To investigate the high-velocity impact response and damage evolution of the triaxial braided composite fan case, a series of ballistic impact tests using blade-like projectiles were conducted. Cylindrical projectiles of the same cross-section perimeter were also employed to identify the influence of projectile geometry. In addition, satin woven composites were tested for comparison with respect to failure modes and damage shape. Experimental results indicate that the main failure modes for the two different fiber reinforcement architectures are similar, that is, fiber shear failure and matrix crush failure in the impact surface and fiber tensile failure, fiber pull-out, matrix cracking, and delamination in the exit surface. The damage area in the exit surface is diamond-shaped for satin woven composites while rounded or elliptic for triaxial braided composites according to projectile geometry. The triaxial braided composites have an improved ballistic resistance and higher ballistic limit than satin woven composites. Based on damage area and failure modes observed from experiments, ballistic behavior was predicted using an analytical model, which proves to be accurate enough.

The application of abradable seal coating is an effective method to improve the efficiency of turbine engines. The AlSi-polyester is a typical one, which has been widely used in mediate and low pressure compressors. To evaluate abradable performance and investigate wear mechanisms of these seal coatings, a high-temperature and high-velocity tester was constructed, with 520 m/s maximum blade tip speed and 5–2000 μm/s incursion speed and 1200℃ maximum heating temperature. Abrasion tests with blade tip velocities between 150 and 300 m/s and incursion rates between 13 and 500 μm/s have been conducted under 350℃ to investigate the wear behavior between Ti6Al4V blade and an AlSi-polyester coating sample. The coating abradability was evaluated after abrasion tests through analyzing the mass losses, wear morphology, and interaction force of the coating and blade. It is found that the AlSi-polyester seal coating used in our research has good abradability to protect the Ti6Al4V blade tip, and abrasion wear is its predominant wear mechanism with furrow surface morphology. Incursion per pass has significant impact on the variation tendency of interaction force, with tests at low incursion per pass showing stable tendency and lower force, whereas tests at high incursion per pass showing gradual rise before relatively stable trend and higher force. This work provides a new basic data for the preliminary study of the interaction between blade tips and abradable coatings in aero-engine applications.

An experimental and numerical investigation on the aeroengine blade/case containment analysis is presented. Blade out containment capability analysis is an essential step in the new aeroengine design, but containment tests are time-consuming and incur significant costs; thus, developing a short-period and low-cost numerical method is warranted. Using explicit nonlinear dynamic finite element analysis software, the present study numerically investigated the high-speed impact process for simulated blade containment tests which were carried out on high-speed spin testing facility. A number of simulations were conducted using finite element models with different mesh sizes and different values of both the contact penalty factor and the friction coefficient. Detailed comparisons between the experimental and numerical results reveal that the mesh size and the friction coefficient have a considerable impact on the results produced. It is shown that a finer mesh will predict lower containment capability of the case, which is closer to the test data. A larger value of the friction coefficient also predicts lower containment capability. However, the contact penalty factor has little effect on the simulation results if it is large enough to avoid false penetration.

In this study, the effects of residual stress induced by three different cooling methods during heat treatment on the crack propagation behaviour of the GH4169 disc were investigated. Different levels of stress fields were induced to the specially designed discs by using air cooling (AC), air jetting cooling (AJC) and water quenching (WQ) methods and were quantitated by numerical simulation. These discs were then subjected to prefabricated cracking, and crack propagation tests were conducted on a spin tester with two load spectrums. Crack growth behaviour was depicted via the surface replica technique and fracture morphology. Regarding the linear superposition of residual stress and centrifugal force, the crack propagation behaviour of different discs was simulated using the FRANC3D software. AJC and WQ introduced compressive residual stress (−259 MPa and −109 MPa, respectively) into the disc compared with the AC method (about −1.5 MPa). The AJC method increases the crack propagation life of the disc by introducing residual compressive stress into the area near the surface of the central hole to inhibit the opening of the crack surface. When the fatigue load was low, this inhibition effect was more significant.

A series of ballistic tests on triaxial braided carbon/epoxy composites were described in Part I of this paper. In this part, numerical simulations were carried out to investigate the impact response, damage evolution, and penetration mechanisms of these composites. A continuum finite element model was developed to obtain the time history of the projectile velocity, displacement, penetration resistance force, and energy absorption during the impact process. By fitting the numerical data, the ballistic limit velocity can be obtained. Good agreements were achieved between numerical results and experimental results. Numerical predictions for ballistic tests of the composites indicate that, based on variations of damage mechanisms and failure features, the impact process can be subdivided into three stages, i.e. phase I – shock compression, phase II – bulge deformation, and phase III – penetration process, among which phase II consumes most of the projectile kinetic energy. The differences between a blade-like projectile and a cylindrical projectile in the impact process are also addressed in detail.