Çentikli kompozit levhaların hasar davranışlarının incelenmesi

Abstract

Bu çalışmada, çentikli kompozit levhaların hasar davranışları statik çekme testleriyle deneysel olarak araştırılmıştır. Sekiz tabakalı örgülü cam elyaf takviyeli epoksi reçine matrisli kompozit levhalar kullanılmıştır. Levhaya kenarlarından ve ortasından açılan çentiklerin ve fiber takviye açısı değişiminin levhanın çekme mukavemeti üzerine etkileri incelenmiştir. Fiber takviye açısının etkileri [0o]8, [15o ]8, [30o]8, ve [45o]8, tabaka dizilimine sahip levhalar için araştırılmıştır. Çentik türü değişimi ise levha ortasında radyal delik (Tip 1), levha kenarında yarım daire çentik (Tip 2), levha merkezinde dairesel delik (Tip 3) ve levha kenarında u çentik (Tip 4) olmak üzere 4 farklı çentik türü için incelenmiştir. Fiber takviye açısına bağlı olarak tüm çentik türleri için hasar yüklerinin azaldığı gözlemlenmiştir. Buna ek olarak çentik türü değişiminin hasar yükleri üzerinde oldukça etkili olduğu deneysel çalışma sonuçlarından görülmektedir.

Keywords

• Tabakalı kompozit levhalar, hasar analizi, çentik etkisi.

Investigation of Failure Behaviors of Notched Composite Plates

Abstract

In this study, the failure behavior of notched composite plate has been investigated experimentally by static tensile test. Eightlayered woven glass fiber reinforced epoxy resin matrix composite plates have been used. Notch opened on the middle and by the side of plates and their effects on the tensile strength of the fiber reinforcement plate angle changing has been examined. Effects of the fiber reinforcement angle has been investigated for the plate with layer [0o ]8, [15o ]8, [30o ]8, and [45o ]8. Radial hole in the middle plate (Type 1), semicircular notch on the plate edge (Type 2), a circular hole in the plate center (Type 3) and U notch on the plate edge (Type 4) has been examined for 4 different notch types. Reducing of the failure loads has been observed for all notch types depending upon the fiber reinforcement angle reducing. In addition, that notch type changing is quite effective on failure loads have been seen from the experimental results. 3 samples has been produced in the laboratory and they has been used for each parameter. All samples has been fixed to the jaws of 100 kNInstron 8800 tensile machine and tests has been carrying out under the room temperature conditions. Tensile test speed has been applied as 1 mm / min. While testing, failure loads and elongations have been recorded to the computer automatically and this data has been used in the desired graphics. Failure loads has been reducing depending on the reducing of fiber reinforcement angle, whereas the elongation rate has been increasing significantly. Elongation rate has been decreasing because of effect notch. [0o ]8 plates has been breaking suddenly without significant elongation but failure has been incurring with elongation for the other angels. Alongation to the other supplements has been realized with a sudden breakage occurs with prolonged failure. The maximum failure load value were measured as 7297.32 N for [0o ] 8 Type3 notch type. The minimum failure load was measured as 1475.50 N for [45o ]8 Type1 notch. Notches on the composite plates led to a decline as varying from 78% to 40.4 % rates. If we make a generalization; Type1 in terms of all fiber reinforcement angels provides the largest decline according to the reduction of failure to the loads and the decrease in load failure is seen to range between 75.5% and 78% . Type4 failure reduction rate is close to the value of Type1 , but less than Type 1. Type3 has 50% average reduction on failure loads. Type1 and type4 have the maximum reducing rate. the change of the fiber reinforcement angle is the most important parameter to determine the failure loads. General results from this study; Failure loads have been decreasing due to the fiber reinforcement angle increasing. It has been observed that elongation increased due to the fiber reinforcement angle increasing. The first failure of the material has been occurring earlier due to fiber reinforcement angle increasing and after resin hardens immediately, failure progressing time has been increasing. That changes of notch types are important on the failure loads has been seen. Elongation has increased depending on the notch geometry. Sudden breakages carry out at [0o ]8plates, these type breakages are unwanted conditions in terms of types in the structures because of sudden. Ductile fracture has been carrying out in the angled plate and there has been an significant increasing in the elongation before complete breakage. Type1 equals to Type4; Type2 equals to Type3 about geometric dimensions. Different notches locations cause to different failure load values. Failure load of a circular hole in plate center (Type 3) is bigger than plate edge semicircular notch (Type 2). This result is already expected because of central notch performance. U notch on the plate edge (Type 4) is bigger than semicircular notch on the plate edge (Type 2).

Keywords

• Laminated composite, failure analysis, notch effect.