Ortasında delik bulunan eğrisel yüzeyli kompozit plakların burkulma davranışı

In this study, buckling behavior of E-glass/epoxy composite plate with curved surface having[±60o]2and [±75o]2orientation angles was investigated experimentally. As test material, 100- mm diameter composite pipeswere fabricated using filament winding processat±60o and±75o stacking sequences in Izoreel Firm.The composite specimens were trimmed using a diamond saw after pulling the pipe out of the mandrel. Test specimen lengths were 50, 65 and80-mm. Some of specimens were coded as “un-holed” the other specimens were holed using drilling machine with velocity of 350 rpm (Revolutionsper Minute) at three different central hole sizes such as 5, 10 and 15-mm. The buckling tests were carried out using Universal Shimadzu AG-X testing machine having 100 kN loading capacity at room temperature. In the tests, the cross-head speed of testing machine was chosen as 1 mm/min. The tests were performed using a specially designed and manufactured apparatus which was given in Figure 2. The aim of this study is to investigate the effect of the fiber orientation, hole diameter/width ratio (D/B=0; 0,17; 0,33; 0,5) and specimen length/thickness ratio (L/t=25; 32,5; 40)on curved composite plates. Each test parameter was repeated 4 times and average values were calculated. Critical buckling loads were obtained for all of test data. Figures were created by test data for better understanding of buckling behavior of E-glass/epoxy composite plates.Then these figure curves were compared. As an example images of damaged specimens with ±75oorientationare given in Figure 6-8. These damage cases are evaluated. As a result, it is seen that the fiber orientation, D/B and L/t ratios of test specimens have significant effects on the critical buckling loads of curved composite plates. Also, a similar effect was seen on the damage images. Critical buckling loads increase with changing fiber orientation (from ±60oto ±75o). The buckling loads decrease by increasinghole diameter with holed specimens with comparing un-holed specimens. So in serves, hole diameter in the buckled composite plates should be taken into consideration. The critical buckling loads of the composites decrease by increasing specimen lengths due to reduction stiffness. Therefore, decrease in buckling resistance was leaded to buckling at lower loads. A similar trend was obtained in the buckling damage areas.