Ayşe Öndürücü

Thermal Residual Stresses in Simply Supported Thermoplastic Laminated Plates under a Parabolic Temperature Distribution

In the present study, a thermal elastic-plastic stress analysis is carried out on simply supported symmetric cross-ply [0/90]2 and angle-ply [30/30]2, [45/45]2, and [60/60]2 thermoplastic laminated plates. The temperature changes parabolically along the thickness of the plates. It is T0 and T0 at the upper and lower surfaces, respectively. The composite material is assumed to be linear strain hardening. An analytical solution is performed for satisfying the thermal elastic-plastic stress-strain relationship and boundary conditions for small plastic deformations. The Tsai-Hill theory is used as a yield criterion. The elastic-plastic solution is carried out for small plastic deformations. The residual stress distributions along the thickness of the plates are obtained.

Thermal Elastic–Plastic Stress Analysis of Aluminum Metal–Matrix Composite Laminated Plates Under a Parabollically Temperature Distribution:

In this study, a thermal elastic–plastic stress analysis is carried out on steel-fiberreinforced aluminum metal–matrix composite laminated plates fixed at all edges. Temperature is chosen to vary parabollically. It is zero and T0 on the middle axis and at the upper–lower surfaces, respectively. The solution is executed for symmetric cross-ply (0° /90°)2 and angle-ply (30° / -30°)2, (45° / -45°)2, (60° / -60°)2 laminated plates. The elastic–plastic solution is carried out for small plastic deformations. The Tsai–Hill Theory is used as a yield criterion. Residual stress distributions along the thickness of the plates are obtained. All the residual stress components are in static balance with respect to middle plane of the laminates since they are symmetric in opposite signs.

An Elastic-Plastic Stress Analysis of Symmetric Aluminum Metal-Matrix Composite Laminated Plates Under Thermal Loads

In this study, a thermal elastic-plastic stress analysis is carried out on symmetric cross-ply (0°/90°)2 and angle-ply (30°/30°)2, (45°/45°)2, (60°/60°)2 aluminum metal-matrix composite laminated plates. Temperature changes parabolically from T0 up to T0 along the thickness. It is zero on the middle axis. The composite material is assumed to be linear strain hardening. The Tsai-Hill Theory is used as a yield criterion. The elastic-plastic solution is carried out for small plastic deformations. The distributions residual stress components of σ x and σ y are illustrated along the thickness of the laminated plates. All the residual stress moments are in static balance with respect to middle plane of the laminates since they are symmetric in opposite signs.

An Elasto-Plastic Analysis of Thermoplastic Composite Cantilever Beam Loaded by a Single Force at Its Free End

In the present study, an elastic–plastic stress analysis is carried out on a high-density thermoplastic-based composite cantilever beam loaded by a single force at its free end. An analytical solution is performed for satisfying both the governing differential equation in the plane stress case and boundary conditions for small plastic deformations. The solution is carried out under the assumption of the Bernoulli–Navier hypotheses. The composite material is assumed to be strain-hardening. The Tsai–Hill theory is used as a yield criterion. The residual stress component of x are determined for 0, 30, 45, 60 and 90 orientation angles. It is found that the intensity of the residual stress is maximum at the upper and lower surfaces of the beam. The horizontal displacement component of u is greater than the vertical displacement component of v.

Hibrit Kompozit Kirişlerin Yanal Burkulma Davranışlarına Soğuk Ortamın Etkisi

Bu calismada, hibrit kompozit kirislerin yanal burkulma davranislari uzerine soguk ortamin ve farkli fiber kombinasyonlarinin etkileri deneysel olarak arastirilmistir. Yanal burkulma deneyleri icin, karbon, E-cam ve aramid fiberlerin farkli kombinasyonlari ve matris olarak da Araldite LY1564/Aradur 3486 recine sistemi kullanilarak 12 tabakali hibrit kompozit plakalar uretilmistir. Hibrit kompozit numuneler 90 gun oda kosullari, 90 gun sogutucu ve 150 gun sogutucuda bekletildikten sonra yanal burkulma deneyine tabi tutulmuslardir. Deneyler sonucunda elde edilen veriler dogrultusunda tabakali hibrit kompozit kirislerin yanal burkulma davranislari incelenmistir. En yuksek kritik yanal burkulma yuku [(30/-60) 3 ] s istifleme dizilimine sahip CAG 30 numunelerinde, en dusuk kritik yanal burkulma yuku ise [(0/90) 3 ] s istifleme dizilimine sahip GAC numunelerinde meydana gelmistir. Calisma sonucunda, soguk ortamda bekletilen numunelerin kritik yanal burkulma yuklerinin oda kosullarinda bekletilen numunelerin kritik yanal burkulma yuklerine gore arttigi belirlenmistir.

Effect of preload moment on the strength of mechanically fastened joints in woven glass-epoxy prepregs

Abstract This study presents the effects of geometric parameters of mechanically fastened joints on their ultimate bearing strength, net ultimate tensile strength and ultimate shear strength under various preloads. In the experiments, two different geometric parameters were considered: edge distance-to-hole diameter ratio (E/D) and plate width-to-hole diameter ratio (W/D), and magnitudes of preload moments applied on the specimens at about 0, 2, 4 and 6 Nm. Damage to the specimens subjected to different moments of the same geometric dimensions was examined by using a scanning electron microscope (SEM). The experimental test results showed that the ultimate bearing strengths, net ultimate tensile strengths and ultimate shear strengths are strictly affected by the geometrical parameters and the magnitude of the preload moment.

Effect of seawater on the buckling behavior of hybrid composite plates

This paper addresses the effects of different stacking sequences and seawater on the buckling behavior of hybrid composite plates. For the buckling tests, 12-layered hybrid composite plates were produced using different combinations of carbon, E-glass and aramid fibers, with an epoxy resin system as the matrix (Araldite LY1564/Aradur 3486). The hybrid composite plates were designed at the symmetric orientation angles of [(0/90)3]s, [(30/−60)3]s, [(45/−45)3]s and an anti-symmetric orientation angle of [(0/90)3]2. The hybrid composite samples were divided into groups and were subjected to buckling tests after being kept in different settings for varying periods of time (room temperature for 90 days, Black Sea water for 90 days, Mediterranean Sea water for 90 days, Mediterranean Sea water for 150 days). In light of the data obtained from the tests, the buckling behaviors of the layered hybrid composite plates were examined. The highest critical buckling load occurred in the carbon/aramid/glass (CAG) hybrid samples with the stacking sequence of [(0/90)3]s, whereas the lowest critical buckling load occurred in the carbon/aramid/glass (CAG45) hybrid samples with the stacking sequence of [(45/−45)3]s. It was observed that the critical buckling loads of the samples immersed in seawater decreased when compared to the critical buckling loads of the samples kept at room temperature. It was also found that the critical buckling loads of the hybrid samples immersed in the Mediterranean Sea water, which has high salinity, were lower than the critical buckling loads of the hybrid samples immersed in the Black Sea water, which has lower salinity.

ANN evaluation of bearing strength on pin loaded composite plates in different environmental conditions

Abstract The main aim of this study is to estimate the bearing strength on pin loaded composite plates using test data of different ambient conditions depending on time. Artificial neural network (ANN) tool is used for prediction purpose. Artificial neural network program is developed by MATLAB software. The composite plates were divided into nine groups, each one contains 60 specimens. These groups were kept in different environment conditions. To obtain the optimum geometrical dimensions of specimens, the distance from hole axis to the side of the test sample of the pin diameter ratio (E/D) and the sample width to pin diameter ratio (W/D) were changed systematically in the experimental samples. Data from fatigue test results obtained from the multi-layered, feedforward and backpropagation algorithm were used to train the artificial neural network model. In modeling of artificial neural network, the test conditions, the test periods, the day intervals, the distance from hole axis to the side of test sample of the pin diameter ratio (E/D) and the sample width to pin diameter ratio (W/D) were used as input parameters and the bearing strength data was used as output parameter. The values obtained from the artificial neural network training and testing were evaluated by applying statistical analyses that are widely used in ANN models. It is widely known that difficult experimental studies and complexity of the analytical expression could be solved by ANN models as it was seen in many studies. This study has also shown that artificial neural network is a convenient method for predicting the bearing strength on pin loaded composite plates.

An Elasto-Plastic Stress Analysis of Simply Supported Thermoplastic Composite Beams under a Transverse Linearly Distributed Load

An analytical elasto-plastic stress analysis is carried out on thermoplastic composite beams supported from two ends under transverse linearly distributed load. The composite beams consist of woven steel fiber and thermoplastic matrix. The material is assumed to be perfectly plastic for the elasto-plastic solution. The expansion of the plastic region and the residual stress component of σχ are determined for 0°, 15°, 30° and 45° orientation angles. The yielding begins at the upper and lower surfaces of the beam at the same distances from the ends. The intensity of residual stress component of σχ is maximum at the upper and lower surfaces but residual stress component of τχ>. is maximum on the χ axis of the beam. The strength of the beam is increased by residual stresses.

An Elasto-plastic Stress Analysis of Aluminum Metal-Matrix Composite Beam Subjected to Transverse Linearly Distributed Load

An analytical elasto-plastic stress analysis is carried out on metal-matrix composite beams supported from two ends under transverse linearly distributed load. The composite beam consists of stainless steel fiber and aluminum matrix. The material is assumed to be perfectly plastic for the elasto-plastic solution. The expansion of the plastic region and the residual stress component of x and τxy are determined for 0, 30, 45, 60, and 90 orientation angles. The yielding begins at the upper and lower surfaces of the beam at the same distances from the ends. The intensity of residual stress component of x is maximum at the upper and lower surfaces but residual stress component of τxy is maximum on the x axis of the beam. The strength of the beam is increased by residual stresses.