Bird and hail stone impact resistance analysis on a jet engine composite air inlet

Abstract

Abstract. Bird or hail stone impacts are an important phenomenon that must be taken into consideration when designing aircraft. As engines are the sole thrust-providing mechanisms of an aircraft, it is critical that the effects of bird or hail stone strikes on engine inlets and systems be investigated and mitigated to the greatest extent possible. A combination of experiments and numerical simulations is necessary to properly understand the behaviour of a bird or hail stone during impact and the reaction of the impacted material with the structure. A simulation methodology is developed and validated to certify the bird or hail stone strike resistance of composite air ducts designed for a new generation of jet training aircraft. Physical impact tests were performed on real composite parts. Numerical simulation results were compared with test results. Numerical simulation was also used for test preparation and optimization of the test rig design from the point of view of the influence of the stiffness of the surrounding aircraft structure. The validated modelling procedure allows the analysis of numerous impact scenarios, improving the optimization procedures for aircraft component design and reducing the cost of development by reducing the need to manufacture test prototypes.

Implementation and Evaluation of a Hail-Impact Simulation Device

“…This is a good choice for experiments with low impact-point-precision and impact-energy-accuracy requirements, such as testing hail-protection systems (27) or crop damage (3). This also works with medium precision and accuracy requirements, for instance testing solar panels (28), as well as jet engine air-inlet resistance to hail (29). An advantage of this impact simulation option is that it can take place in a regular-sized room.…”

Dynamic response of a material during a high-speed impact

“…This is technically demanding, but necessary for a numerical-model verification. 4 The use of high-speed load cells makes it possible to record the time-dependent force response of an impact event. However, the major difficulty of this approach is the existence of parasitic resonances.…”

“…The disadvantage of a standard square (or rectangle) specimen is the risk of non-regular flaws (Figure 1). 4 The specimen is typically over-loaded at the centers of the edges, causing the risk of cracks and disruptions, while damages of a specific form can appear in the corners. To avoid these types of flaws, we should use a round specimen as the optimum form is the circle.…”