Static Tests of Wing Box of Composite Aircraft Wing Using Acoustic Emission and Strain Gaging
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STIC METHODS
Static Tests of Wing Box of Composite Aircraft Wing Using Acoustic Emission and Strain Gaging A. N. Ser’eznova, L. N. Stepanovaa, b, *, A. S. Laznenkoa, S. I. Kabanova, V. L. Kozhemyakina, and V. V. Chernovaa, b a
Siberian Aeronautical Research Institute Named after S.A. Chaplygin, Novosibirsk, 630051 Russia bSiberian Transport University, Novosibirsk, 630049 Russia *e-mail: [email protected] Received May 7, 2020; revised June 9, 2020; accepted June 10, 2020
Abstract—Static tests of a two-spar T800 CFRP wing box have been carried out. The object was tested when loaded using the methods of acoustic emission (AE) and strain gaging. Strain in the material was determined in real time in the areas where strain gages were bonded (the panels of wing box, the walls of side members, and the shelves of stringers). The elements of the wing box have been established in which nonlinear strain change is observed and residual deformations are recorded after unloading. The AE method has been used to localize the sources of signals. The coordinates of the sources corresponded to the location of the third rib. Clustering recorded AE signals based on their digitized form has made it possible to group the signals and assign them to sources that correspond to structure failure. It is shown that in the process of loading the wing box, an increase in the structural coefficient of AE signals corresponding to CFRP delamination in the location zone is observed. Keywords: wing box, carbon fiber reinforced plastic, acoustic emission, static loading, strain gage, strain gaging, location, clustering DOI: 10.1134/S1061830920080094
INTRODUCTION Full-scale tests of aviation composite structures using strain gaging and acoustic emission (AE) allow one to investigate the strength characteristics of these structures and draw conclusions about the level of deformations at given loads, to identify flawed zones and determine their coordinates and hazardousness [1–10]. AE signal sources are located in real time, when the structure is under load. AE signals are highly informative and related to the deformation of objects [11–15]. Structures made of composite materials (CMs) are difficult to test by the AE method, since their material is characterized by structural inhomogeneity, anisotropy of properties, and the diversity of types of reinforcement. In terms of their hazardousness, defects in CMs are classified into four groups. The first group is associated with defects produced in the undercured polymer matrix. In this case, heat resistance decreases, moisture resistance deteriorates, and the nature of material failure under static, cyclic, and shock loading changes. The second group of defects includes delamination. When compressed, material with delamination may lose strength depending on the depth of the delamination and its size. The third group includes cracks, which violate the integrity of the composite and can lead to delamination of the CFRP material. The fourth group consists of chips, notches, and holes that reduce the bearing cap
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