Theses supervised by Prof. Dr. Onur Sayman
15 theses · Dokuz Eylül University
Failure analysis of bolted and pinned composite joints under temperature effects
In the first part of the study, experimental failure analysis has been carried out to determine the effects of high temperatures and tightening torques on the failure load and failure behavior of single lap double serial fastener glass fiber / epoxy composite joints. 40, 50, 60, 70, and 80 degrees centigrade temperatures were exposed to the specimens during tensile tests. It was seen that, the load-carrying capacity of the joint is decreased gradually by increasing temperature level. In proportion to the room temperature, the maximum decrease of failure loads occurs at 70 and 80 degrees centigrade with the rate of nearly 55 and 70 percent respectively, because of the heat damage to the resin matrix. In the second part of the study, experimental investigations were conducted on failure responses of single lap double serial fastener joints in glass fiber / epoxy composite laminates when subjected to low temperature environment. The results of experiments, implemented at five different low temperature levels ranging from 0 to -40 degrees centigrade, were evaluated in comparison with room temperature tests. Joints exhibited relatively higher load-carrying capacities with increased stiffness by decreasing temperature. Both in the first and second part of experiments, bolts were fastened under M= 6 Nm and M= 0 Nm (finger tightened) torques in order to examine tightening torque effects at each temperature condition. As expected, a greater amount of bearing load could be carried by the joints with pre-tightened fasteners. The results proved that, tightening torque is still effective at elevated and low temperature conditions, Furthermore, any reduction in temperature at subzero degrees centigrade is observed to lift the effectiveness of tightening torque on the joint strength. In addition, bearing mode, the most desirable failure type in mechanically fastened joints was monitored as the main failure mode, regardless of the temperature exposed.Keywords: glass fibers, composite joints, high temperature, low temperature
Alt ekstremite protezlerinde farklı yükleme etkilerinin araştırılması
Bu çalışmada, hasarlı ayak bileği eklemlerinde kullanılan total ayak bileği protezleri incelenmiştir. Çalışmanın ilk bölümünde ayak-ayak bileği kompleksinin anatomisi ve biyomekanik özelikleri anlatılmıştır. Daha sonra günümüzde yaygın olarak kullanılan total ayak bileği protezleri ve protezlere ait çalışma sonuçları incelenmiştir. Çalışmanın ikinci bölümünde total ayak bileği protezlerinin ayak-ayak bileği kompleksinin davranışları üzerindeki etkileri sayısal ve deneysel yöntem olmak üzere iki ayrı şekilde incelenmiştir. Çalışmanın nümerik araştırma bölümünde, BT (Bilgisayar tomografisi) görüntüleri ile MIMICS ve SOLIDWORKS programları kullanılarak normal ve protezli ayak-ayak bileği kompleksine ait kemikler, yumuşak dokular ve protez bileşenlerine ait katı modeller hazırlanmıştır. Daha sonra bu modeller ABAQUS programına aktarılmıştır. Normal ayağa ait SEA (sonlu eleman analizi)' nde, kemikler ile kıkırdaklar arasındaki ve yumuşak doku ile zemin arasındaki etkileşimler kayan temas parçaları olarak tanımlanmışken yumuşak doku ile kemik yüzeyleri arasındaki etkileşimler yapışık temas parçaları olarak tanımlanmıştır. Buna ek olarak protezli ayak bileği için protez bileşenleri arasındaki ve protez bileşenleri ile tibia ve talus arasındaki etkileşimlerde kayan temas olarak tanımlanmıştır. Dengede duruş pozisyonu için modele ait statik analiz yapılmış ve normal ve protezli ayak bileklerine ait gerilme, gerinme ve plantar basınç dağılımları karşılaştırılmıştır. Çalışmanın deneysel kısmında, hazırlanan bir bası deney düzeneği yardımıyla değişik duruş pozisyonları için kadavra bir ayağın normal ve total ayak bileği protezli durumlarına ait kuvvet deplasman değerleri incelenmiştir. Son olarak normal ve protezli ayaklar için elde edilen nümerik ve deneysel sonuçlar karşılaştırılmıştır.
Failure analysis in an adhesively bonded single-lap composite joint under various loads
In this study adhesively bonded composite single-lap joints are investigated experimentally. Different surface properties, different curing temperatures of the adhesive, and the effects of different adhesive thickness on the composite joint strength are investigated. First, mechanical properties of the adhesive and adherend are investigated. Then tensile tests, axial impact tests, transverse impact tests and four point bending tests are conducted, respectively. All of these test are made in different conditions like operation temperature, surface quality, curing time, impact energy etc. Finally, after these series of the tests, for having good strength in different conditions, joint modifications are studied and some configurations are made on the composite joint and tested. This study showed that adhesive thickness, curing temperature, surface quality, operation temperature and impact energies have an important effect on the composite joints. Generally these effects were adverse but in some conditions these effects were useful. Additionally to the failure analysis, in this study, we used these useful effects to modify composite joints and we developed high strength composite joints in higher operation temperatures.
Determination of composite pressure vessels under various loadings
The aim of this study is the investigation of optimal angle-ply orientations of antisymmetric composite pressure vessels with a plastic liner designed for maximum first-ply failure and burst pressures at 2, 25, 60 and 80 degrees centigrate temperatures.
Behaviour of composite materials under impact loading
In this study, low velocity impact tests on the glass/epoxy, carbon/epoxy and glass/carbon hybrid laminated composite plates at 20, 90 and -50 °C temperatures were performed to investigate impact behaviors of the laminates. Impact responses of the composite specimens were characterized in terms of impact parameters such as permanent deflection, maximum contact force, maximum contact time, energy to maximum contact force, and total energy absorption at low, intermediate, and high impact energy levels. Energy profile diagrams and force versus deflection curves were plotted for each temperature and specimen type. Impact tests on the saturated specimens kept in seawater for 7 months were also conducted at the same impact energy levels as that of dry specimens. The initial damage, perforation and propagation energies were obtained for each temperature and specimen type. The impacted specimens were observed by visual inspection. A high-intensity light was used to identify the projected delamination areas in the impacted glass/epoxy composite laminates. The photographs of the cross-sections of the impacted specimens were taken. Delaminated surfaces were observed by an optical microscope. There point bending tests on the impacted specimens were also performed. In addition, mechanical properties of unidirectional glass/epoxy and carbon/epoxy composite plates were determined at 20 and 90 °C temperature. Thermal residual stresses at 20, 90 and -50 °C temperatures were obtained by using ANSYS software and the effects of the residual stresses on matrix cracking damage before impact were analyzed. The results showed that impact behaviors of the laminated composites were affected by the different environmental conditions.
Bolt-hole tightening effects in single-lap composite bolted joints
The weight and fuel savings offered by composite materials make them attractive not only to the military, but also to the civilian aircraft, aerospace, and automotive industries, where bolting joints are extensively used as a primary method of forming structural joints. Single-lap joints have good accordance with real conditions in comparison with other joint types. Therefore, the main objective of this paper is to investigate the behavior of single-lap joints in glass fiber reinforced epoxy (GFRE) composites under tension and pure bending loading conditions, with a constant W/D ratio (3) and variable the E/D ratios (3, 4, 5) and tightening torque values (0, 3 and 6 Nm). First, the mechanical properties of the composite were determined experimentally using the ASTM testing standards. Bending properties were determined using four-point bending test. Finally, special test fixtures were designed to facilitate the study of the effect of bending on the composite bolted joints.The experimental results show that in the tension tests, with increasing E/D ratio and tightening torque, the value of failure bearing stress increased. But, it seems that, this is not always true for continuous increase of these parameters. And in the bending tests, it is seen that at zero torque, with the increase of the E/D ratio the bending strength value increases, but this increase is small at T=3, 6 Nm torques. And in these tests, the joint failed at the center, near the bolt, because of the excessive delaminations on the compressive side.
Failure analysis of composite joints under preload moment and moisture.
In this study, a failure analysis was performed under various conditions numerically and experimentally to investigate the behavior of laminated composite plates which have pin-loaded holes. The main aim of the study is searching the effects of preload moment, moisture and interference-fit on bearing strength, failure load and failure mode in pin-jointed and bolted carbon-epoxy composite plates which were subjected to a traction force. Some of the specimens were kept in the seawater for sixty days before the experimental tests to observe the effect of moisture.Each laminated plates consisted of four laminas and had same stacking sequences. Two different geometrical parameters, end distance to pin diameter ratio and width to pin diameter ratio were considered. End distance to pin diameter ratio and width to pin diameter ratios were determined ranging from one to four and from two to four, respectively. The pre-load moments were applied to the specimens as three and six newton-meter for observing the failures under preload moment. Also, for investigating effect of interference-fit, a pin was produced which has a bigger diameter than hole diameter.The experiments were performed in tension mode on the Instron-1114 Tensile Machine of a crosshead speed of 1mm per minute. Then the average bearing strength values were found. The load versus pin displacement curves were plotted in the experiments. For the numerical study, three-dimensional non-linear contact analyses were conducted using commercial program ANSYS v10.
Kolon altı sismik izolatör kuvvet analizi
Günümüzde birçok betonarme ve çelik yapı, depremlerin yıkıcı ve hasar verici etkilerine karşı ne yazıktır ki korumasızdır. Birçok mimari yapı, mimari bir zorunluluğun gereği veya yapının kullanım amacının gereği olarak, asimetrik bir planda yapılmaktadır. Simetrik plana sahip olan birçok yapıda ise, kütlelerin eşit olmayan dağılımı söz konusudur. Yapıların planındaki asimetriklik ve yapıdaki düzgün olmayan kütle dağılımı, deprem hareketi sırasında yapıda burulma momentlerine neden olur. Yapıda deprem nedeniyle meydana gelen bu burulma, yapının düşey taşıyıcı elemanlarında ilave kesme kuvvetleri oluşmasına sebep olur. Bu ilave kesme gerilmeleri de, yapının kütle merkezinin yapının rijitlik merkezinden uzaklaşma oranına bağlı olarak büyür ve bu ilave gerilmeler sayesinde, yapıda ciddi hasarlar olabilir. Depreme dayanıklı yapıların tasarımında, geleneksel yaklaşıma göre; yapıları bu tür hasarlardan korumanın yolu, projede simetrinin olması ve rijitlik merkezi ile kütle merkezinin aynı düşey eksen üzerinde olmasına dikkat edilmesidir. Ancak, günümüzde, her geçen gün daha fazla uygulama alanı bulan modern yaklaşımda ise, bu tür yapıların depremsel davranışı, yapısal kontrol mekanizması kullanılarak iyileştirilebilir bir durumdur ve böylece yapılardaki depremsel hasar oluşma riski en aza indirililir. Bu çalışmada, binaların deprem nedeniyle meydana gelen kuvvetlerin etkisi altında, elastomer esaslı deprem izolatörleri kullanarak taban yalımı yapılmış yapıların davranışlarının kontrol altına alınmasının faydaları üzerinde durulmuştur. Yapıların deprem yalıtımında kullanılan elastomer esaslı deprem izolatörleri üzerinde deprem nedeniyle oluşan kuvvetler incelenmiştir. Özellikle, betonarme ve çelik yapıların depremin zarar verici ve yıkıcı etkilerini önlemek amacıyla geliştirilen ve binaların ve köprülerin kolonları ve kirişleri altına yerleştirilerek taban yalıtımı yapımında kullanılan "Elastomer Esaslı Deprem İzolatörlerinin" kuvvet ve gerilme analizlerinin yapılması bu doktora çalışmasının ana konusudur. Bu çalışma ile kolonların altına yerleştirilen deprem izolatörlerine gelen kuvvetlerin analizinden hareketle performansı yükseltilmiş olan elastomer esaslı yeni nesil deprem izolatörlerinin geliştirilmesi amaçlanmıştır. Bu çalışma kapsamında kurşun Çekirdekli LRB tipi elastomer esaslı deprem izoltörlerine alternatif ELRB tipi elastomer çekirdekli izolatörler geliştirilmiştir ve bölüm yedide ayrıntılı bir şekilde bilgi verlmiştir.
Failure analysis of composite bolted joints under corrosive effects
In this study the effect of water absorption and corrosive sea water on the failure response of an angle ply glass fiber reinforced-epoxy composite oriented as [0/0/90/45]s has been experimentally investigated. Two geometric parameters were chosen for failure response of the bolted?joint composite laminates. Those were the edge distance-to-hole diameter ratio (E/D) and the plate width-to-hole diameter ratio (W/D), which were selected from 1 to 5 and from 2 to 5.The specimens were first tested for unimmersed condition, afterwards another group of specimens were immersed into sea water for 200 days. The experiments were performed using some parameters for the pinned and bolted specimens. The specimens were tested under pre-load moments as, 0 and 3 Nm and 6 Nm. The experiments have not been stopped until a failure occurs on specimens. Interpretations have been made by relying on the bearing strength and displacement diagram.Tables include failure loads with their failure type obtained as a result of the experiments and tables show the comparison failure load for unimmersed and immersed specimens under preload moments are given. The results point out that immersion of the composite specimens into the sea water under preload moments can cause a notable decrease on the failure load.
Pim yüklü kompozit plakalarda hasar analizi
The aim of this study is to search the failure load, bearing strength and failuremode in an aluminum-glass epoxy sandwich composite plate subjected by a boltimpacted by a preload and washer on a circular hole. In experiments without apreload moment, the hole of the plate exposed to a traction force by a rigid pin.Parametric studies were performed by experiments to find the effects of jointgeometry and preload moment on the failure load and failure mode. The preloadmoment (M), end distance to diameter (E/D) and width to diameter ratios (W/D)changed from 0-3-6 Nm, 1 to 5 and 2 to 5 sequentially. During the numerical andexperimental study, orientation angle ? hold constant at 0 o. The failure analysis isperformed both numerically and experimentally.From the results of this study, it is observed that with increasing of M, E/D, W/Dthe bearing strength increases; and when M = 0-3-6 Nm, E/D = 2-3-4-5 and W/D = 5full bearing mode occurs. When E/D = 1 the failure mode is always Shear-out for allparameters.Lusas 13.6 finite element analysis program was used for numerical study. Threedimensional finite element method was taken as a base. Maximum failure load wasobtained with non-linear analysis and Hashin failure criteria was used.In the case of failure, appropriate properties of failure mode was reduced.By the help of standard tests, composite material?s mechanical properties weredetermined.From the comparison of the numerical and experimental studies sensibleagreement was seen between the results where full bearing mode observed.
Prediction of composite vessels under various loadings
In this study, resistances of the composite pressure vessels under internal pressure wereinvestigated. Study deals with the influences of temperature and winding angle on filamentwoundcomposite pressure vessel with a plastic liner. An elastic solution procedure based onthe Lekhnitskii 's theory was developed in order to predict the first-ply failure of the pressurevessels. The analysis accounts for the failure pressure for various orientation angles underuniform temperature. The Tsai-Wu failure criterion was applied for the checking the first-plyfailure of layers in a simple form. In addition, the von-Mises criterion was used in order tofind the failure of the plastic liner. The solution was presented and discussed for variousorientation angles with or without failure of the plastic liner.The layers were oriented symmetrically and antisymmetrically for [30o/-30o]2, [45o/-45o]2,[55o/-55o]2, [60o/-60o]2, [75o/-75o]2 and [90o/-90o]2 orientations. The hygrothermal and othermechanical properties were measured on a epoxy-carbon composite layer. Some analyticalsolutions were compared with the finite element solutions, in which commercial softwareANSYS 9.0 was utilized, and close results were obtained between them. In the numericalsolutions the temperatures influence was found ineffective for the burst pressure. Theoptimum winding angle for the composite pressure vessel analysis with the internal pressureloading case was obtained as 54o for laminates and as 90o for a lamina.
Non-linear stress analysis in pin joints
The scope of this study is to investigate the failure load, failure mode and bearing strength in a glass epoxy laminated composite plate carried out by a bolt impacted by a preload and washer on a circular hole. During experiment processes without a preload moment the hole of the plate exposed to a traction force by a rigid pin. Parametric studies were carried out by experiments to obtain the effects of joint geometry and preload moment on the failure load and failure mode. The preload moment, end distance to diameter ratio and width to diameter ratio are chosen from 0, 2.5 and 5 Nm, from 1 to 5 and from 2 to 5, respectively. In addition, 4 different laminated composite plates were also investigated as changing of orientation angle. The failure analysis was carried out both numerically and experimentally. Additionally, mechanical properties of laminated composite material are measured using standard test methods. According to results of present study, it was examined that with increasing of M, E over D, W over D the bearing strength increases; and when M 0, 2.5 and 5 Nm, E over D 2, 3, 4, 5 and W over D 5 full bearing mode were occurred. Meanwhile E over D is equal to 1 the failure mode was constantly as shear-out mode for all parameters. Numerical study was performed using LUSAS finite element code. Maximum failure load was calculated with non-linear analysis and using Hashin failure criteria. When it was done a comparison between numerical and experimental results, a good agreement was observed. Keywords: Laminated composite plate, glass-epoxy, failure strength, failure mode, preload
Kare delikli kompozit malzemede elsto-plastik gerilme analizi
IV ABSTRACT In this study, the elasto-plastic stress analysis of composite plates with a square hole has been obtained. Finite element method has been used to solve the problem. Isoparametric rectangular element with nine nodes has been chosen. The automatic mesh generation has been taken place in finite element model and the special computer program has been developed to solve the problem. The engineering constants of composite material have been obtained by using strain gage in the tensile testing machine after production of the material (Stainless steel- aluminum composite). Finally, in this study, the distribution of the plastic region in the vicinity of the hole has been studied for different uniform loads, different hole diameter and different orientation angles. Furthermore, the plate is stronger because of resultant residual stresses.
Elasto-palstic stress analysis in transversely loaded composite laminated plates
n ABSTRACT Metal-matrix composites are new materials with superior properties. They provide high strength and stiffness, low density, resistance to corrosion, high creep and fatigue properties. These materials have gained a wide and popular range of use with several low cost manufacturing techniques developed in recent years. Elasto-plastic stress analysis plays an important role in metal-matrix composite researches. In this study, a stainless steel fiber reinforced aluminum metal-matrix laminated plate is investigated. The plate is simply supported and transversely loaded. Elastic, elasto-plastic and residual stresses are calculated in the symmetric and/or antisymmetric cross-ply and angle-ply laminated plate for small deformations by using finite elements method. The expansion of plastic zone is illustrated by using AcadR14. The plate is examined either without or with a circular hole. Iteration numbers are chosen as 100, 150 and 200 for the plate without a hole. Iteration numbers are also chosen as 200, 400 and 600 for the plate with a circular hole. Isoparametric quadrilateral element with nine nodes is selected for the elasto-plastic analysis. Metal-matrix composite laminated plate is manufactured by using moulds under 30 MPa pressure and heating up to 600 °C. The first-order shear deformation theory is used. A computer program in Fortran77 is developed to solve the problem. This program can be used to make similar analyses. The engineering constants are obtained by using strain gages in the tensile testing machine after production of the stainless steel-aluminum composite material.
Elastic-plastic stress analysis in multiple layered composite plates with holes
V ABSTRACT Advanced composite materials such as fiber reinforced plastic (FRP) and fiber reinforced metal (FRM) which have excellent mechanical properties have been recently developed. Before supplying them for commercial, we should perform various kinds of tests for characterizing their material properties. If a material has high capacity of carrying load, then it is called to have high mechanical properties. A good elasticity prevents the occurrence of sudden cracking deformations. It is very difficult to find materials which are both strong and elastic. What makes composite materials preferred over metalic materials is their having a much wider range of properties. Because of this, metals would not replace the composites where many requirements should be met. This study based on the three main stage. The first is that, manufacture of metal reinforced thermoplastic (Polyethylene F2-12) matrix composites and improve the product methods. The second, specimen preparation and finding the machine properties with the experiment. And the last, analyzing the result with finite element method by computer.