Experimental and numerical studies on low velocity impact behavior of Glare panels

Abstract

The aerospace industry is always striving to improve aircraft efficiency and strength capacities. New materials are constantly being researched in order to produce more durable and lighter structural parts. Glare materials, which are obtained by laying glass fiber resins in certain directions between thin aluminum sheet metal parts, are very promising, especially in terms of fatigue and impact damage resistance. Glare, which was used in the fuselage panels of the Airbus A380 aircraft, has provided many advantages to the aircraft in many respects. It is known that aircraft are subjected to many low-speed impact damages during their manufacturing and service life such as tool drop, impact of foreign objects on the runway. These damages are also a design criteria to be considered during aircraft design. In this thesis, low velocity impact tests were performed on test specimens made of Glare 4A-2/1-0.3 material in accordance with the standards. Calibration tests were performed to determine the critical damage level and then verification tests were performed to examine the critical energy level. At the same time, a numerical model was prepared with the finite element method to verify the tests in Abaqus/Explicit program. In the model, three-dimensional solid elements were used and the interlaminar behavior was created using cohesive surfaces. The solution algorithm of the Abaqus/explicit program was created with the help of a VUMAT code and the damage criterion for composite plates was embedded in this code. The results of the simulation studies were compared with the results of the experimental studies and consistent results were observed within certain error rates. After the numerical results were verified, the finite element models were updated and the effects of various parameters such as plate thickness, energy level, metal thickness and impact angle on low velocity impact damage were investigated. As a result of the studies carried out, the parameters examined were evaluated and preliminary evaluations were made regarding the use of Glare 4A-2/1-0.3 material for aircraft structure in terms of low-velocity impact resistance. Considering the low velocity impact damage, it was concluded that Glare 4A materials can be evaluated in addition to traditional metallic structures and composite structures at the material selection stage for aircraft structural design. The studies concluded that increasing laminate thickness results in more lightweight structures than increasing outer Al thickness. Moreover, considering oblique impact conditions, it was seen that dent depth and panel failure is proportional to the impact perpendicularity. Finally, it was stated that there are many research areas that need to be examined regarding Glare materials. Some suggestions for the future research and studies were mentioned.