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Öğe The effects of stacking sequence on drilling machinability of filament wound hybrid composite pipes: Part-2 damage analysis and surface quality(ELSEVIER SCI LTD, 2020) Gemi, Lokman.; Morkavuk, Sezer.; Köklü, Uğur.; Yazman, Şakir.In the first part of this two-part study, filament wound hybrid composite pipes with various stacking sequences were manufactured and mechanical properties such as hardness, ring tensile strength, and burst strength were experimentally investigated. After determining mechanical properties, drilling tests were performed to research machinability characteristics. The second part of the study consists damage analysis and surface quality examination including ring test damage analysis, push-out delamination analysis, borehole damage examination and borehole surface quality. The experimental data suggested that cutting parameters, stacking sequence, and the use of back-up were impactful on the formation and propagation of various types of damages. Especially, the effect of stacking sequence was remarkable. A larger delamination area was formed in Glass-Glass-Carbon (GGC) sample after the ring tensile tests compared to Glass-Carbon-Glass (GCG) and Carbon-Glass-Glass (CGG) samples. In all cases, the utilization of back-up lead to decrease of delamination with 9-40% reduction in surface roughness. When the back-up is not used during drilling, an excessive push-out delamination occurred in all drilling tests. Moreover, CGG samples represented lower push out delamination. In addition, position of the hole depending on the winding angle plays a key role on damage formation and surface quality.Öğe Experimental investigation of shear capacity and damage analysis of thinned end prefabricated concrete purlins strengthened by CFRP composite(ELSEVIER SCI LTD, 2019) Gemi, Lokman.; Aksoylu, Ceyhun.; Yazman, Şakir.; Özkılıç, Yasin Onuralp.; Arslan, Musa Hakan.Prefabricated structures supported with purlins are exposed to numerous damages due to the excessive snow loadings as vertical loadings. The thinned regions of the purlins are responsible with the failure of the structure since the shear cracks usually initiate at these regions and propagate along with the purlins, and as a result, a total collapse may occur. In this study, carbon fiber reinforced polymer (CFRP) composites with four different configurations (P-2-P-5) were employed for strengthening prefabricated purlins in order to increase the strength of the purlin against shear damage generated under vertical loading. The load carrying capacities and damage patterns of the purlins were compared. The failure of the reference purlin (P-1) was occurred as a shear damage at the thinned regions before reaching its bending capacity. However, the failure characteristic of the CFRP reinforced purlins was dominated by the bending damage and the vertical loading capacity of the purlins were increased up to 59% depends on the CFRP wrapping. Damage analysis of the CFRP composite was also performed. Various damage modes of the structure such as cover separation, air voids, delamination, debonding, fiber bundles breakage, matrix cracks, fiber bundles debonding, fiber breakage and buckling were observed and explained thoroughly.