Korozja pokrycia samolotu i względy bezpieczeństwa konstrukcyjnego

The aim of this article is to point out some peculiarities of airframe corrosion, the impact of external forces on aircraft skin elements and their impact on structural integrity. The corrosion process is generally associated with fatigue of aircraft structural elements due to the effect of many factors such as the type of loading, the properties of the materials, the corro-sive environment, etc. The article is not focused on corrosion processes, but on load factors that are specific to aircraft wing design elements and their influence on corrosion of critical struc-tural elements. Corrosion of the wing is perceived as a consequence of environmental impact on damaged surface protection of the skin and connecting parts (rivets, screws, and welded joints) caused by static and dynamic stress of the wing and also by the interaction of the indi-vidual structural elements as a whole. The dynamics of operation of individual structural ele-ments is further enhanced by the fatigue of the material. Early detection of corrosion processes has generally been and is crucial to overall safety of the aircraft. The proposals presented in the article are formulated in order to improve the system of work to ensure the safety of aircraft operation in terms of resistance to corrosion damage.

Dynamic Behavior of Aviation Polymer Composites at Various Weight Fractions of Physical Modifier

The aim of this study was to determine the effect of a selected physical modifier with different granularity and mass percentage on the dynamics of aerospace polymer composites. The tests were carried out on samples made of certified aerospace materials used, among other purposes, for the manufacture of aircraft skin components. The hybrid composites were prepared from L285 resin, H286 hardener, GG 280T carbon fabric in twill 2/2 and alumina (Al2O3, designated as EA in this work). The manufactured composites contained alumina with grain sizes of F220, F240, F280, F320 and F360. The mass proportion of the modifier in the tested samples was 5% and 15%. The tested specimens, as cantilever beams fixed unilaterally, were subjected to kinematic excitation with defined parameters of amplitude and frequency excitation in the basic resonance zone of the structure. The results, obtained as dynamic responses, are presented in the form of amplitude–frequency characteristics. These relationships clearly indicate the variable nature of composite materials due to modifier density and grain size. The novelty of this study is the investigation of the influence of the alumina properties on system dynamics responses.

LIBS Monitoring and Analysis of Laser-Based Layered Controlled Paint Removal from Aircraft Skin

Reliability and controllability of selective removal of multiple paint layers from the surface of aircraft skin depend on effective online monitoring technology. An analysis was performed on the multi-pulse laser-induced breakdown spectroscopy (LIBS) on the surface of the aluminum alloy substrate, primer, and topcoat. Based on that, an exploration was conducted on the changes of the characteristic peaks corresponding to the characteristic elements that are contained in the topcoat, primer, and substrate with different layers of a laser action, in combination with analysis of microscopic morphology, composition, and depth of laser multi-pulse pits. The results show that the appearance and increase of the characteristic peak intensity of the Ca I at the wavelength of 422.7 nm can be regarded as the basis for the complete removal of the topcoat; the decrease or disappearance of the characteristic peak intensity can be regarded as the basis for the complete removal of the primer. Al I spectrum at the wavelength of 394.5 nm and 396.2 nm can be adopted to characterize the degree of damage to the aluminum alloy substrate. The feasibility and accuracy of the LIBS technology for the laser selective paint removal process and effect monitoring of aircraft skin were verified. Demonstrating that under the premise of not damaging the substrate, laser-based layered controlled paint removal (LLCPR) from aircraft skin can be achieved by monitoring the spectrum and composition change law of specified wavelength position corresponding tothe characteristic elements that are contained in the specific paint layer.

Pretreatment of CFRP by Amino Thermoset Abrasive Air Jet Machining

An effective pretreatment method of carbon fiber reinforced plastic (CFRP) aircraft skin was proposed. In this article, the function of the amino thermosetting abrasives entrained by the airflow on the CFRP aircraft skin is introduced and discussed to achieve the purpose of enhancing the coating adhesion and prolonging the service life. An orthogonal experiment with five factors and four levels was designed and carried out, including jet pressure, target distance and impact angle, moving speed and particle size. The best pretreatment process was obtained by analyzing surface morphology, wettability and adhesion. The erosion mechanism of CFRP coating pretreatment with abrasive impact was studied emphatically. The results show that the critical pressure for fiber damage is 0.4 MPa, and the better surface energy is 38.0 mN/m. Semi-ductile erosion has been identified as the main erosion mechanism of amino thermosetting abrasives eroding CFRP. Effective assurance was provided for the improved surface of the aircraft CFRP skin and enhanced coating adhesion in this study.