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Yang Y.,Northwestern Polytechnical University | Sun X.,Northwestern Polytechnical University | Sun X.,China Aircraft Strength Research Institute | Yang S.,China Aircraft Strength Research Institute | And 2 more authors.
Fuhe Cailiao Xuebao/Acta Materiae Compositae Sinica | Year: 2012

The compressive failure mechanism of low-velocity-impacted composite laminates was studied by means of delamination configuration obtained by ultrasonic C-scan, strain field by strain gauges, and damage process by acoustic emission. The results show that serious stress concentration appears leading to subsequent fiber breakage and triggering catastrophic failure of the laminate because of unsymmetrical delamination distribution within the laminate. The key factor in compressive failure mechanism of impacted composite laminates was fiber breakage rather than delamination propagation.


Yang Y.,Northwestern Polytechnical University | Chai Y.,China Aircraft Strength Research Institute | Chi J.,China Aircraft Strength Research Institute | Chen X.,China Aircraft Strength Research Institute | Lin G.,China Aircraft Strength Research Institute
Fuhe Cailiao Xuebao/Acta Materiae Compositae Sinica | Year: 2011

The effects of fiber angel orientation and mixed-mode ratio of interlaminar fracture on the properties of delamination were experimentally studied in the laminate propogates. The results show that 0° ply is able to stop delaminating from jumping into adjacent plies in mode I interlaminar fracture; fracture toughness of unidirectional laminate at all mixed-mode ratios could be regarded as the conservative value; the curve of mixed-mode fracture toughness resembles sine as the mixed-mode ratio varies.


Liu X.,Northwestern Polytechnical University | Guo J.,China Aircraft Strength Research Institute | Sun X.,Northwestern Polytechnical University | Sun X.,China Aircraft Strength Research Institute | Mu R.,China Aircraft Strength Research Institute
Hangkong Xuebao/Acta Aeronautica et Astronautica Sinica | Year: 2013

A full-scale civil airplane fuselage section with 7 frames is designed and manufactured whose cabin section is configured with three rows of seats and two overhead bins. A finite element model of the fuselage section and cabin Interiors is developed, and a 7 m/s vertical impact condition is confirmed by two pretest analyses. The impact surface is a wooden platform instrumented with 12 load cells. The passengers are simulated by 15 dummies, of whom four are instrumented, and the passenger baggage is simulated by concentrated weights. The impact loads and acceleration responses of the structure and dummies are collected by a data acquisition systems (DAS) which is synchronized to high speed cameras. Experimental data processing methods are introduced and typical experimental curves are presented. The energy absorption process and mechanisms of the fuselage section during the impact are estimated, and three general methods of improving the fuselage structural crashworthiness are proposed. Based on the structural requirements and human injury criteria of the transport airplane airworthiness regulation, a crashworthiness evaluation method called the integrated crashworthiness index (ICI) is introduced, which can score the crashworthiness with a standard formula. The crashworthiness of the fuselage section structure is evaluated with ICI. The evaluation result show that the fuselage section structure meet the crashworthiness requirements well under the given impact environment.


Zhang H.,China Aircraft Strength Research Institute | Wu J.,China Aircraft Strength Research Institute
Procedia Engineering | Year: 2015

Nonlinearitiesin designing aircraft are inevitable. It is necessary to investigate the effects of them on the dynamic response. The aeroelastic dynamic model with freeplay nonlinearity in pitch degree of freedom is established with the Theodorsenaerodynamic model. The harmonic balancemethod is employed to obtain the flutter boundary. Then the nonlinear responses and the stability characteristic are studied by using the time marching aeroelastic method. The effects of the initial displacement in pitch degree of freedom and the gap size on the LCO characteristics are investigated. Results show that the appearance of the LCO depends on the initial condition and the flow speed. The velocity range for the existence of the LCO and the LCO amplitude are related to the freeplay gap. © 2015 The Authors.

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