Repair of damage in aircraft composite sound-absorbing panels

This work is focused on analysis of mechanical behaviour of aircraft engine's sound-absorbing panels (SAPs) exposed to in-service damage. Its aim is to suggest techniques of local repair of damaged SAPs and estimation of their post-repair residual strength. Fibreglass laminate panels with tubular core and perforated elements were studied for this purpose. A mechanical behaviour of structural elements of the panels was modelled with the finite-element (FE) analysis, with through rupture considered as an in-service defect. A technique of defect repair without dismantling parts from the structure is introduced using a novel vacuumless technology. This procedure was implemented on specially produced samples and simulated with FE. Residual strength of repaired samples was compared with that of standard and ruptured ones in tension experiments and FE analysis. Conclusions about applicability limits of the presented method are provided

Investigation of the influence of perforation parameters on the acoustic efficiency of sound-absorbing structures

Within the framework of this work, calculation and experimental studies of the influence of technological defects on the acoustic efficiency of sound-absorbing structures (SAS) are carried out. In this work, the physical and mathematical models of predicting the effective acoustic properties of cells with different diameter of the throat were formulated. A series of laboratory experiments was performed to evaluate the acoustic efficiency of SAS cells with different diameters, on an interferometer with a normal sound wave drop. Based on the results of the studies, the dependences of the natural frequency of the resonator and the coefficient of acoustic pressure loss depending on the diameter of the perforation were revealed

SPECTRUM OF MOLECULAR GENETIC ALTERATIONS AND DIVERSITY OF CLINICAL FORMS OF STARGARDT DISEASE

Purpose of the study was to assess the spectrum of molecular genetic disorders and the variety of clinical forms in patients with Stargardt disease. Material and methods. 56 patients aged 15-44 years who had been diagnosed with Stargardt disease in a history or at the time of the examination were included in the study. All patients underwent standard complete ophthalmic examination, as well as high-performance parallel sequencing of the coding sequences and adjacent areas of the introns of the ABCA4, ELOVL4, PROM1 and CNGB3 genes, as well as of the minor exons of the ABCA4 gene. Results. Mutations in one of 4 genes ( ABCA4, ELOVL4, PROM1 and CNGB3 ) were detected in 46 of 56 patients (82.1 %). An inverse correlation was found between the duration of the disease and the loss of visual acuity per year for the three groups ( k = -0.86, k = -0.93, k = -0.63, p 31 year). A frequent mutation of the ABCA4 gene, p.G1961E was detected in 18 patients and in 83 % of cases (15 patients) is associated with a mild course of Stargardt disease. Complex mutation [p.L541P, p.A1038V] was detected in 17 patients, in 53 % (9 people) of cases was associated with more severe phenotype. However, in the compound heterozygous state with the missense mutation p.G1961E, a relatively mild course of the disease was observed. Conclusions. The loss of visual functions in Stargardt disease depends on the severity of the genetic defect in each case and on the disease’s duration in general