Anastasios P. Vassilopoulos

Anastasios P. Vassilopoulos
École Polytechnique Fédérale de Lausanne | EPFL

About

173
Publications
13,083
Reads
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3,127
Citations
Citations since 2016
60 Research Items
2082 Citations
20162017201820192020202120220100200300400
20162017201820192020202120220100200300400
20162017201820192020202120220100200300400
20162017201820192020202120220100200300400
Introduction
Anastasios P. Vassilopoulos currently works at École Polytechnique Fédérale de Lausanne. Anastasios does research in Structural Engineering, Mechanical Engineering and Materials Engineering.

Publications

Publications (173)
Article
Hybrid adhesives can be developed using commercially available adhesive materials and customized to the required loading conditions. In this paper, SPABOND™ 820HTA (non-toughened) and SPABOND™ 840HTA (toughened) adhesives were hybridized with two strategies and fabricated by machine and manual mixing methods. The manufacturing and hybridization eff...
Article
Full-text available
A probabilistic model for estimating the fatigue life of composite laminates based on the mean value and standard deviation of the fatigue life is introduced here for predicting the distribution of fatigue life at any stress level for a constant stress ratio. The proposed model is validated with experimental data for several composite materials, an...
Article
This paper presents the results of an experimental campaign designed specifically to investigate unexpected and unwanted failures observed during the quasi-static and fatigue tensile loading of structural adhesives. Simple finite element models were also developed to support the arguments drawn from the experimental investigations. Particular param...
Article
The load-bearing performance of sandwich bridge decks comprising a balsa core and fiber-reinforced polymer composite face sheets exposed to fire is a main concern regarding the application of these deck systems. In order to obtain the thermal responses of the balsa core exposed to fire, the temperature-dependent values of thermal conductivity and s...
Chapter
The lack of ductility is a major drawback of fibre reinforced polymer (FRP) materials. As it is known, these materials are stiff and strong, but brittle with little or no warning before final failure. In the last decades, some solutions have been proposed with the aim of having FRP materials with pseudo-ductile behaviour. For instance, the use of u...
Article
Full-text available
The development of new adhesives has allowed to expand the application of bonding into the most diverse industrial fields. This review article presents the commonly used experimental methods for the investigation of mechanical performance of adhesively bonded joints in the aerospace, wind energy, automotive and civil engineering sectors. In these s...
Article
Hybrid composites become popular and are today used in a large number of contemporary structural applications. When compared to non-hybrid composites, hybridization offers additional benefits since the mixing of cheaper, low-quality fibers, with more expensive fibers of higher quality can improve the properties of a composite without significantly...
Article
A 3D printed bio-composite removable connection system for bamboo space structures is introduced in this paper. The system consists of a removable clipping connection for raw bamboo structures, adapted to the European market. The use of parametric design and 3D printing enables to have both design and production processes adapted to the non-uniform...
Article
The two-dimensional (2D) delamination growth in fiber-reinforced polymer (FRP) laminates with in-plane isotropy under Mode I loading condition was numerically investigated using finite element analyses. Two sizes of plate models were developed, focusing on different fracture stages. Cohesive elements were employed to simulate the fracture behavior...
Article
Full-text available
This work investigates the quasi-static, low-cycle and fatigue behavior of hybrid glass/ultra-high modulus carbon (GC) and low modulus/ /high modulus carbon (CC) fiber composites. These pseudo-ductile unidirectional interlayer hybrids are a new type of composites whose potential is not yet fully understood, particularly under cyclic/fatigue loading...
Article
Balsa wood is an appropriate core material for structural sandwich applications due to its high strength- and stiffness-to-weight ratios. However, the mechanical properties vary considerably owing to the inherent scattering of natural wood materials. One approach to reduce this scatter and tailor the mechanical properties according to specific appl...
Article
Fatigue of structural adhesives has been investigated through joints and a little number of works investigate bulk adhesive behaviour itself. Aerospace and automotive engineering focuses more on joint configuration studies, which are correlated with practical applications. Previous works showed that for thin adhesive joints, material properties mea...
Article
Full-text available
The aim of this work is the investigation of mesoscale/local variability in mechanical properties of clear timber in the radial direction. Clear Norway spruce wood, Picea abies, was used for cutting specimens of different lengths with a small cross-sectional area of 4 × 4 mm², in the radial direction of timber boards, and tested under tensile loadi...
Article
Full-text available
This paper investigates the effects of degassing, curing and post-curing conditions on the tensile quasi-static and fatigue behavior of a cold-curing structural epoxy adhesive. Quasi-static experiments performed at standardized and high displacement rates similar to those imposed to the material under fatigue loading, in order to derive comparable...
Conference Paper
Adaptive kinetic façades are systems capable of modifying their shape to optimize their behavior regarding real time outdoor and indoor conditions. They are typically evaluated based on quantifiable physical parameters such as illuminance levels, with little attention-for lack of evaluation criteria-given to subjective appreciation of the façade an...
Article
An experimental investigation of the two-dimensional (2D) debonding behavior of GFRP/balsa sandwich panels with embedded circular disbonds at the face sheet/core interface subjected to out-of-plane fatigue loads was conducted. The constant amplitude fatigue experiments were performed under load control and different R-ratios. Two face sheet configu...
Article
A general constitutive equation was established using the theory of viscoelasticity in order to consider the interaction of the time- and cyclic-dependent mechanical properties of laminated composites. This equation was solved for two specific loading patterns, (1) stress unloading to zero stress level (recovery solution), and (2) load control sinu...
Article
The effect of the stress ratio (R = σ min /σ max ) on the fatigue behavior of (±45) 2S angle-ply glass/epoxy composite laminates was investigated by comparing their mechanical, thermal, and optical properties under the stress ratio of 0.5 with previous fatigue results obtained under the stress ratio of 0.1. When the stress ratio was increased from...
Article
Full-text available
Lightning strikes pose a serious natural threat to carbon fiber-reinforced polymers (CFRPs). Knowledge of the electrical current distribution is essential for modeling the interaction between CFRP with lightning. In most applications, the anisotropy of CFRP makes the electrical current tend to concentrate on the surface, having significant influenc...
Article
A new numerically-based method suitable for determining the total strain energy release rate (SERR) involved in two-dimensional (2D) Mode I-dominated delamination under opening loads in FRP laminates is presented. The method is based on the mutual dependence of the load vs opening displacement curves slope exhibited after the full development of th...
Article
Angle-ply (±45) 2S glass/epoxy composite specimens have been subjected to pure creep and tension-tension constant amplitude fatigue loading interrupted at σ max by creep intervals lasting for 2 or 48 h in order to examine the effects of creep loading on the fatigue response and vice versa. The specimens’ behavior and damage status were continuously...
Article
The two-dimensional (2D) debonding behavior of GFRP/balsa sandwich panels presenting embedded circular disbonds at the face sheet/core interface was experimentally investigated. The bottom of the panels was fixed and out-of-plane quasi-static tensile loads were applied to open the crack. Two different face sheet configurations were studied. The fir...
Article
The 2D delamination behavior of composite laminates under quasi-static out-of-plane opening loading has been experimentally investigated. A circular embedded pre-crack was introduced in the center and at the midplane of the laminates. To investigate the effect of the fiber architecture on the fracture behavior, six different types of fabrics were s...
Article
In this study, the temperature effect on the static and tension–tension fatigue behavior of basalt fiber‐reinforced epoxy polymer (BFRP) composites is investigated. The S–N curves, energy dissipation, stiffness degradation, and displacement increment with lifetime under temperatures of −20, 0, 20, 40, and 60°C were derived to evaluate the BFRP fati...
Article
In the field of timber load-bearing structures, adhesive bonding is a promising joining technique that may increase the structural stiffness and capacity of timber joints and structures. The use of ductile adhesives may furthermore allow designing ductile joints, which can compensate for the material ductility that timber lacks. To demonstrate the...
Article
Full-text available
The tension–tension fatigue behavior and damage mechanism of basalt fiber-reinforced epoxy polymer (BFRP) composites at different stress ratios are studied in this paper. The fatigue experiments were performed under stress ratios, R = σmin/σmax of 0.1 and 0.5, while the lifetime and the stiffness degradation were monitored and analyzed to investiga...
Article
The compressive kinking behavior of non-slender unidirectional glass fiber-reinforced polymer (GFRP) specimens has been analyzed by finite element (FE) models. The experimentally observed imperfections, including the initial fiber waviness throughout the entire specimen volume and the scattered resin/interface defects, were taken into account in th...
Article
Full-text available
The two-dimensional (2D) delamination behavior of composite laminates under quasi-static out-of-plane opening loads has been experimentally investigated. A novel design and experimental set-up for fiber-reinforced polymer (FRP) laminated plates with a circular embedded pre-crack was developed. Increasing load-displacement curves were obtained due t...
Article
The effect of load interruptions on the tension-tension fatigue behavior of angle-ply (±45)2S glass/epoxy composite laminates was investigated. The cyclic loading was interrupted for two hours at regular cycle intervals, corresponding to 20% of the fatigue life under continuous loading at the same maximum cyclic stress level. Fatigue stiffness was...
Article
The tensile behavior of non-laminated and laminated CFRP straps composed of up to 100 layers was numerically and analytically investigated. The failure mode in non-laminated straps changed at 20–30 layers from brittle and sudden rupture of the outermost layer to progressive rupture starting from the innermost layer, due to the different non-uniform...
Article
A numerical investigation was carried out in order to simulate experimental results previously obtained concerning two-dimensional (2D) in-plane crack propagation in laminated glass fiber-reinforced polymer (GFRP) plates. The laminated plates were designed with an embedded circular pre-crack and subjected to quasi-static out-of-plane loads. In orde...
Article
The fatigue behavior of (±45)2S angle-ply glass/epoxy composite laminates was investigated. Rectangular specimens were subjected to constant amplitude fatigue loading at different stress levels, with stress ratio 0.1 until failure. A video-extensometer and an infrared thermal camera were employed respectively to measure the evolution of strain and...
Article
An investigation of the load-transfer mechanism in carbon fiber-reinforced polymer (CFRP) ground anchors with multi-strap ends was conducted based on experimental and numerical studies of one- and two-strap anchors. Differences in the strap geometry, i.e. different curvature distributions and transitions from the rod to the strap cross section, and...
Article
An evaluation of cement- and resin-based grout materials for applications in carbon fiber-reinforced polymer (CFRP) ground anchor heads composed of high-strength grout and a CFRP strap was conducted. Uniaxial compression experiments were performed on cylinder specimens. Appropriate loading-control methods and boundary conditions were determined in...
Conference Paper
The effect of physical aging and continuation of curing on the physical and mechanical properties of a commercial cold-curing structural epoxy adhesive used in bridge construction has been investigated during the first year. Since adhesive bridge joints are sealed, only dry conditions were taken into account. Predominant physical aging in the earli...
Conference Paper
The physical and mechanical properties of a cold-curing structural epoxy adhesive were investigated if exposed to a wet bridge environment. A significant decrease of the glass transition temperature, elastic tensile modulus and tensile strength was observed which could be attributed to plasticization. A retention of 70% of E-modulus and strength at...
Article
The physical and mechanical properties of a cold-curing structural epoxy adhesive, exposed to a wet bridge environment, were investigated. A significant decrease of the glass transition temperature, tensile E-modulus and tensile strength was observed which could be attributed to plasticization. The retention of 70% of the E-modulus and strength at...
Article
Full-text available
A quasi-static progressive damage model for prediction of the fracture behaviour and strength of adhesively bonded fibre-reinforced polymer joints is introduced in this paper. The model is based on the development of a mixed-mode failure criterion as a function of a master R-curve derived from the experimental results obtained from standard fractur...
Article
The ductility and time-dependent recovery of a ductile acrylic adhesive were investigated in this work. The quasi-static true tensile and compressive strain behaviors were examined at different strain rates, taking large deformations into account. Yield stress, elastic modulus, and failure strain exhibited a logarithmic dependency on increasing str...
Article
The effect of physical aging and continuation of curing on the physical and mechanical properties of a commercial cold-curing structural epoxy adhesive used in bridge construction has been investigated during the first year. Since adhesive bridge joints are sealed, only dry conditions were taken into account. Predominant physical aging in the earli...
Article
This paper presents the results of an experimental program designed to study the effects of aging and a wet environment on the fatigue behavior of epoxy resins used in bridge applications. Specimens were manufactured, cured, and treated, before the experiments, under a variety of conditions, in room and in water environments, in order to simulate t...
Article
The effects of the loading type, i.e. tension or compression, and displacement rate on the Poisson ratio of a non-linear viscoelastic ductile structural adhesive have been investigated using digital image correlation-based strain fields. The results showed that the Poisson ratio should be based on true strains to take geometry changes into account....
Article
The use of sensitive electronics in avionics and wind generation systems, as well as the introduction of lower-conductivity composite materials make it important to ensure adequate lightning testing of airplanes and wind turbines. Evidence exists suggesting that standardized testing lightning waveforms produce damages that differ from those observe...
Article
Full-text available
The partitioning of the total strain energy release rate, Gtot, into the Mode I, GI, and Mode II, GII, components is challenging, especially in asymmetric cracks. Although many researchers have studied the fracture behavior of composite materials under mixed-mode loading using symmetric and/or asymmetric mixed-mode bending (MMB) specimens, few stud...
Article
Pull-out experiments were performed on three carbon fiber-reinforced polymer (CFRP) ground anchors simulating their applications in different rock types which provided different confinement levels. The CFRP tendons comprised, on the ground side, a prefabricated conical anchor body of high-strength grout in which two CFRP straps were embedded. The a...
Article
Pull-out experiments were performed on four carbon fiber-reinforced polymer (CFRP) ground anchors simulating their applications in rock and soil. The CFRP tendons used in these anchors comprise a single-strap end on both the ground and air sides. On the ground side, the single-strap end is embedded in a cylinder of high-strength grout which fits in...
Article
In this study, an experimental campaign was conducted to characterize the length effect on the elasticity and tensile strength of clear spruce wood parallel to the grain direction. Four groups of specimens of different lengths, cut from the same log, were tested under the same conditions under longitudinal tensile loading. The cross-sectional area...
Conference Paper
The standard lightning waveforms used for the testing of aircraft are based on downward lightning. However, there is evidence suggesting that lightning to aircraft is different from negative downward lightning. Also, carbon fiber composite materials are being used extensively in wind turbines and aircraft which comprise small, sensitive electronics...
Conference Paper
Full-text available
Different factors such as age, location of timber within the tree, structural imperfections , load history such as wind and snow etc. can affect the material properties of timber. Consequently, there is a high variability in the mechanical properties which is sometimes referred to as 'random spatial variability'. In this work, the spatial variabili...
Article
Tensile experiments were performed on seven-layer non-laminated carbon fiber-reinforced polymer (CFRP) straps. A corresponding finite element (FE) model was developed and validated by the experimental results. The anchoring of the outermost tape layer by fusion bonding to the adjacent inner layer led to a non-uniform stress distribution among the t...
Article
In the current study, a random field-based size effect model has been proposed for the longitudinal tensile strength of clear timber. Since the failure mode is brittle, the problem is basically an extreme value problem of finding the distribution of minima of strength fields for specimens of different volumes. The stochastic response has been evalu...
Article
Different factors such as age, location of timber within the tree, structural imperfections, load history such as wind and snow etc. can affect the material properties of timber. Consequently, there is a high variability in the mechanical properties which is sometimes referred to as ‘random spatial variability’. In this work, the spatial variabilit...
Article
The standard lightning waveforms used for the testing of aircraft are based on downward lightning. However, there is evidence suggesting that lightning to aircraft is different from negative downward lightning. Also, carbon fiber composite materials are being used extensively in wind turbines and aircrafts which comprise small, sensitive electronic...
Article
A novel phenomenological model taking into account the creep-fatigue interaction in composite materials’ fatigue performance is introduced in this paper. The model is based on the derivation of a master curve by using existing experimental fatigue data from a wide range of composite laminates and adhesively bonded composite joints. The developed mo...
Conference Paper
Different factors such as age, location of timber within the tree, structural imperfections, load history such as wind and snow etc. can affect the material properties of timber. Consequently, there is a high variability in the mechanical properties which is sometimes referred to as ‘random spatial variability’. In this work, the spatial variabilit...
Chapter
The choice of a particular (an appropriate) fatigue theory for composite materials and structures is based on the material's behavior under the given loading pattern and the experience of the user. One of the most explicit and straightforward ways to represent experimental fatigue data is the S-. N diagram that is preferred to other ways since it r...
Chapter
Constant amplitude fatigue loading spectra stand for only a small percentage of the real loading of a structure, although they can be used to investigate the fatigue and fracture behavior of structural elements. The fatigue and fracture behavior of adhesively-bonded structural joints under different constant amplitude loading patterns has been expe...
Chapter
The fatigue behavior of adhesively-bonded glass fiber-reinforced polymer (GFRP) joints is affected by the loading sequence. Analysis of several experimental data for composite materials and adhesively-bonded composite joints showed that the loading sequence effect is a function of the loading type, the applied loading levels and the material under...
Chapter
A number of construction engineering applications for textiles made of composite materials are presented in this chapter. All these structures were fabricated by connecting several subcomponents, usually by using adhesives. Although composite materials are designated to be fatigue-insensitive, especially when compared to metallic ones, they also su...
Article
Similarly to the post-buckling behavior of steel girder webs, the post-wrinkling behavior of glass fiber-reinforced polymer (GFRP) cell-core sandwich webs can increase their ultimate shear strength. Post-wrinkling is, however, different from post-buckling since wrinkling is a local buckling instability mode that can occur in any part of the web. Fu...
Article
Full-text available
This paper presents new analytical model of asymmetric mixed-mode bending (MMB) specimen of adhesively bonded pultruded GFRP joints. An easily applicable relationship for the calculation of the strain energy release rate of the asymmetric MMB specimens is proposed based on the beam theory. The model is capable to analyze stacking sequence as well a...
Article
A new physically based model for the simulation of the imaginary part of the shear modulus-temperature (G″-T) curve of thermosets is introduced in this paper. The model is based on the modification of the G″-T equation used for thermoplastic polymers via the introduction of two new formulations regarding the calculation of the configuration probabi...
Article
The kink behavior of non-slender glass fiber-reinforced epoxy prismatic specimens of variable length and fiber volume fraction at temperatures ranging from 25. °C to 125. °C was investigated. Splitting failure occurred at the glassy state while kinking failure was observed at the glass transition state and buckling with subsequent post-peak kinking...
Article
After 17 and 15 years of use, respectively, a detailed inspection of a pedestrian bridge and a 5-story building structure composed of partly adhesively bonded pultruded glass fiber-reinforced polymer (GFRP) profiles was conducted accompanied by full-scale serviceability and destructive coupon testing on exchangeable profiles. The bridge is exposed...
Article
The failure mechanism of non-slender glass fiber-reinforced epoxy prismatic specimens subjected to axial compression and different temperatures was investigated. Digital image correlation was used to map and derive the failure modes. The failure mode changed from splitting failure at ambient temperature to kinking at the onset of the glass transiti...
Article
This paper demonstrates how the translucency of glass fiber-reinforced polymer (GFRP) laminates allows the derivation of their mechanical properties through optical measurements. Spectrophotometric, goniophotometric and tensile experiments were performed on unidirectional and cross-ply hand lay-up GFRP laminates with fiber volume fractions ranging...
Article
Fracture in the complex balsa cores of fiber-reinforced polymer (FRP) sandwich beams was analyzed. The cores were composed of high- and low-density balsa layers separated by a circular adhesive interface or FRP arch. The balsa layers were cut from panels which consisted of balsa blocks adhesively bonded together. Failure in the beams was initiated...
Article
In order to optimize the load-bearing behavior of sandwich structures and adapt it to specific requirements, their core may be composed of layers of different materials with tailored properties. These layers may consist not only of soft foam or honeycomb materials but also comprise stiff materials, e.g. timber, or even very stiff laminates in the c...