Dairesel delikli kompozit levhalarda gerilme yığılmalarının incelenmesi

Öz

Bu çalışmada, tek eksenli gerilmeye maruz düzlemsel olarak yüklenmiş ve ortasında dairesel delik bulunan kompozit levhalarda delik kenarlarında meydana gelen gerilme yığılmaları hesaplanmıştır. Hesaplamalarda dört tabakalı Grafit/Epoksi kompozit levha kullanılmıştır. Gerilme yığılması hesaplamaları Sonlu Elemanlar Analizi kullanılarak yapılmıştır. Sonlu Elemanlar Analizi ANSYS(v.12.01) yazılımı kullanılarak gerçekleştirilmiştir. Gerilme yığılmalarını doğru olarak hesaplayabilmek için ağ yapısının etkinliği yakınsama testi yapılarak belirlenmiştir. Delik çevresindeki etkin eleman sayısı belirlenerek ağ yapısı her bir model için oluşturulmuştur. Maksimum gerilme bulunmuş ve ortalama gerilmeye bölünerek gerilme yığılma faktörü hesaplanmıştır. Bulunan sonuçlar literatürde yer alan sonuçlar ile karşılaştırılmıştır. Ayrıca, fiber takviye açısının ve levha genişliğinin gerilme yığılmalarına olan etkisi incelenmiştir. Fiber açısının 450 civarında tutulması, gerilme yığılması açısından büyük avantaj sağlamıştır. Sonuçta, takviye açısı ve levha genişliği/delik çapı oranı arttıkça gerilme yığılmasının azaldığı görülmüştür. Gerilme yığılması azalırken, çekme eksenindeki Elastisite Modülü de düştüğünden dolayı malzemenin mukavemeti azalmıştır.

Anahtar Kelimeler

• Kompozit malzemeler, Gerilme, Gerilme yığılması, Fiber takviye açısı, Ansys

The investigation of the stress concentration in composite plates with a circular hole

Öz

In this study, the stress concentrations of composite plate have been investigated numerically by static tensile test. The stress concentrations that occurred at the vicinity of the hole that centered on a laminated composite plate which is exposed to one axial load have been calculated. Four layered Grafite / Epoxy composite plates have been used in calculates. In order to calculate of stress concentrations was by using Finite Element Analysis. The Finite Element Analysis was executed with ANSYS (v.12.01) software program. In modeling, Shell 99 elements were used. The analysis on the different diameter of the plate (10 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm and 90 mm) has been examined for 9 different types in the stress concentrations. Effects of the fiber reinforcement angle has been investigated for the plate with layer 00, 50, 100, 150, 200, 250 , 300,350, 400, 450, 500, 550, 600, 650, 700, 750 , 800, 850 and 900 . The fiber direction of 00 was adopted to parallel the axis of the samples. Uniaxial tensile stress was performed to applying to each model 1 MPa. Effects of the hole diameter and fiber reinforcement angle has been investigated for concentrations of stress. In order to calculate accurately of the stress concentrations have been determined by the convergence test of effectiveness of the mesh. Then, for each model has been created by determining the number of active mesh elements around the hole. The number of active elements in the around holes was found to as 200. Thus, the maximum stresses formed in the material were found and the factor of stress concentration is calculated by dividing to the average tensile. These values are compared with the values calculated by Lekhnitski (1968) analytical method. The obtained results were compared the studies available in the literature. Besides, the effects of fiber orientation angle and plate’s width on the stress concentration have been analyzed. As a result, the stress concentration was found to be decreased with the increase of the ratio between fiber orientation angle and plate’s width to the diameter of the hole. The results showed that we need different approaches to improve the stress concentrations. To get the higher performance, more effective methods should be improved. In the future work, we focused on this problem. As a continuation of this work was seen that instead of a single hole on the composite plate of two adjacent holes the smaller diameter will change to the extent to which strength what would be the most appropriate level of distance between the centers of hole and what can be done in the case of the analytical solution is not possible, and can be done in the case of the analytical solution is not possible.

Anahtar Kelimeler

• Composite Materials, Stress, Stress Concentration, fiber orientation angle, Ansys.