Li Bin Zhao

Experiment Research of Environment Effects on Fatigue Life of Carbon/Bismaleimide Composite Laminates with Central Hole

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.

Tensile Strength Prediction of Woven Composite Bonded Joint

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.

Crack Growth Life Estimating for MSD Panel

The problem of multiple site damage (MSD) has got more attention in ageing structures. Cumulative effects of interacting cracks may significantly degrade the damage tolerance capacity of structures. Cracks caused by MSD are extremely difficult to detect and greatly reduce the residual strength, fatigue life and overall structural integrity of aircraft panels. This paper presents a simple numerical method, which use the principles of fracture mechanics and the computation results, to predict the fatigue crack growth life of MSD structure. Comparing with calculating crack growth life cycle by cycle, this method will save much time. To verify the validity of the proposed method, experiment was conducted and reported with simulation specimen of representative MSD structure with 5 details. The comparison between the calculated a-N curves and the crack growth lives and the test results shows that the prediction result with this fast method is acceptable. A discussion was carried out by numerical analysis; in with typical MSD structures with different initial crack length were adopted. Crack interaction effect was found obviously, but it occurred mainly in the last part of the crack growth lives. The relative size of MSD cracks depends significantly on the distribution of the initial cracks.

Mechanics Design of Connecting Frame in Aircraft Composite Cabin

The mechanics behaviour of connecting frame in aircraft composite cabin under static load can be expatiated through its dangerous key components. Initial damage and ultimate strength of the key component are studied using progressive damage method. Based on the strength prediction technique, the effects of composites ply angle and the structural layout on structural initial damage and ultimate failure are discussed to exploit the potential composite structural load carry ability. The numerical results show the ply angle modification can provide 26.3% increase on initial failure stress and 14.1% on ultimate strength. Farther structural layout adjustment can significantly increase the ultimate strength whereas go against the initial failure strength. The design scheme with concave boxes to cope with assembly demands is verified to be practical in joint structures by comparing with a connecting frame without concave boxes.

Taylor Series Numerical Method in Structural Dynamics

Taylor series numerical method is a novel time integration method for structural dynamics. In comparison with the well-known ones, Taylor series method has high accuracy and good convergence characteristics and thus is a good alternative for solving structural dynamics problems. In the paper, the recursive formulae of Taylor series numerical method in linear and nonlinear structural dynamics are derived. The desired user routine in Fortran 90, which was compiled and linked into the general software ANSYS program, is designed and programmed. User-defined menus are constructed via the User Interface Design Parameter. Numerical examples illustrated the validity of the customized plug-in. The research in this paper promotes the algorithm application in complicated engineering problems.

Failure Analysis of Single-Lap Single-Bolt Composite Joints with Countersunk Fasteners

A failure analysis of a single-lap single-bolt composite joint with a countersunk fastener was carried out using a progressive damage model. The FE model considering the distributions of fine and coarse meshes, appropriate contact pairs and the bolt preload was established. Based on the analysis, the five stages in the load-displacement curve and the changes of tilt angle were discussed in detail as well as failure contours of hole laminates at typical events during the damage propagation are illustrated. The inherent development tendency of the tilt angle accompanying with the damage propagation in the single-lap joint vividly depict its failure process.

Taylor Series Numerical Method in Transient Heat Conduction Analysis

Taylor series numerical method (TSNM) is extended to the field of transient heat conduction. Theoretical description of TSNM for transient heat conduction problems is presented. Furthermore, the algorithm is realized and embedded in commercial software ANSYS®. If a lumped mass heat capacity matrix provided, the governing equation of transient heat conduction problems, which is a differential equation, will be solved by a series of recursion calculation of Taylor expanding coefficients. A typical transient heat conduction problem with analytical solution was discussed to verify the TSNM. At last, the TSNM is applied in the transient heat analysis of an all-solid fiber optic gyro (FOG).

Fatigue Stiffness Degradation Behaviour of Woven Composite π Joint

Fatigue stiffness degradation behaviour of woven composite π joint subjected to tensile-tensile cycle loading is studied. Because of the complex structural configuration of woven composite π joints and a variety of failure modes, there exhibited four stiffness degradation modes in fatigue test. For example, stable slight reduction mode, abruptly decreasing mode, step decreasing mode and constant stiffness mode. Each stiffness degradation mode has a corresponding failure mode in fatigue test.

Damage Resistance Behaviors of CCF300/5428 under Various Impact Energies

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.

Deformation Analysis of Beam Pipe Installation Mechanism for EPC

Beam pipe is a key part of the electron positron collider (EPC). It is very expensive and hard to install due to a limited room and high assembly precision requirement. In order to ensure the beam pipe being installed successfully, an installation scheme is introduced. Key factors affected the deformation of installation mechanism are presented by classical mechanics theory. Different finite element models were analyzed to obtain an optimal geometry size for the protective shaft based on commercial software ANSYS®. The deformation of the determinate installation mechanism satisfies the engineering requirement well.