Research at UC3M improves the bolted joints in airplanes

Universidad Carlos III de Madrid
June 14, 2011

A research project at Universidad Carlos III de Madrid (UC3M) that analyses the bolted joints used in the aeronautical industry has determined the optimum force that should be applied so that they may better withstand the variations in temperature that aircraft are subjected to. This advance could improve airplane design, weight and safety. (OIC/UC3M)

The idea for this research arose when the problems of the large structural components of an airplane were being analyzed. These components are made up of a large number of different elements, which are themselves assembled using a variety of techniques, such as soldering, mechanical or adhesive bonding or a combination of these. Of these techniques, mechanical bonding is the method most commonly used in components made of composite materials. For example, the wing of an Airbus 380 alone is composed of over 30,000 elements, with approximately 750,000 bolted joints. These joints are of key importance since they form a weak point that can contribute to the breakage of the element, as well as increase the weight of the aircraft if the design is inefficient, thus raising the aircraft’s operating cost.

The researchers have analyzed the performance of these bolted joints in aeronautical structures in which mechanical elements (screws, nuts, washers) are used to join parts that are made of composite materials. Specifically, the scientists at UC3M have analyzed the influence of bolt torque (the force with which the bolt is tightened) and temperature, which varies from -50ºC, when the airplane is flying at an altitude of 10,000 meters, to 90ºC, the temperature to which a bolted joint may be exposed when it is close to a heat source. To do this, they developed a numerical model and analyzed the behavior of these joints under different conditions. "The main conclusion that we drew is that the torque of each joint should be estimated taking into account the range of temperatures to which the plate is going to be subjected, because current industry standards that are applied to determine torque do not take this effect into account", explains one of the authors of the study, Professor Enrique Barbero, head of the Advanced Materials Mechanics research group of the Department of Continuum Mechanics and Structural Analysis at UC3M, which has recently published the study in the Journal of Reinforced Plastics and Composites along with Professors María Henar Miguelez and Carlos Santiuste.

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