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Due to their high weight specific mechanical properties, fibre reinforced composite materials are increasingly utilized for high performance primary structures within aircraft wing and fuselage components. Yet, further exploitation is often limited due to rather high material and manufacturing costs including post-processing, concessions and rework. Additionally, very conservative engineering allowables are currently applied in order to account for uncertainties arising from manufacturing as well as operation phase. Further significant weight savings are expected for new structural components that are currently made from metals e.g. by reason of combined high thermal, mechanical or fire loading that cannot be bared by state of the art composites. In order to maintain the leadership of the European aeronautics, the European funded project SuCoHS is investigating potential weight and cost savings in expanding the use of composite materials in areas of demanding thermal conditions (temperature and fire). In particular, SuCoHS envisages new structural concepts with novel multi-material composites to provide high robustness against thermal, mechanical and fire loading. These developments also cater for high production rates, providing a cost competitive manufacturing process at minimum material and energy consumption, while reducing the requirement for visual inspection or rework. New solutions for structural health monitoring are considered within the structures to enable condition-based maintenance taking into account actual loading and structural conditions. The paper will provide insight into the project objectives as well as present the detailed concept and methodology for their achievement. Moreover, first technological developments of the project will be analysed.

The structural performance of thin shells is largely dictated by their curvature and the degree of lateral restraint at the shell edges. The present study is an attempt to theoretically investigate the influence of such factors on nonlinear thermo-mechanical response of shallow shells with single and double curvatures. For the mechanical loading, a transverse load is assumed and for the thermal loading, a through-depth thermal gradient is applied on the shallow shell. Two types of boundary conditions are considered for the shallow shell, both of which constrain transverse deflections of the shell but allow rotations parallel to the shell boundaries to be free. One of the boundary conditions permits lateral translation (laterally unrestrained) and the other one does not (laterally restrained). The fundamental nonlinear equations of shallow shells are derived based on the quasi-static conditions. The validity and reliability of the proposed approach is assessed by calculating several numerical examples for shallow shells under various mechanical and thermal loads. It is found that the proposed formulation, in particular, can adequately capture the nonlinear behaviour of laterally restrained shallow shells.

The current work is an attempt to reduce friction coefficient of the treated betelnut fibre reinforced polyester (T-BFRP) composites by aging them in twelve different solutions with different kinematic viscosities. The test will be performed on a pin on disc (POD) wear test rig using different applied loads (5–30 N), different sliding distances (0–6.72 km) at sliding speed of 2.8 m/s subjected to a smooth stainless steel counterface (AISI-304). Different orientations of the fibre mats such as anti-parallel (AP) and parallel (P) orientations subjected to the rotating counterface will be considered. The worn surfaces were examined through optical microscopy imaging and it was found that the aged specimens had significantly lower damages as compared to neat polyester (NP) and the unaged samples. Besides, P-O samples revealed lower friction coefficients as compared to AP-O, i.e., reduction was about 24.71%. Interestingly, aging solutions with lower kinematic viscosities revealed lower friction coefficients of the aged T-BFRP composites when compared to the ones aged in higher kinematic viscosities.

Titanium–tantalum based alloys can demonstrate a martensitic transformation well above 100 °C, which makes them attractive for shape memory applications at elevated temperatures. In addition, they provide for good workability and contain only reasonably priced constituents. The current study presents results from functional fatigue experiments on a binary Ti–25Ta high-temperature shape memory alloy. This material shows a martensitic transformation at about 350 °C along with a transformation strain of 2 pct at a bias stress of 100 MPa. The success of most of the envisaged applications will, however, hinge on the microstructural stability under thermomechanical loading. Thus, light and electron optical microscopy as well X-ray diffraction were used to uncover the mechanisms that dominate functional degradation in different temperature regimes. It is demonstrated the maximum test temperature is the key parameter that governs functional degradation in the thermomechanical fatigue tests. Specifically, ω-phase formation and local decomposition in Ti-rich and Ta-rich areas dominate when T max does not exceed ≈430 °C. As T max is increased, the detrimental phases start to dissolve and functional fatigue can be suppressed. However, when T max reaches ≈620 °C, structural fatigue sets in, and fatigue life is again deteriorated by oxygen-induced crack formation. Copyright © Materials Research Society 2017

This paper presents an integrated creep-fatigue (ICF) theory to describe the non-linear creep-fatigue interaction during thermo-mechanical loading. The ICF theory recognizes the damage evolution as a holistic process consisting of nucleation and propagation of surface or subsurface cracks in coalescence with internally distributed damage, leading to final fracture. In a polycrystalline material under combined cyclic and dwell loading, crack nucleation and propagation occurs by fatigue or oxidation mechanisms, whereas internally distributed damage often occurs in the form of grain boundary cavities or microcracks due to creep or dwell effects, particularly at high temperatures. Based on the above mechanism, a damage evolution equation is mathematically derived, and the generality of the above physical mechanisms warrants the applicability of the ICF theory over a wide range of stresses and temperatures. This paper uses Mar-M 509, a cobalt base superalloy, as an example to illustrate how the ICF theory describes creep and low cycle fatigue (LCF)., 13th International Conference on Fracture and Damage Mechanics, FDM 2014, September 23-25, 2014

International audience; This study aims to provide knowledge on the thermo-mechanical behaviour of heat exchanger piles, through a laboratory scale model. The model pile (20 mm in external diameter) was embedded in dry sand. The behaviour of the axially loaded pile under thermal cycles was investigated. After applying the axial load on the pile head, the pile's temperature was varied between 5 °C and 30 °C. Seven tests, corresponding to various axial loads ranging from 0 to 70 % of the pile estimated bearing capacity, were performed. The results on pile head displacement show that heating under low axial load induced heave and cooling induced settlement; the pile temperature-displacement curve was found to be reversible and compatible with the thermal expansion curve of the pile. However, at higher axial loads, irreversible settlement of the pile head was observed after a few thermal cycles. The axial load profile measured by the strain gauges evidenced that the pile head load was mainly transferred to the pile toe. Nevertheless, thermal cycles modified significantly the mobilised skin friction along the pile. The total pressure measured at various locations in the soil mass was also slightly influenced by the thermal cycles.

International audience; This work deals with the numerical prediction at different temperatures and under tension and simple shear of the Portevin-Le Chatelier (PLC) effect. The Estrin-Kubin-McCormick constitutive model was extended in a phenomenological way in order to take into account the influence of temperature and plastic anisotropy. The identification procedure used to calibrate the material parameters is detailed; it was split into 3 steps, considering separately elasticity and initial anisotropy, the mean stress level and then the serrations. A numerical analysis was conducted in order to examine the abilities of the model to reproduce most of the physical phenomena involved in the PLC effect. The numerical predictions were compared with experimental data obtained for an aluminum alloy at 4 temperatures, ranging from room temperature up to 200 degrees C, in terms of stress levels and bands kinematics, both in monotonic tension and simple shear. The dependence of the critical strain on strain rate and temperature, in tension and simple shear, was also investigated numerically. Finally, numerical predictions of the PLC effect during a loading up to a pre-strain followed by unloading then re-loading in the reverse direction was considered in simple shear and compared with experimental data. (C) 2016 Elsevier Ltd. All rights reserved.

Titanium-tantalum shape memory alloys (SMAs) are promising candidates for actuator applications at elevated temperatures. They may even succeed in substituting ternary nickel-titanium high temperature SMAs, which are either extremely expensive or difficult to form. However, titanium-tantalum alloys show rapid functional and structural degradation under cyclic thermo-mechanical loading. The current work reveals that degradation is not only governed by the evolution of the ω-phase. Dislocation processes and chemical decomposition of the matrix at grain boundaries also play a major role. DFG/NI1327/3-1 DFG/MA1175/34-1 DFG/EG101/22-1 DFG/FR2675/3-1

L'efficacité de pieux géothermiques (e.g. énergétiques) a été examinée et validée par de nombreuses études à partir de points de vue environnemental et énergétique jusqu'à présent. Néanmoins, la technologie des pieux géothermiques est encore peu connue et rarement appliquée dans la construction, notamment en France comparée à d'autres pays européens. La raison principale du manque d'attention peut être la connaissance limitée sur les impacts du chargement thermomécanique sur le comportement du pieu et celui du sol environnant. Cette thèse vise à étudier les aspects géotechniques des pieux géothermiques grâce aux modélisations physiques et numériques. Un modèle physique est développé afin de mieux connaitre l'interaction sol/pieu sous chargement thermomécanique. Le modèle est composé d'un pieu énergétique équipé des tubes d'échangeur de chaleur, installé dans un sol compacté. Le pieu a d'abord été installé dans un sable sec, puis dans une argile saturée ; il a ensuite été chargé mécaniquement et soumis à des cycles thermiques. L'effet de la charge mécanique, du nombre de cycles thermiques et du type de sol a été étudié. Les résultats montrent la génération de tassements irréversibles au cours des cycles thermiques, dont la quantité augmente avec l'augmentation de la charge en têtes du pieu. La pression totale dans le sol à proximité de la surface du pieu ne change pas par refroidissement et chauffage, tandis que la pression totale au-dessous du pieu augmente progressivement à mesure que les cycles thermiques poursuivent. Les expériences montrent aussi l'évolution des profils de la force axiale avec la température ; la force axiale dans le pieu augmente pendant le refroidissement et diminue pendant l'échauffement. Les comportements au cisaillement du sol (mêmes sols que ceux utilisés dans la première partie) ainsi que de l'interface sol/béton ont été évalués à différentes températures. Pour ce faire, un appareil de cisaillement conventionnel a été équipé d'un système de contrôle de température. Le sol (et l'interface sol/béton) a été soumis à une gamme de contraintes relativement faibles. La consolidation thermique a été effectuée selon un protocole particulier. Il a été observé que l'angle de frottement et la cohésion de matériaux utilisés ne changent pas sensiblement avec température. L'étude numérique a débuté par la simulation d'essais existants dans la littérature sur des pieux énergétiques en appliquant une méthode simplifiée via un code de calcul basé sur la méthode des éléments finis et assez répandu dans la profession. Le changement de la température est simulé en imposant au pieu des déformations volumétriques calculées à partir du coefficient de dilatation thermique du matériau. La méthode prédit correctement le comportement de certains pieux énergétiques à grande échelle en termes de contrainte axiale et de déplacement en tête du pieu. Les résultats mettent en évidence le rôle important joué par le changement de volume du pieu induit par les variations thermiques sur son comportement mécanique. Dans un second temps, un autre code de calcul offrant la possibilité d'inclure les effets thermique a été utilisé pour la modélisation des essais effectués auparavant sur le modèle physique. Ainsi, en comparant aux modélisations numériques précédemment expliquées, le changement de volume du sol induit par les variations de température est également pris en compte. Les résultats numériques et expérimentaux sont ainsi comparés. On en déduit que le modèle numérique est capable de prédire le comportement des pieux sous chargement purement mécanique. En outre, en simulant des essais thermomécaniques, une bonne estimation du transfert thermique dans le sol est obtenue. En ce qui concerne le comportement mécanique du pieu au cours de cycles thermiques, le modèle numérique prédit bien le tassement progressif du pieu. Cependant, en termes de répartition de la force axiale, on obtient des résultats contradictoires Energy pile efficiency has been tested and validated by numerous studies from environmental and energy-related points of view until now. Nevertheless, energy pile technology is still more or less unknown and rarely applied in construction, especially in France compared to other European countries. The chief reason for this lack of attention might be the limited knowledge of the impact of the coupled thermo-mechanical loading on the behaviour of the pile and that of the surrounding soil. This thesis aims to study the geotechnical aspects of energy piles through physical modelling and some numerical investigations. A physical model is developed in order to better identify the soil/pile interaction under thermo-mechanical loading. The model is made up of a small pile equiped with a heat exchanger loop embedded in compacted soil. The pile was once installed in dry sand and then in saturated clay; it was then loaded mechanically and was subjected to thermal cycles. The effect of mechanical load value, number of thermal cycles and soil type is studied. The results show the appearance of irreversible settlements during thermal cycles, whose quantity increases as the pile head load increases. Total pressure in the soil close to the pile surface does not change by cooling and heating, while total pressure below the pile increases gradually as thermal cycles proceed. This is in accordance with the permanent downward movement of the pile within thermal cycles. Experiments also show the evolution of axial force profiles with temperature, axial force in the pile increases by cooling and decreases by heating. In another part of the experimental work, we focused on the soil/pile interface. The shear behaviour of the soil (the same as the soils used above) and that of the soil/concrete interface was evaluated at different temperatures. To do this, a conventional shear apparatus was equipped with a temperature control system. Soil (and soil/concrete interface) was subjected to a rather low range of stress. Thermal consolidation was performed according to a special protocol. It was observed that the soil friction angle and cohesion do not change considerably relative to temperature. The numerical study was initiated by simulating existing tests in the literature on energy piles through a finite element code well-known to engineers, applying a simplified method. The thermal load was simulated by imposing volumetric strains calculated from the coefficient of thermal expansion of the material on the pile. The method successfully simulates the behaviour of some full-scale energy piles in terms of axial strain and pile head displacement. The results highlight the important role played by the pile thermal volume change on the mechanical behaviour of the energy pile under various thermo-mechanical loadings. In the second stage, another numerical code with the possibility of including temperature effects was used for modelling the tests formerly performed on the physical model. Thus, compared to the first numerical attempts, the soil thermal volume change is also taken into account. The numerical results were compared with the experimental ones obtained from physical modelling. It was deduced that the numerical model could simulate correctly the pile behaviour under purely mechanical loading. Also, simulating thermo-mechanical tests, a good estimation of heat conduction in the soil was achieved numerically. Regarding the mechanical behaviour of the pile under thermal cycles, the numerical model adequately predicts the gradual ratcheting of the pile as observed in the experiments. However in terms of axial force distribution in the pile, the results from numerical modelling are different from the physical one

In the last few years Technical University of Delft, under leadership of Prof.dr.ir. Leo Kouwenhoven, has developed several successful concepts for quantum devices that are suitable for quantum computing and quantum communication. From a quantum research point of view we are still in a very fundamental state, several practical issues already arise that are also important to a successful application and industrialization of quantum computing and communication. This paper will focus on these application issues. The quantum devices have the following challenges: (1) thousands to millions of the basic quantum manipulator, referred to as QuBit, must be connected to the outside (conventional electronic) world; (2) the circuits must be made stable and reproducible; (3) the excitation and control of the quantum states requires advanced low-power RF based control electronics; (4) they need to operate at very low (1K or less) to enable superconductivity that provides the right environment to induce the quantum states, as well as to minimize thermal energy interference of the quantum states. As the quantum device under investigation is built from nano-wires and thin metal films and operates at near zero [K], material properties will deviate typical bulk values at room temperature. Atomistic simulations are used to estimate these values and obtain insight into the mechanical behavior of the wire. A continuum model, that uses results of the atomistic simulations is used to obtain insight into the thermo-mechanical loading of the quantum devices due to cool down to the operating temperature of near zero Kelvin.

Given that most applications of shape memory alloys (SMA) are in the wire form, a reduced order model and analysis has been attempted in this paper. It takes into account the fact that the predominant actions are axial (bending inclusive) and torsional. A thermodynamic framework is first developed to simulate the behaviour of the SMA material under thermo-mechanical loading that is a combination of axial and shear stresses arising at a point in a wire due to axial and torsional loads applied to the wire. Since only a few variants relevant to axial-torsion are going to be active in transformation under this kind of loading, a reduced order model that tracks the evolution of four martensite variants and an austenite variant is proposed. It is shown through simulations that these five model parameters amply form a minimal set of model parameters sufficient for simulating response under tension-torsion loading excursions. The model is further applied to the structural member, in this case, a wire of circular cross-section subject to a twist and an axial extension and the capability of the model to simulate the kind of response expected in wires. Incorporation of this model into a large deformation space frame nonlinear analysis will help in the design and analysis of several applications where SMA wire forms are used. � 2014 IOP Publishing Ltd.

The long term durability of CFRP strengthened steel structures is a key parameter for their safe use and effective design. Strengthened members can be subjected to different environmental conditions and loading scenarios during their service life, the effect of which on the failure mechanism of the strengthened members require fundamental investigations. This research presents experimental and theoretical investigations on the effects of freeze-thaw cycling and wet thermo-mechanical loading on the bond strength and failure mode of steel-CFRP adhesive joints. The influence of these conditions on the mechanical properties of pure epoxy is also investigated to give insight into the structural behaviour and also provide data for the theoretical model. The results show that the freeze-thaw cycling decreases the bond strength of the joint by about 28% and leads to variations in the failure mode. A reduction in the initial elastic modulus of the pure epoxy was also observed. The results of the wet thermo-cyclic exposure combined with sustained loading show that these conditions have little impact on the bonding strength when applied separately. However, when applied simultaneously, the mechanical properties of the epoxy and the bond strength of the joints are significantly reduced with failure observed at less than 30% of the static strength and at the temperature range well below the glass transition temperature of the adhesive. A simple shear stress-slip model is developed to analyse single-lap joints, in which the effects of freeze-thaw and thermal cycling are introduced in terms of reduced elastic modulus of the adhesive. The predicted failure load correlates well with the experimental data. A more accurate high order model is also developed that is combined with fracture mechanics and can account for the shear deformability of the adhesive layer and considers normal interfacial stresses. A new methodology to evaluate the effects of freeze-thaw cycling is proposed, which considers the effect of moisture swelling, thermal expansion and change in material properties. Finally, parametric studies are conducted and the results are presented in terms of bond strength, interfacial stresses and deformations.

In the last few years Technical University of Delft, under leadership of Prof.dr.ir. Leo Kouwenhoven, has developed several successful concepts for quantum devices that are suitable for quantum computing and quantum communication. From a quantum research point of view we are still in a very fundamental state, several practical issues already arise that are also important to a successful application and industrialization of quantum computing and communication. This paper will focus on these application issues. The quantum devices have the following challenges: (1) thousands to millions of the basic quantum manipulator, referred to as QuBit, must be connected to the outside (conventional electronic) world; (2) the circuits must be made stable and reproducible; (3) the excitation and control of the quantum states requires advanced low-power RF based control electronics; (4) they need to operate at very low (1K or less) to enable superconductivity that provides the right environment to induce the quantum states, as well as to minimize thermal energy interference of the quantum states. As the quantum device under investigation is built from nano-wires and thin metal films and operates at near zero [K], material properties will deviate typical bulk values at room temperature. Atomistic simulations are used to estimate these values and obtain insight into the mechanical behavior of the wire. A continuum model, that uses results of the atomistic simulations is used to obtain insight into the thermo-mechanical loading of the quantum devices due to cool down to the operating temperature of near zero Kelvin.

Thin layers of dissimilar materials are used in most microelectronic components in order to achieve special functional requirements. Generally, the interface between two adjacent materials forms a weak link, not only because of the relatively low delamination strength, but also because of the existing mismatch in thermo-mechanical properties, such as Young’s modulus, coefficient of thermal expansion, hygro-swelling, and vapor pressure induced expansion. Residual stresses from the production processes and initial strains due to the changing thermal and humidity conditions together with acting mechanical loading form the crack driving factors for interface delamination. Failure of interface induces decreased reliability of microelectronic components. Nowadays, interfacial delamination forms one of the key reliability issues in the microelectronic industry and therefore is getting more and more attention. The analysis of a laminate structure with a crack along the interface is central to the characterization of the delamination toughness. The delamination toughness is highly dependent to temperature, moisture and mode mixity. In recent years, several studies were directed at the determination of the delamination behavior of Cu-EMC interfaces. In the event that moisture sensitivity was included in these studies, the temperature had to be limited to below 100oC. This limitation reduces the applicability of the toughness data obtained in a number of reliability studies of micro-electronic components. This is due to the fact that, in preconditioned (humid) micro-electronic components the interface delamination often occurs above this temperature limit. In many cases the damage is initiated during heating up in subsequent production steps, where temperatures can reach far above 100oC. Therefore the present research focuses on interface delamination measurements, especially interested in harsh environment (humidity combined with temperatures above the 100oC limit). In this thesis the thermal-mechanical properties of epoxy molding compounds in dry conditions are first investigated. The coefficient of thermal expansion and bulk modulus were measured via a dilatometer (PVT apparatus). DMA experiments in relaxation mode as well as in multi frequency mode were employed for obtaining the viscoelastic master curve and corresponding shift factors. Secondly, the thermo-mechanical properties of EMC during cure were studied. The volumetric contraction of the material during the curing period was measured via a PVT test. Furthermore the increasing shear modulus of the EMC because of the progressing cure was established through DMA experiments. For the dry state, the previous two-material characterization steps are sufficient to be able to interpret the measurement results of delamination tests via FEM simulation. For the humid state with T> 100 °C, in the delamination measurements the effect of (trapped) steam at the interface should be compensated by performing the measurements in a pressure chamber. Therefore, in a third step a pressure vessel surrounding the delamination test setup is designed and built. For the sake of simplicity the humid delamination measurements with T> 100 °C were only performed under full steam pressure (=relative humidity is 100%). The functionality of the setup has been verified by the measurement of the viscoelastic creep compliance of an EMC in dry state and to compare this with the result from measurements obtained from a commercially available measurement instrument. In order to be able to perform delamination measurements a mixed-mode bending setup is installed in the pressure vessel. Interfacial delamination measurements for a EMC-Cu lead frame interface (as obtained from a real production process) are subsequently performed for dry conditions as well as under pressurized steam conditions(= relative humidity 100%). A (I / II) mixed mode mechanical load is applied to the test sample, in which the initial stress state due to the manufacturing and the steam pressure (relative humidity 100%) is already present, in order to initiate and propagate the delamination. In conclusion: This dissertation shows that the temperature, the mix mode and the humidity under these conditions (T> 100 °C and 100% relative humidity) results in a significant effect on the delamination properties of interfaces. As far as known to the author, here for the first time a good insight on the impact of this harsh environment on the delamination properties is presented.

TITEL UND INHALTSVERZEICHNIS 1\. EINLEITUNG 2\. EIGENE ARBEITEN 3\. RELEVANTE ORIGINALARBEITEN 4\. DISKUSSION 5\. ZUSAMMENFASSUNG 7\. LITERATUR, Glasfaserverstärkte Komposit-Aufbaustifte (GFP) dienen der Retentionssteigerung eines plastischen Aufbaumaterials für die Indikation der postendodontischen Versorgung. Sie gelten als nicht-metallische und - aufgrund ihrer zahnähnlichen Einfärbung - ästhetische Alternative zu metallischen Aufbaustiften. Als wesentlicher Vorteil wird der dem Dentin ähnliche E-Modul von GFP postuliert. Die in der Habilitationsschrift vorgestellten Ergebnisse der In-vitro-Untersuchungen zeigen, dass die thermomechanische Wechsellast (Kausimulation) gefolgt von einer linearen Belastung bis zum Versagen für die Untersuchungen zur Aufbaustiftproblematik am geeignetsten ist. Ferner wurde die verbliebene Wurzelwandstärke auf Niveau des Kanaleinganges als eine limitierende Größe in der postendodontischen Versorgung mit GFP herausgestellt. Der Fassreifeneffekt (engl. ferrule effect) trägt wesentlich zur Stabilisierung des postendodontischen Komplexes bei. Jedoch nur die Kombination von Aufbaustift, gleichgültig, ob flexibler glasfaserverstärkter Komposit oder rigides Titan, mit dem Fassreifen steigert synergetisch die Belastbarkeit einer postendodontischen Restauration. Da auch GFP nicht wiederversorgbare Frakturmuster verursachen, kann die strikte Forderung nach der Verwendung von Aufbaustiften mit dentinähnlichem E-Modul auf dieser Basis nicht unterstützt werden. Die Versorgung von Frontzähnen, Zähnen ohne Approximalkontakt und die Einzelkronenrestauration wurden in einer prospektiven klinischen Observationsstudie als Risikofaktoren identifiziert. Adhäsiv zementierte Titanstifte und GFP zeigten im Rahmen einer randomisierten, kontrollierten klinischen Studie im Parallelgruppendesign die gleiche Erfolgswahrscheinlichkeit, wobei nach einer Nachuntersuchungszeit von bis zu drei Jahren keine Misserfolge auftraten., Glass fibre reinforced composite posts (GFP) are used for postendodontic restorations to support the composite resins core build-up material. They are a non-metallic and - due to its tooth colour - aesthetic alternative to metal posts. The more dentin-like Young s Modulus compared to metallic posts is seen as its major advantage. The presented in-vitro data show, that thermo- mechanical loading (chewing simulation) and additional linear loading until failure is appropriate for in vitro testing of post-and-core restorations. It was found that the remaining wall thickness of the root on the level of the root canal entrance is the limiting factor of the postendodontic restoration with GFP. Furthermore, it was shown that the ferrule effect is the key factor to stabilise the postendodontic complex. However, only the combination of post and ferrule, irrespective of the post material used, improves the load capability of the restored tooth. It was found that also the use of GFP as described for metal posts - may lead to non-restorable failures. Thus, in regard to fracture patterns observed there is no advantage of GFP compared to metal posts. In an observational clinical study the restoration of front teeth, the absence of proximal contact points and placement of single crown restorations were found to be risk factors of GFP-restored teeth. Adhesively placed titanium and GF-posts did show the same success rate in a randomised controlled clinical trial in a parallel group design. No failure occurred after a time of observation of about three years.

A coupled thermal and structural 3d quasi stationary Finite Element (FEM) analysis of a typical rocket combustion chamber wall during a full cycle including pre cooling, hot run, post cooling and relaxation is presented. The results of this 3d analysis are compared with the results of 2d plane strain and 2d generalized plane strain analyses. Finally, a post-processing method is applied in order to estimate the combustion chamber life time. This life time estimation method takes into account the standard Low Cycle Fatigue part as well as additional parts – accounting for the quasi static (or ratcheting) fatigue and the thermal degradation of the chamber wall material.

A Finite Element analysis of carbon nanotube (CNT) reinforced Epoxy based composite subjected to thermo-mechanical loading is presented in this paper. A coupled field analysis of a hexagonal RVE with long and short CNT embedded in an epoxy polymer matrix is carried out to analyze the effect of CNT reinforcement on the thermo-mechanical properties of the epoxy polymer. The analysis shows that long CNT's prove to be better reinforcement than short CNT's for the nano composites subjected to thermo-mechanical loading

Energy piles, due to their dual roles, are exposed to temperature change throughout their life time, which may cause axial displacements, additional axial stresses and changes in the shaft resistance along their lengths. The extent of these effects highly depends on the level of restrictions along the energy piles, from the surrounding soil, as well as from the superstructure. A full-scale in-situ test has been performed on three energy piles, with the purpose of investigating their thermo-mechanical behaviour with respect to the corresponding end-restraining conditions. Thermal loads with maximum temperature of 45 degrees C and minimum of 8 degrees C were applied to the test piles for a 6-week period along with conventional mechanical load tests. Two of the test piles were designed to have base resistance from the very dense sand layer while the shorter pile was tipped into a stiff clay layer with the purpose of representing different end-restraining conditions. Moreover, the thermal loads were applied to the longer piles with and without the presence of mechanical load at the head. In this paper, the full-scale in-situ test setup is presented, along with the test results of the three test piles giving emphasis to the restraining effects of the mechanical load at the head and the base resistance from underlying soil layers. It is concluded from the results that the distribution of thermally induced axial stresses and the mobilization of shaft resistance during heating and cooling episodes are highly dependent on the location of the dominant restriction. Moreover, the end-restraining effects fade away at depths farther from the dominant restriction, leading to the degree of freedom of test piles with diverse end-restraining conditions to converge. (C) 2018 Elsevier Ltd. All rights reserved.