Papers by Author: Bin Jun Fei

Abstract: Low velocity impact tests were carried out on T300/QY8911 and CCF300/QY8911 composite laminates, which led to similar impacted damage characterized by dent depths on laminates. Compression/compression fatigue strength tests of the impacted laminates were further conducted. The comparison of the compression/compression fatigue performance between the two types of composite laminates with similar impacted damage shows the compression/compression fatigue behaviors of T300/QY8911 and CCF300/QY8911 are similar. It follows that the CCF300/QY8911 is an effectively alternative to the T300/QY8911 in damage tolerance behavior.

Abstract: Damage resistance behaviors of CCF300/5428 laminates under five levels of impact energies have been researched by using progressive damage method. The progressive damage models (PDM) are composed of 3D finite element models, Hashin-type failure criteria and Camanhos degradation rules. The impact procedure has been simulated by the progressive damage analysis with user defined subroutines which have been developed and embedded into the general finite element analysis package. The history curves of the contact force and the impact point displacement are plotted. The global damage at typical events for various impact energies is investigated.

Abstract: In order to research the static properties of FRP composite laminates with central hole, the numerical simulation and experimental method are used. The simulation is achieved by the finite element analysis tool with the progressive damage method. During the simulation, the Hashion failure criteria and the selective completed material degradation models are adopted. Proper specimens of FRP composite laminates with central hole are prepared and the static tests are carried out. The results indicate that progressive damage method can simulate the failure process of FRP laminates with central hole and the simulative results agree well with the experimental data.

Abstract: Progressive damage method is adopted to predict the static mechanics properties of FRP composite laminates with central hole. Progressive damage models with three different 3D failure criteria and material degradation models are established and analyzed via a user defined subroutine embedded into the general FEA package. Numerical results indicate that all the three 3D failure criteria can simulate the failure process of FRP laminates with central hole, but the final failure load is different. Degradation coefficient and the finite element mesh have significant effect on the numerical results.

Abstract: The effects of humidity and ultraviolet radiation aging on fatigue properties of carbon/ bismaleimide composites and coating protection action were presented. Specimens with central hole are made of carbon/bismaleimide laminates. Compression-compression (C-C) fatigue tests under normal lab environment were operated respectively for four groups of specimen, (1) specimen under normal lab environment, (2) specimen under UV radiation aging with dryness, (3) specimen under UV radiation aging with moisture, and (4) specimen with coating under UV radiation aging with moisture. Variance analysis of experimental outcomes gave significances of the environment effects on C-C fatigue life of specimens. The results reveal that UV radiation have remarkable effects on the C-C fatigue life of the composite laminates under the same humidity, whereas combined action of UV radiation (300MJ/ m2) and humidity have no significant effects on the C-C fatigue life. Coating can provide effective protect the specimen from UV radiation aging.

Abstract: A progressive damage method is adopted to predict the structural strength of a woven out-of plane composite bonded π joint. A 3D progressive damage model is established and analyzed via a user defined subroutine embedded into the general FEA package. The numerical prediction gives the information of damage onset, damage propagation and final failure pattern, initial and final failure strength. Three samples of woven composite π joint under tensile load are tested to verify the numerical results. The numerical prediction agrees well with the experimental outcomes. All the numerical and experimental results provide insight into the basic understanding of static strength of woven composite bonded π joint.

Abstract: TBCs is a type of multilayer systems, mainly used in the thermal parts of aero engine, acting as the part of heat insulation. The using temperature of parts can be improved because of the being of TBCs. TBCs is one of the most advanced high temperature coatings, and it has many perfectly properties, including the chemical property at high temperature, anti-erode and thermal insulation [1,2]. If TBCs spall from the base, the base will expose in the high temperature, then, rapidly destroy. TBCs generally include three layers, superalloy, bonding layer, insulation layer, and the thermally grown oxide (TGO) between the bonding layer and insulation layer. Justly because of the being of TGO, the TBCs easily failed [3,4]. Although many researchers studied the oxidation of TBCs, the investigation of the relations between oxidation and oxide temperature has not been done by far. So, the work put the emphases on the discussion of APS TBCs’ oxidation property in different temperatures by experiment.

Abstract: A finite element simulation of a plasma sprayed thermal barrier coating(TBC) system was conducted. Plasma sprayed thermal barrier ceramic coating was treated as either a simple elastic model or an advanced viscoplastic model which includes rate dependence and unequal flow stresses in tension and compression. Predicted tensile stresses emerging in the ceramic plane at the elevated temperature never become large enough to cause surface cracks based on elastic analysis, so does using the viscoplastic model. At the low temperature, these two models identically show that the ceramic coat will locally cracks at the “peak” location. It is shown that although there are some numerical differences in these two models’ predictions, elastic analysis predicts accurate in failure mechanism analysis based on stresses

Abstract: As more aircrafts reach or exceed their design life, it is becoming very important to research multiple cracks damage, especially the multiple site damage (MSD) in order to re-evaluate their service life and damage tolerance/durability performance. The existing of MSD may remarkably reduce the residual strength of an aerospace structural component than those with a singe lead crack. This study investigated the residual strength of aluminum alloy sheet with MSD through three types of aluminum specimens test. Aluminum panels with bare collinear constant diameter holes were chosen as specimens. After some constant amplitude tension-tension load cycles, the MSD were found in these specimens since there were multiple fatigue cracks emanating from the saw cuts of holes. The residual strength was recorded as the maximum load when every specimen was subjected to monotonically increasing tensile load until failure occurred. In different failure prediction criteria that were often used in engineering in order to evaluate the accuracy of these criteria, Swift criterion (ligament yield) criterion got more accurate prediction results than other criteria. Although Swift criterion was more accurate than some other criteria, its error was still big for some specimens. Two modified approaches were proposed in order to get more accurate and appropriate failure criterion for MSD structure.

Abstract: Studies about the effect of stress characteristics on multi-axial high-cycle fatigue of metals are still insufficient. Up to now, little work about the effect of different ratio of stress amplitude has been done on multi-axial fatigue under the same equivalent stress. In this paper, the effect of ratio of stress amplitude, under the same Von-Mises equivalent stress is studied from theory and experiment. The results show that the main factor of multi-axial high-cycle fatigue failure is the maximum principal stress. For proportional loading, fatigue life raises when ratio of stress amplitude increase. The variety of fatigue life is not obvious when is larger than a certain value and its value closes to that of pure torsion. For non-proportional loading, when ratio of stress amplitude increases, fatigue life raise at first, then has an inflection point. The value of at the inflection point changes with phase difference and its value is 0.5 while phase angle is 90º. Fatigue life of uniaxial tension was lower than that of pure torsion.