Carbon-epoxy composite materials, due to their high strength in relation to mass, are increasingly used in the construction of aircraft structures, however, they are susceptible to a number of damages. One of the most common is delamination, which is a serious problem in the context of safe operation of such structures. As part of the TEBUK project, the Institute of Aviation has developed a methodology for forecasting the propagation of delamination. In order to validate the proposed method, an aerial structure demonstrator, modelled on the horizontal stabilizer of the I-23 Manager aircraft, was carried out. However, in order to carry out the validation, it was necessary to "simplify" the demonstrator model. The paper presents a numerical analysis conducted in order to separate from the TEBUK demonstrator model a fragment of the structure, which was used to study the delamination area, as an equivalent of the whole demonstrator. Subcomponent selection was carried out in several stages, narrowing down the analysed area covering delamination in subsequent steps and verifying the compliance of specific parameters with the same parameters obtained in a full demonstrator model. The parameters compared were: energy release rate values on the delamination front line and strain values in the delamination area. The numerical analyses presented in the paper were performed with the use of the MSC.Marc/Mentat calculation package. As a result of the analyses, a fragment of the structure was selected, which allows to significantly reduce the time and labour consumption of the production of the studied object, as well as to facilitate experimental research.
The article presents the results of research work performed under the TEBUK project, aiming primarily to develop a reference methodology for assessing the impact of damage on the strength of structures made of carbon epoxy prepregs. The tests described in the paper were concerned with a fragment of the structure (FS) of the TEBUK project demonstrator, made of carbon epoxy composite, with an artificial circular delamination measuring 40 mm in diameter. Numerical and experimental test of FS have been performed under quasi-static compression load. The buckling of the skin observed in the delamination area, as well as the propagation of the latter were investigated. The numerical calculations have been performed with the use of the commercially available MSC Marc/Mentat calculation suite based on the Finite Elements Methods. Results of the numerical calculations have been compared with experimental measurements made with the use of the Digital Image Correlation (DIC) method. The tests performed aimed to provide a preliminary verification of the numerical model. The results obtained have shown a very good correlation between the numerical and experimental results concerned with critical load levels at which stability of the layers separated by delamination is lost (buckling). The lack of convergence of the numerical model’s results after exceeding the critical load values has rendered it impossible to unequivocally compare the results concerned with propagation of the delamination area.
Dan Mihai Constantinescu, Radu Catalin Picu, Marin Sandu, Dragos Alexandru Apostol, Adriana Sandu and Florin Baciu
. Zhou, Y., Pervin, F., Lewis, L., Jeelani, S., Fabrication and characterization of carbon/epoxycomposites mixed with multi-walled carbon nanotubes, Materials Science and Engineering: A, Vol. 475, pp. 157-165, (2008).
7. Gkikas, G., Barkoula, N.-M., Paipetis, A.S., Effect of dispersion conditions on the thermo-mechanical and toughness properties of multi walled carbon nanotubes-reinforced epoxy, Composites Part B, Vol. 43, pp. 2697-2705, (2012).
8. Montazeri, A., Chitsazzadeh, M., Effect of sonication parameters on the mechanical
właściwości mechaniczne kompozytów węglowych, Prace Instytutu Lotnictwa, 2016, Nr. 3 (244) s. 65-73.
 Phadnis V. a., Makhdum F., Roy a. and Silberschmidt V.V., 2013, “Drilling in carbon/epoxycomposites: experimental investigations and finite element implementation”, composites Part a: applied Science and Manufacturing 47, pp. 41-51.
 Kaczorowska E., Dobór procesu kondycjonowania próbek zgodnie z wymaganiami kwalifikacji kompozytów polimerowych do zastosowań w konstrukcjach lotniczych, Prace Instytutu Lotnictwa, 2016, Nr. 3 (244) s. 85-91.
Prepregs, Key Engineering Materials , 598, 45-50.
8. Hiley M . (2000), Delamination between multi-directional ply interfaces in carbon-epoxycomposite under static and fatigue loadings, Fracture of Polymers, Composites and Adhesives, ESIS Publication 27 , 41-72.
9. Kim R. Y . (2001), Polymer matrix composite (PMC) damage tolerance and repair technology , Report No. UDR-TR-2001-00041.
10. Lander J. K., Kawashita L. F, Allegri G, Hallett S. R, Wisnom M. R. , (2010), A cut ply specimen for the determination of mixedmode interlaminar fracture
/epoxy composite and its protection structures suffered from lightning strike , Composite Structures, Vol. 145, pp. 226-241, Amsterdam 2016.
 Wang, F. S., Yu, X. S., Jia, S. Q., Li, P., Experimental and numerical study on residual strength of aircraft carbon/epoxycomposite after lightning strike , Aerospace Science and Technology, Vol. 75, pp. 304-314, Amsterdam 2018.
Reimar Unger, Philipp Schegner, Andreas Nocke and Chokri Cherif
effect of the strain rate on the tensile properties of carbon–epoxycomposite laminates. Journal of Composite Materials, 51(22), S. 3197–3210.
 Kwon, J. B., Huh, H., Ahn, C. N. An improved technique for reducing the load ringing phenomenon in tensile tests at high strain rates, S. 253–257.
 Naresh, K., Shankara, K., Rao, B. S., Velmurugan, R. (2016). Effect of high strain rate on glass/carbon/hybrid fiber reinforced epoxy laminated composites. Composites Part B: Engineering, 100, S. 125–135.
 Pariti, V. N. P. M. (2017). Mechanical behavior
Toughness in C/C Composites. Trans. Japan Soc. Engrs. 60-572A (1994), 978-983.
Rikards, R., A. Korjakin, F. Buchholz, H. Wang, A. Bledzki, G. Wacker. Interlanimar Fracture Toughness of GFRP Influenced by Fiber Surface Treatment. Journal of Composite materials , 32 (1998), No. 17 , 1528-1559.
Zhao, S., M. Gadke, R. Prinz. Mode I Delamination Behaviour of Carbon/epoxyComposites. J. Reinf. Plast. And Comp. , 14 (1995), No. 4 , 804-826.
Davies, P., C. Moulin, H. Kausch. Measurement of G
., Hardwick C.J., Haigh S.J., Meakins A.J., The interation of lightning with aircraft and challenges of lightning testing, Journal of Aerospace Lab , 5, AL05-11, 1-10, 2012.
 Feraboli P., Miller M., Damage resistance and tolerance of carbon/epoxycomposite coupons subjected to simulated lightning strike, Composites Part A: Applied Science and Manufacturing , 40(6-7), 954-967, 2009.
 Ranjith R., Myong R.S., Lee S., Computational investigation of lightning strike effects on aircraft components, International Journal of Aeronautical & Space Sciences , 15
properties of multiaxis 3D woven and 3D orthogonal woven carbon/epoxycomposites, Journal of Reinforced Plastics and Composites, 29(8), 1173-1186.
 Mohamed, M. H., Bilisik, A. (1995). Multilayered 3D fabric and method for producing, US Patent 5465760.
 Wichmann, M.H.G., Sumfleth, J., Gojny, F.H., Quaresimin, M., Fiedler, B., Schulte, K. (2006). Glass-fibre-reinforced composites with enhanced mechanical and electrical properties - Benefits and limitations of a nanoparticle modified matrix, Engineering Fracture Mechanics, 73(16), 2346