| Abstract [eng] |
The aim of this research is investigation of the application of non-destructive testing methods combination to defects in the composite honeycomb structure of the Mi-8MTV helicopter tail rotor blade. Helicopter Mi-8MTV tail rotor blade which consists of a spar, a segment made up of a skin and honeycomb filler, sparn end piece, an end fairing made from fixed and removable parts, an anti-icing system, heating strap and a unit for blade static balancing (balancing strips). The spari s manufactured of pressed aluminium profile with a constant section (airfoil NACA-230 M). Its inner outline has a constant section. The leading edge is machined in compliance with the blade theoretical outline. There are two parallel pads in spar root which are milled for end piece mounting. The end piece is made of high-tensile alloy steel and serves as blade fastening to the hub with four lungs and bolts. It is fastened to the par with eight bushings braced with bold and glued with film-forming glue. A bracked made of material AK-6 is glued to the spar rear wall in the root with the same film-forming glue. The tail rotor blade segment is glued to the spar booms and the rear wall in the root part. It is made up of upper and lower parts of glass plastic skin which thinkness is 0,4 mm. Upper and lower parts of glass plactic skin are glued to honeycomb filler with film forming glue. Blade skin consists of two layers of glass fabric. The honeycomb filler is glued up to of 0,04 mm thick aluminium foil, milled along theoretical outline and it forms hexahedral honeycombs with hexahedrom face of 5 mm. The end part of blade segment is finnished with an end edge glued to the skin and filler. Helicopter Mi-8MTV tail rotor blade hasa heating strap of the anti-icing system which consists of five glass fabric layers glued onto the spar and fixed along the blade leading edge. Heating elements are closed from the top with one layer of glass fabric and one layer of abrasive-proof rubber with is glued to the blade leading edge. Metal edge tipping is glued to the blade leading edge to procet the heating straps against its wear. To archieve the proposed research objectives, concepts for fabrication of artificial flaws were presented. Artificial flaws in tail rotor blade composite material structure were sucessfully manufactured using pneumatic gun „Crossman Classic 2100“ with 4,5 mm flat and pointed lead bullets, flat chisel with Ø0,55 cm round tip, 20 mm width sharp chisel to cut though tail rotor blade glass plastic skin and create honeycomb structure defects. Experimental studies using combination of non-destructive testing methods will be conducted in order to determine the effect of defects in fiber reinforced materials and honeycomb filler structure. The data extracted from these non-destructive testing techniques will be analyzed to draw conclusion about composite structure defect in the materials, which of them are problematic and require precaution as they evolve into delamination induced fracture causing flailure of the hole structure by progressively propagating through structure. The research presented is an innovative Non-Destructive Testing (NDT) methods combination technique which comprises of three non-destructive evaluation methods - 3D ultrasonic non-destructive method, active and passive thermograhy – for the purpose of detecting the inhomogeneities in the material and characterizing the material properties without destroying the serviceability of the part or system under investigation. The use of single non-destructive evaluation technique to evaluate the presence of defect or imperfection in a composite material component is not the most efficient way to draw conclusions. Integration of two or more non-destructive testing techniques, will always have a higher probability rate of flaw detection. Accurate data collection is necessary to estimate the size and location of the defects. |
