the foamed concrete arrestor system, a full-scale arresting test with an instrumented Boeing 737-300 aircraft has been conducted. The test bed of 140 m long by 15 m wide and 0.32 m deep was constructed to demonstrate the effectiveness of safely stopping the Boeing 737 aircraft entering the bed at 40 knots. In the test, the deceleration experienced by the aircraft was recorded in addition to its instantaneous speed, dynamic responses of the landing gear, and rut depths. Then, the validity of the analytical prediction model developed in previous study was examined by means of the full-scale test data. The results of the full-scale test show that the foamed concrete arrestor could provide an effective deceleration without exceeding the design allowable stresses on the landing gear during arrest process. Using the analytical model, the sensitivity of aircraft stopping distance was evaluated as a function of arrestor material compressive strength, aircraft weight, and arrestor-bed thickness. Based on these investigations, it is recommended that the foamed concrete system can be used as an alternative civil aircraft arresting system to improve the runway safety.

Dynamic plastic behavior of a free–free beam striking the mid-span of a clamped beam with shear and membrane effects considered

Abstract Recently Yu et al. (Int. J. Solids Struct. 38 (2001) 261) made a study on the dynamic behavior of a flying free–free beam striking the tip of a cantilever beam using the rigid, perfectly plastic (r-p-p) material model. Later, also based on the r-p-p material model Yang and Yu (Mech. Struct. Mach. 29 (2001) 391) analyzed another impact problem of a free rotating hinge beam striking a cantilever beam. Both of these studies ignored the finite deflection effects on the plastic behavior of the colliding beams. However if the free–free beam strikes a clamped beam, the influence of finite-deflections, or, geometric changes, must be retained in the governing equation if the maximum permanent transverse displacement of the clamped beam exceeds the corresponding beam thickness. The problem becomes more interesting since the deformation mechanisms of the beam system and the partitioning of energy dissipation in the beams are significantly different from those predicted by ignoring the influence of membrane forces. Accordingly the failure modes of the structure are different. In the present paper, a theoretical model based on the r-p-p material idealization is proposed to simulate the dynamic behavior when the mid-point of a translating free–free beam impinging on the mid-span of a clamped beam with the beam axes perpendicular to each other. The plastic behavior of the beam system is explored with shear sliding and finite deflection effects taken into account. The final deflection, the dissipation of energy within the two beams after impact and the influence of the structural and material parameters are discussed. It is shown that membrane force plays an important role during the response process, especially when the deflection is of the same order as the thickness of the clamped beam.

Fluid–structure interaction analysis of the drop impact test for helicopter fuel tank

Abstract The crashworthiness of helicopter fuel tank is vital to the survivability of the passengers and structures. In order to understand and improve the crashworthiness of the soft fuel tank of helicopter during the crash, this paper investigated the dynamic behavior of the nylon woven fabric composite fuel tank striking on the ground. A fluid–structure interaction finite element model of the fuel tank based on the arbitrary Lagrangian–Eulerian method was constructed to elucidate the dynamic failure behavior. The drop impact tests were conducted to validate the accuracy of the numerical simulation. Good agreement was achieved between the experimental and numerical results of the impact force with the ground. The influences of the impact velocity, the impact angle, the thickness of the fuel tank wall and the volume fraction of water on the dynamic responses of the dropped fuel tank were studied. The results indicated that the corner of the fuel tank is the most vulnerable location during the impact with ground.

An Exact Analytical Solution for Thermoelastic Response of Clamped Beams Subjected to a Movable Laser Pulse

The thermoelastic dynamic response of a clamped Bernoulli beam was studied when it was irradiated by a movable, temporally non-Gaussian, laser pulse. Both the energy absorption depth and the time decaying effects were considered. The temperature distribution, deflection, vibration acceleration, and stress of the beam were derived analytically, and the variations of them with time and space were illustrated. It was shown that the vibration frequency is independent of the scanning speed of the laser pulse. It is important to notice that, although the deflection of the beam is small, high vibration acceleration can be induced in microbeams, which is important for failure and fracture of the beam. Moreover, compressive stress is induced in the beam, but the importance of temperature-induced stress and deformation-induced stress may be different according to the duration time and moving speed of the laser pulse.