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This Special Issue contains selected papers from works presented at the 9th EASN International Conference on Innovation in Aviation & Space, which was successfully held in Athens, Greece, between the 3rd and 6th of September 2019
Spiros Pantelakis; Andreas Strohmayer. Special Issue “9th EASN International Conference on Innovation in Aviation & Space”. Aerospace 2021, 8, 110 .
AMA StyleSpiros Pantelakis, Andreas Strohmayer. Special Issue “9th EASN International Conference on Innovation in Aviation & Space”. Aerospace. 2021; 8 (4):110.
Chicago/Turabian StyleSpiros Pantelakis; Andreas Strohmayer. 2021. "Special Issue “9th EASN International Conference on Innovation in Aviation & Space”." Aerospace 8, no. 4: 110.
This Special Issue contains selected papers from works presented at the 10th EASN International Conference on Innovation in Aviation & Space to the Satisfaction of the European Citizens, which was held successfully from the 2nd until the 4th of September, 2020
Liberata Guadagno; Spiros Pantelakis; Andreas Strohmayer. Special Issue “10th EASN International Conference on Innovation in Aviation & Space to the Satisfaction of the European Citizens”. Aerospace 2021, 8, 111 .
AMA StyleLiberata Guadagno, Spiros Pantelakis, Andreas Strohmayer. Special Issue “10th EASN International Conference on Innovation in Aviation & Space to the Satisfaction of the European Citizens”. Aerospace. 2021; 8 (4):111.
Chicago/Turabian StyleLiberata Guadagno; Spiros Pantelakis; Andreas Strohmayer. 2021. "Special Issue “10th EASN International Conference on Innovation in Aviation & Space to the Satisfaction of the European Citizens”." Aerospace 8, no. 4: 111.
In the present work, a novel holistic component and process optimization index is introduced. The Index is aimed to provide a decision support tool for the optimization of aircraft composite components and manufacturing processes as well as for the selection of the appropriate manufacturing technique of a component when various techniques are considered as manufacturing options. The criteria involved in the index are quality, cost and environmental footprint functions which are considered to be interdependent. In the present concept quality is quantified through measurable technological features which are required for the component under consideration. Cost has been estimated by implementing the Activity Based Concept (ABC) using an in house developed tool. Environmental footprint is assessed by exploiting the ReCiPe method using the ‘open LCA’ software. The weight factor of each of the above criteria in the Index is calculated by using the Multi Criteria Decision (MCD) method Analytic Hierarchy Process (AHP). The Index developed has been applied to support the selection of the appropriate production technique for a typical aeronautical composite part. The alternative manufacturing options considered have been the Automated Fiber Placement (AFP) as well as the classical Autoclave manufacturing technique. By considering quality as the prevailing factor for meeting a decision the index confirms the advantage of the Autoclave process. Yet, by considering the environmental footprint and/or cost to be of equal or higher significance to quality, the implementation of the index demonstrates the clear advantage of AFP process.
Christos Katsiropoulos; Spiros Pantelakis. A Novel Holistic Index for the Optimization of Composite Components and Manufacturing Processes with Regard to Quality, Life Cycle Costs and Environmental Performance. Aerospace 2020, 7, 157 .
AMA StyleChristos Katsiropoulos, Spiros Pantelakis. A Novel Holistic Index for the Optimization of Composite Components and Manufacturing Processes with Regard to Quality, Life Cycle Costs and Environmental Performance. Aerospace. 2020; 7 (11):157.
Chicago/Turabian StyleChristos Katsiropoulos; Spiros Pantelakis. 2020. "A Novel Holistic Index for the Optimization of Composite Components and Manufacturing Processes with Regard to Quality, Life Cycle Costs and Environmental Performance." Aerospace 7, no. 11: 157.
Background The progressive evolution in hip replacement research is directed to follow the principles of bone and soft tissue sparing surgery. Regarding hip implants, a renewed interest has been raised towards short uncemented femoral implants. A heterogeneous group of short stems have been designed with the aim to approximate initial, post-implantation bone strain to the preoperative levels in order to minimize the effects of stress shielding. This study aims to investigate the biomechanical properties of two distinctly designed femoral implants, the TRI-LOCK Bone Preservation Stem, a shortened conventional stem and the Minima S Femoral Stem, an even shorter and anatomically shaped stem, based on experiments and numerical simulations. Furthermore, finite element models of implant–bone constructs should be evaluated for their validity against mechanical tests wherever it is possible. In this work, the validation was performed via a direct comparison of the FE calculated strain fields with their experimental equivalents obtained using the digital image correlation technique. Results Design differences between Trilock BPS and Minima S femoral stems conditioned different strain pattern distributions. A distally shifting load distribution pattern as a result of implant insertion and also an obvious decrease of strain in the medial proximal aspect of the femur was noted for both stems. Strain changes induced after the implantation of the Trilock BPS stem at the lateral surface were greater compared to the non-implanted femur response, as opposed to those exhibited by the Minima S stem. Linear correlation analyses revealed a reasonable agreement between the numerical and experimental data in the majority of cases. Conclusion The study findings support the use of DIC technique as a preclinical evaluation tool of the biomechanical behavior induced by different implants and also identify its potential for experimental FE model validation. Furthermore, a proximal stress-shielding effect was noted after the implantation of both short-stem designs. Design-specific variations in short stems were sufficient to produce dissimilar biomechanical behaviors, although their clinical implication must be investigated through comparative clinical studies.
I. Tatani; P. Megas; A. Panagopoulos; I. Diamantakos; Ph. Nanopoulos; Sp. Pantelakis. Comparative analysis of the biomechanical behavior of two different design metaphyseal-fitting short stems using digital image correlation. BioMedical Engineering OnLine 2020, 19, 1 -18.
AMA StyleI. Tatani, P. Megas, A. Panagopoulos, I. Diamantakos, Ph. Nanopoulos, Sp. Pantelakis. Comparative analysis of the biomechanical behavior of two different design metaphyseal-fitting short stems using digital image correlation. BioMedical Engineering OnLine. 2020; 19 (1):1-18.
Chicago/Turabian StyleI. Tatani; P. Megas; A. Panagopoulos; I. Diamantakos; Ph. Nanopoulos; Sp. Pantelakis. 2020. "Comparative analysis of the biomechanical behavior of two different design metaphyseal-fitting short stems using digital image correlation." BioMedical Engineering OnLine 19, no. 1: 1-18.
Nano-crystalline metals have attracted considerable attention over the past two decades due to their increased mechanical properties as compared to their microcrystalline counterparts. However, the behaviour of nano-crystalline metals is influenced by imperfections introduced during synthesis or heat treatment. These imperfections include pores, which are mostly located in the area of grain boundaries. To study the behaviour of multiphase nano-crystalline materials, a novel fully parametric algorithm was developed. The data required for implementing the developed numerical model were the volume fraction of the alloying elements and their basic properties as well as the density and the size of randomly distributed pores. To validate the developed algorithm, the alloy composition 75 wt% tungsten and 25 wt% copper was examined experimentally under compression tests. For the investigation, two batches of specimens were used; a batch having a coarse-grained microstructure with an average grain diameter of 150 nm and a nanocrystalline batch having a grain diameter of 100 nm, respectively. The porosity of both batches was derived to range between 9% and 10% based on X-ray diffraction analyses. The results of quasi-static compression testing revealed that the nanocrystalline W-Cu material exhibited brittle behaviour which was characterised by an elastic deformation that led to fracture without remarkable plasticity. A compressive strength of about 1100 MPa was derived which was more than double compared to conventional W-Cu samples. Finite element simulations of the behaviour of porous nano-crystalline materials were performed and compared with the respective experimental compression tests. The numerical model and experimental observations were in good agreement.
Panagiotis Bazios; Konstantinos Tserpes; Spiros Pantelakis. Modelling and Experimental Validation of the Porosity Effect on the Behaviour of Nano-Crystalline Materials. Metals 2020, 10, 821 .
AMA StylePanagiotis Bazios, Konstantinos Tserpes, Spiros Pantelakis. Modelling and Experimental Validation of the Porosity Effect on the Behaviour of Nano-Crystalline Materials. Metals. 2020; 10 (6):821.
Chicago/Turabian StylePanagiotis Bazios; Konstantinos Tserpes; Spiros Pantelakis. 2020. "Modelling and Experimental Validation of the Porosity Effect on the Behaviour of Nano-Crystalline Materials." Metals 10, no. 6: 821.
In the present chapter, the evolution of aeronautical materials is presented. The chapter focuses on the historical development of aeronautical materials from the first usage of metals, for the aerospace purpose, to the massive aeronautical implementation of composite materials nowadays. Also described in this chapter are the European policies which are driven by the needs of the global economy and the environmental protection in order to reduce the fuel consumption and the CO2 emissions. Additionally, innovative materials and modern manufacturing techniques are shown so as to achieve the aforementioned environmental and economic goals.
Spiros Pantelakis. Historical Development of Aeronautical Materials. Revolutionizing Aircraft Materials and Processes 2020, 1 -19.
AMA StyleSpiros Pantelakis. Historical Development of Aeronautical Materials. Revolutionizing Aircraft Materials and Processes. 2020; ():1-19.
Chicago/Turabian StyleSpiros Pantelakis. 2020. "Historical Development of Aeronautical Materials." Revolutionizing Aircraft Materials and Processes , no. : 1-19.
This Special Issue contains selected papers from works presented at the 8th EASN–CEAS (European Aeronautics Science Network–Council of European Aerospace Societies) Workshop on Manufacturing for Growth and Innovation, which was held in Glasgow, UK, 4–7 September 2018
Spiros Pantelakis; Konstantinos Kontis. Special Issue “8th EASN–CEAS Workshop on Manufacturing for Growth and Innovation”. Aerospace 2019, 6, 84 .
AMA StyleSpiros Pantelakis, Konstantinos Kontis. Special Issue “8th EASN–CEAS Workshop on Manufacturing for Growth and Innovation”. Aerospace. 2019; 6 (8):84.
Chicago/Turabian StyleSpiros Pantelakis; Konstantinos Kontis. 2019. "Special Issue “8th EASN–CEAS Workshop on Manufacturing for Growth and Innovation”." Aerospace 6, no. 8: 84.
Total hip replacement has recently followed a progressive evolution towards principles of bone- and soft-tissue-sparing surgery. Regarding femoral implants, different stem designs have been developed as an alternative to conventional stems, and there is a renewed interest towards short versions of uncemented femoral implants. Based on both experimental testing and finite element modeling, the proposed study has been designed to compare the biomechanical properties and clinical performance of the newly introduced short-stem Minima S, for which clinical data are lacking with an older generation stem, the Trilock Bone Preservation Stem with an established performance record in short to midterm follow-up. In the experimental study, the transmission of forces as measured by cortical surface-strain distribution in the proximal femur will be evaluated using digital image correlation (DIC), first on the non-implanted femur and then on the implanted stems. Finite element parametric models of the bone, the stem and their interface will be also developed. Finite element predictions of surface strains in implanted composite femurs, after being validated against biomechanical testing measurements, will be used to assist the comparison of the stems by deriving important data on the developed stress and strain fields, which cannot be measured through biomechanical testing. Finally, a prospective randomized comparative clinical study between these two stems will be also conducted to determine (1) their clinical performance up to 2 years’ follow-up using clinical scores and gait analysis (2) stem fixation and remodeling using a detailed radiographic analysis and (3) incidence and types of complications. Our study would be the first that compares not only the clinical and radiological outcome but also the biomechanical properties of two differently designed femoral implants that are theoretically classified in the same main category of cervico-metaphyseal-diaphyseal short stems. We can hypothesize that even these subtle variations in geometric design between these two stems may create different loading characteristics and thus dissimilar biomechanical behaviors, which in turn could have an influence to their clinical performance. International Standard Randomized Controlled Trial Number, ID: ISRCTN10096716 . Retrospectively registered on May 8 2018.
I. Tatani; A. Panagopoulos; I. Diamantakos; G. Sakellaropoulos; Sp Pantelakis; P. Megas. Comparison of two metaphyseal-fitting (short) femoral stems in primary total hip arthroplasty: study protocol for a prospective randomized clinical trial with additional biomechanical testing and finite element analysis. Trials 2019, 20, 1 -13.
AMA StyleI. Tatani, A. Panagopoulos, I. Diamantakos, G. Sakellaropoulos, Sp Pantelakis, P. Megas. Comparison of two metaphyseal-fitting (short) femoral stems in primary total hip arthroplasty: study protocol for a prospective randomized clinical trial with additional biomechanical testing and finite element analysis. Trials. 2019; 20 (1):1-13.
Chicago/Turabian StyleI. Tatani; A. Panagopoulos; I. Diamantakos; G. Sakellaropoulos; Sp Pantelakis; P. Megas. 2019. "Comparison of two metaphyseal-fitting (short) femoral stems in primary total hip arthroplasty: study protocol for a prospective randomized clinical trial with additional biomechanical testing and finite element analysis." Trials 20, no. 1: 1-13.
Nanocrystalline metals have been the cause of substantial intrigue over the past two decades due to their high strength, which is highly sensitive to their microstructure. The aim of the present project is to develop a finite element two-phase model that is able to predict the elastic moduli and the yield strength of nanostructured material as functions of their microstructure. The numerical methodology uses representative volume elements (RVEs) in which the material microstructure, i.e., the grains and grain boundaries, is presented utilizing the three-dimensional (3D) Voronoi algorithm. The implementation of the 3D Voronoi particles was performed on the nanostructure investigation of ultrafine materials by SEM and TEM. Proper material properties for the grain interiors (GI) and grain boundaries (GB) were computed using the Hall-Petch equation and a dislocation-based analytical approach, respectively. The numerical outcomes show that the Young’s Modulus of nanostructured copper increased by increasing the crystallite volume fraction, while the yield strength increased by decreasing the grain size. The numerical predictions were strongly confirmed in opposition to finite element outcomes, experimental results from the open literature, and predictions from the rule of mixtures and the Mori-Tanaka analytical models.
Panagiotis Bazios; Konstantinos Tserpes; Spiros G. Pantelakis. Numerical Computation of Material Properties of Nanocrystalline Materials Utilizing Three-Dimensional Voronoi Models. Metals 2019, 9, 202 .
AMA StylePanagiotis Bazios, Konstantinos Tserpes, Spiros G. Pantelakis. Numerical Computation of Material Properties of Nanocrystalline Materials Utilizing Three-Dimensional Voronoi Models. Metals. 2019; 9 (2):202.
Chicago/Turabian StylePanagiotis Bazios; Konstantinos Tserpes; Spiros G. Pantelakis. 2019. "Numerical Computation of Material Properties of Nanocrystalline Materials Utilizing Three-Dimensional Voronoi Models." Metals 9, no. 2: 202.
In the present work the carbon footprint and the financial viability of different materials, manufacturing scenarios, as well as recycling scenarios, associated with the production of aeronautical structural components are assessed. The materials considered were carbon fiber reinforced epoxy and carbon fiber reinforced PEEK (polyetheretherketone). The manufacturing techniques compared were the autoclave, resin transfer molding (RTM) and cold diaphragm forming (CDF). The recycling scenarios included mechanical recycling and pyrolysis. For this purpose, Life Cycle Analysis (LCA) and Life Cycle Costing (LCC) models were developed and implemented for the case of a helicopter’s canopy production. The results of the study pointed out that producing the canopy by using carbon fiber reinforced thermosetting composites and involving RTM as the manufacturing process is the optimal route both in terms of environmental and financial efficiency. The environmental and financial efficiency of the scenarios including thermoplastic composites as the material of choice is impaired from both the high embodied energy and raw material cost of PEEK. The scenarios investigated do not account for potential benefits arising from the recyclability and the improved reusability of thermoplastic matrices as compared to thermosetting ones. This underlines the need for a holistic aircraft structural optimization approach including not only performance and weight but also cost and environmental criteria.
Christos V. Katsiropoulos; Andreas Loukopoulos; Spiros G. Pantelakis. Comparative Environmental and Cost Analysis of Alternative Production Scenarios Associated with a Helicopter’s Canopy. Aerospace 2019, 6, 3 .
AMA StyleChristos V. Katsiropoulos, Andreas Loukopoulos, Spiros G. Pantelakis. Comparative Environmental and Cost Analysis of Alternative Production Scenarios Associated with a Helicopter’s Canopy. Aerospace. 2019; 6 (1):3.
Chicago/Turabian StyleChristos V. Katsiropoulos; Andreas Loukopoulos; Spiros G. Pantelakis. 2019. "Comparative Environmental and Cost Analysis of Alternative Production Scenarios Associated with a Helicopter’s Canopy." Aerospace 6, no. 1: 3.
Multi Wall Carbon Nanotubes (MWCNTs) and Polyhedral Oligomeric Silsesquioxanes (POSS) are common additives to simultaneously enhance electrical conductivity and flame resistance. In the present work, the synergistic effect of the addition of MWCNTs and two different POSS compounds, DodecaPhenyl POSS (DPHPOSS) and Glycidyl POSS (GPOSS), on the mechanical behavior of multifunctional polymers subjected both to quasi-static as well as to fatigue loading was investigated. The results of the mechanical tests were discussed supported by Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) analyses. The results showed that the incorporation of MWCNTs in the resin containing GPOSS determines a slight decrease in the flexural modulus compared to the unfilled resin. The material filled with MWCNTs and DPHPOSS shows a higher reduction of the flexural modulus as compared to the other analyzed materials. The same trend was observed also for the flexural strength; more than 50% decrease of the flexural strength of the material filled with MWCNTs and DPHPOSS is detected. As far as the fatigue is concerned, it seems that the incorporation of the flame retardants led to an appreciable decrease in the fatigue life. The decrease in the mechanical properties of the nanofilled resin loaded with DPHPOSS is most likely due to the presence of aggregates of DPHPOSS crystals in the matrix. This hypothesis is confirmed by EDX analysis which shows that DPHPOSS forms some small aggregates, whereas GPOSS, being molecularly solubilized in the epoxy formulation, shows mechanical performance more similar to the sample loaded only with carbon nanotubes.
P.V. Polydoropoulou; Ch.V. Katsiropoulos; Sp.G. Pantelakis; Marialuigia Raimondo; L. Guadagno. A critical assessment of multifunctional polymers with regard to their potential use in structural applications. Composites Part B: Engineering 2018, 157, 150 -162.
AMA StyleP.V. Polydoropoulou, Ch.V. Katsiropoulos, Sp.G. Pantelakis, Marialuigia Raimondo, L. Guadagno. A critical assessment of multifunctional polymers with regard to their potential use in structural applications. Composites Part B: Engineering. 2018; 157 ():150-162.
Chicago/Turabian StyleP.V. Polydoropoulou; Ch.V. Katsiropoulos; Sp.G. Pantelakis; Marialuigia Raimondo; L. Guadagno. 2018. "A critical assessment of multifunctional polymers with regard to their potential use in structural applications." Composites Part B: Engineering 157, no. : 150-162.
A multi-scale modeling approach for simulating the tensile behavior of the corroded aluminum alloy 2024 T3 was developed, accounting for both the geometrical features of corrosion damage and the effect of corrosion-induced hydrogen embrittlement (HE). The approach combines two Finite Element (FE) models: a model of a three-dimensional Representative Unit Cell (RUC), representing an exfoliated area and its correspondent hydrogen embrittled zone (HEZ), and a model of the tensile specimen. The models lie at the micro- and macro-scales, respectively. The characteristics of the HEZ are determined from measurements of nanoindentation hardness, conducted on pre-corroded specimens. Using the model of the RUC, the local homogenized mechanical behavior of the corroded material is simulated. Then, the behavior of the exfoliated areas is assigned into different areas (elements) of the tensile specimen and final analyses are performed to simulate the tensile behavior of the corroded material. The approach was applied to model specimens after 8, 16 and 24 h exposure periods of the Exfoliation Corrosion (EXCO) test. For validation of the approach, tensile tests were used. The numerical results show that this approach is suitable for accurately simulating the tensile behavior of pre-corroded experimental specimens, accounting for both geometrical features of corrosion damage and corrosion-induced HE.
Marina C. Vasco; Konstantinos Tserpes; Spiros G. Pantelakis. Numerical Simulation of Tensile Behavior of Corroded Aluminum Alloy 2024 T3 Considering the Hydrogen Embrittlement. Metals 2018, 8, 56 .
AMA StyleMarina C. Vasco, Konstantinos Tserpes, Spiros G. Pantelakis. Numerical Simulation of Tensile Behavior of Corroded Aluminum Alloy 2024 T3 Considering the Hydrogen Embrittlement. Metals. 2018; 8 (1):56.
Chicago/Turabian StyleMarina C. Vasco; Konstantinos Tserpes; Spiros G. Pantelakis. 2018. "Numerical Simulation of Tensile Behavior of Corroded Aluminum Alloy 2024 T3 Considering the Hydrogen Embrittlement." Metals 8, no. 1: 56.
Spyros G Pantelakis; Christos V Katsiropoulos; Panagiota V Polydoropoulou. Assessing the compression after impact behaviour of innovative multifunctional composites. Nanomaterials and Nanotechnology 2016, 6, 1 .
AMA StyleSpyros G Pantelakis, Christos V Katsiropoulos, Panagiota V Polydoropoulou. Assessing the compression after impact behaviour of innovative multifunctional composites. Nanomaterials and Nanotechnology. 2016; 6 ():1.
Chicago/Turabian StyleSpyros G Pantelakis; Christos V Katsiropoulos; Panagiota V Polydoropoulou. 2016. "Assessing the compression after impact behaviour of innovative multifunctional composites." Nanomaterials and Nanotechnology 6, no. : 1.
An assessment of innovative adhesive bonding process has been performed with regard to quality and cost. In this frame, the effect of two different atmospheric pressure plasma surface treatment conditions on the fracture toughness behaviour of adhesively bonded joints was experimentally investigated. Furthermore, the mechanical performance of a newly developed aerospace structural adhesive has been characterised experimentally in order to assess the quality of the bonded elements. To assess the feasibility of the new process, a complete cost-estimation analysis of the process has been carried out based on the activity-based costing modelling approach, thus serving to the estimation of the total cost/duration of the process. To this end, the newly developed process is assessed with regard to quality and cost. It could be shown that the new process offers tempting alternatives to the existing adhesive bonding and joining processes used in the aeronautic industry.
Ch.V. Katsiropoulos; Sp.G. Pantelakis. An overall assessment of a new adhesive bonding process for composite materials, with regard to quality and cost. Plastics, Rubber and Composites 2015, 45, 22 -30.
AMA StyleCh.V. Katsiropoulos, Sp.G. Pantelakis. An overall assessment of a new adhesive bonding process for composite materials, with regard to quality and cost. Plastics, Rubber and Composites. 2015; 45 (1):22-30.
Chicago/Turabian StyleCh.V. Katsiropoulos; Sp.G. Pantelakis. 2015. "An overall assessment of a new adhesive bonding process for composite materials, with regard to quality and cost." Plastics, Rubber and Composites 45, no. 1: 22-30.
The fatigue crack growth behavior under constant amplitude and under single overload of 2024 aluminum alloy in sheet and plate product form has been investigated. Constant amplitude fatigue crack growth tests showed superior crack growth resistance of the plate attributed to a pronounced roughness induced crack closure as a result of the coarse and elongated grain structure. Crack growth tests with single overload showed that the retardation effect caused by the overload is not primarily influenced by roughness crack closure at the crack path. In this case, the sheet material with lower yield strength revealed a higher retardation effect than the plate material. The observed crack growth behavior has been simulated with the LTSM-F model, which accounts for retardation of crack growth after an overload due to material strain hardening at the crack front. Dissimilar strain hardening at the crack tip due to different yield strength for the sheet and plate has been considered by means of strength gradients inside the overload plastic zone. The analytical results confirmed the observed material crack growth trends.
A.T. Kermanidis; Sp.G. Pantelakis. Prediction of crack growth following a single overload in aluminum alloy with sheet and plate microstructure. Engineering Fracture Mechanics 2011, 78, 2325 -2337.
AMA StyleA.T. Kermanidis, Sp.G. Pantelakis. Prediction of crack growth following a single overload in aluminum alloy with sheet and plate microstructure. Engineering Fracture Mechanics. 2011; 78 (11):2325-2337.
Chicago/Turabian StyleA.T. Kermanidis; Sp.G. Pantelakis. 2011. "Prediction of crack growth following a single overload in aluminum alloy with sheet and plate microstructure." Engineering Fracture Mechanics 78, no. 11: 2325-2337.
A concept has been devised to assess the effect of existing corrosion damage on the residual tensile properties of structural alloys and applied for the magnesium alloy AZ31. The concept based on the use of a radial basis function neural network. An extensive experimental investigation, including metallographic corrosion characterization and mechanical testing of pre-corroded AZ31 magnesium alloy specimens, was carried out to derive the necessary data for the training and the prediction module of the developed neural network model. The proposed concept was exploited to successfully predict: the gradual tensile property degradation of the alloy AZ31 to the results of gradually increasing corrosion damage with increasing corrosion exposure.
V. Kappatos; Apostolos Chamos; Sp.G. Pantelakis. Assessment of the effect of existing corrosion on the tensile behaviour of magnesium alloy AZ31 using neural networks. Materials & Design 2010, 31, 336 -342.
AMA StyleV. Kappatos, Apostolos Chamos, Sp.G. Pantelakis. Assessment of the effect of existing corrosion on the tensile behaviour of magnesium alloy AZ31 using neural networks. Materials & Design. 2010; 31 (1):336-342.
Chicago/Turabian StyleV. Kappatos; Apostolos Chamos; Sp.G. Pantelakis. 2010. "Assessment of the effect of existing corrosion on the tensile behaviour of magnesium alloy AZ31 using neural networks." Materials & Design 31, no. 1: 336-342.
The effects of temper condition and corrosion on the fatigue behavior of a laser beam welded Al–Cu–Mg–Ag alloy (2139) have been investigated. Natural aging (T3 temper) and artificial aging (T8 temper) have been applied prior to welding. Corrosion testing has been performed by exposing the welded specimens to a salt spray medium for 720 h. Aging influences the corrosion behavior of laser welds. In the T3 temper, corrosion attack is in the form of pitting in the weld area, while in the T8 temper corrosion is in the form of pitting and intergranular corrosion in the base metal. In the latter case corrosion is attributed to the presence of grain boundary precipitates. Corrosion degrades the fatigue behavior of 2139 welds. The degradation is equal for both the T3 and T8 tempers and for the corrosion exposure selected in this study corresponds to a 52% reduction in fatigue limit. In both cases fatigue crack initiation is associated with corrosion pits, which act as stress raisers. In the T3 temper, the fatigue crack initiation site is at the weld metal/heat affected zone interface, while for the T8 temper the initiation site is at the base metal. Fatigue crack initiation in uncorroded 2139 welds occurs at the weld toe at the root side, the weld reinforcement playing a principal role as stress concentration site. The fatigue crack propagates through the partially melted zone and the weld metal in all cases. The findings in this paper present useful information for the selection of appropriate heat treatment conditions, to facilitate control of the corrosion behavior in aluminium welds, which is of great significance for their fatigue performance.
A.T. Kermanidis; A.D. Zervaki; G.N. Haidemenopoulos; Sp.G. Pantelakis. Effects of temper condition and corrosion on the fatigue performance of a laser-welded Al–Cu–Mg–Ag (2139) alloy. Materials & Design 2010, 31, 42 -49.
AMA StyleA.T. Kermanidis, A.D. Zervaki, G.N. Haidemenopoulos, Sp.G. Pantelakis. Effects of temper condition and corrosion on the fatigue performance of a laser-welded Al–Cu–Mg–Ag (2139) alloy. Materials & Design. 2010; 31 (1):42-49.
Chicago/Turabian StyleA.T. Kermanidis; A.D. Zervaki; G.N. Haidemenopoulos; Sp.G. Pantelakis. 2010. "Effects of temper condition and corrosion on the fatigue performance of a laser-welded Al–Cu–Mg–Ag (2139) alloy." Materials & Design 31, no. 1: 42-49.
A concept for the optimization of manufacturing processes of composite material components with regard to product’s quality and cost is introduced and applied for the case of thermoplastic composite helicopter canopies produced by ‘Cold’ Diaphragm Forming (CDF) process. The proposed methodology relies on the consideration of the processes thermal cycle as decisive for the component’s quality and cost. Quality and cost sensitivity analyses were made to derive material dependent Quality Functions (QFs) and process dependent Cost Estimation Relationships (CERs). QFs and CERs are exploited to derive iteratively the optimal thermal cycle. The processes thermal cycle is numerically simulated to allow for its virtual application on the material. To perform the optimization procedure a new software tool is developed. CDF heating system configuration along with the optimal thermal cycle for producing helicopter canopies were obtained. The results of the study were successfully exploited by EUROCOPTER to produce 1:3 scale prototypes.
Sp.G. Pantelakis; Ch.V. Katsiropoulos; G.N. Labeas; H. Sibois. A concept to optimize quality and cost in thermoplastic composite components applied to the production of helicopter canopies. Composites Part A: Applied Science and Manufacturing 2009, 40, 595 -606.
AMA StyleSp.G. Pantelakis, Ch.V. Katsiropoulos, G.N. Labeas, H. Sibois. A concept to optimize quality and cost in thermoplastic composite components applied to the production of helicopter canopies. Composites Part A: Applied Science and Manufacturing. 2009; 40 (5):595-606.
Chicago/Turabian StyleSp.G. Pantelakis; Ch.V. Katsiropoulos; G.N. Labeas; H. Sibois. 2009. "A concept to optimize quality and cost in thermoplastic composite components applied to the production of helicopter canopies." Composites Part A: Applied Science and Manufacturing 40, no. 5: 595-606.
The present investigation aims to inquire whether Al cladding of 2024 aluminum alloy specimens could provide, additionally to the expected protection against corrosion damage, also a protection against the corrosion induced hydrogen embrittlement of the alloy. The latter is observed when bare 2024 material is subjected to laboratory exfoliation corrosion exposure also in the absence of mechanical loading. Furthermore, the study aims to ponder on the question whether local Al cladding at small regions of the specimen surface might suffice for protecting the specimen against corrosion damage and hydrogen embrittlement. The work comprises the results of an extensive experimental investigation including tensile tests on precorroded 2024 specimens protected through both complete and local surface Al cladding, metallographic and fractographic analyses as well as measurements of the hydrogen uptake during the corrosion process.
P.V. Petroyiannis; Sp.G. Pantelakis; G.N. Haidemenopoulos. Protective role of local Al cladding against corrosion damage and hydrogen embrittlement of 2024 aluminum alloy specimens. Theoretical and Applied Fracture Mechanics 2005, 44, 70 -81.
AMA StyleP.V. Petroyiannis, Sp.G. Pantelakis, G.N. Haidemenopoulos. Protective role of local Al cladding against corrosion damage and hydrogen embrittlement of 2024 aluminum alloy specimens. Theoretical and Applied Fracture Mechanics. 2005; 44 (1):70-81.
Chicago/Turabian StyleP.V. Petroyiannis; Sp.G. Pantelakis; G.N. Haidemenopoulos. 2005. "Protective role of local Al cladding against corrosion damage and hydrogen embrittlement of 2024 aluminum alloy specimens." Theoretical and Applied Fracture Mechanics 44, no. 1: 70-81.
The effect of different artificial aging heat treatment on the quality of A357 alloy cast ingot specimens is evaluated. The experiments include artificial aging of the specimens at 155, 175 and 205 °C for various aging times. The dependencies of hardness and tensile properties of the aged alloys on the aging conditions are derived. Rockwell hardness and yield strength could be correlated using a linear function. The material quality is evaluated such as to be application-specific. By relating quality to yield strength quality could be assessed using the Rockwell hardness measurements. To account in quality evaluation also for tensile ductility quality indices are exploited. The dependencies of the involved quality indices on the aging conditions are derived. Same values of the same quality index are found to correspond to different combinations of tensile properties. The quality index QD proposed by the authors is exploited to devise quality maps; they involve iso-quality lines and the corresponding combinations of tensile properties. A quality map for the cast ingot of A357 alloy is presented. The map may be exploited to select the aging conditions such as to tailor the alloy properties to a certain engineering application.
N.D. Alexopoulos; Sp.G. Pantelakis. Quality evaluation of A357 cast aluminum alloy specimens subjected to different artificial aging treatment. Materials & Design (1980-2015) 2004, 25, 419 -430.
AMA StyleN.D. Alexopoulos, Sp.G. Pantelakis. Quality evaluation of A357 cast aluminum alloy specimens subjected to different artificial aging treatment. Materials & Design (1980-2015). 2004; 25 (5):419-430.
Chicago/Turabian StyleN.D. Alexopoulos; Sp.G. Pantelakis. 2004. "Quality evaluation of A357 cast aluminum alloy specimens subjected to different artificial aging treatment." Materials & Design (1980-2015) 25, no. 5: 419-430.