10 results on '"Antonaci, Paola"'
Search Results
2. Non-linear tendon fatigue life under uncertainties.
- Author
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Rodriguez Reinoso, Mariana, Antonaci, Paola, Pugno, Nicola M., and Surace, Cecilia
- Subjects
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MONTE Carlo method , *TENDONS , *CYCLIC loads , *TISSUES , *RANGE of motion of joints , *TENSION loads - Abstract
Tendons play a pivotal role in facilitating joint movement by transmitting muscular forces to bones. The intricate hierarchical structure and diverse material composition of tendons contribute to their non-linear mechanical response. However, comprehensively grasping their mechanical properties poses a challenge due to inherent variability in biological tissues. This necessitates a thorough examination of uncertainties associated with properties measurements, particularly under diverse loading conditions. Given the cyclic loading experienced by tendons throughout an individual's lifespan, understanding their mechanical behaviour under such circumstances becomes crucial. This study addresses this need by introducing a generalised Paris Erdogan Law tailored for non-linear materials. To examine uncertainties within this proposed framework, Monte Carlo Analysis is employed. This approach allows for a thorough exploration of the uncertainties associated with tendon mechanics, contributing to a more robust comprehension of their behaviour under cyclic loading conditions. Finally, self-healing has been integrated into the fatigue law of tendons through the proposal of a healing function, formulated as a polynomial function of the maximum stress. This approach allows to account for an increase in the number of cycles for each stress value due to self-repair after the damage event generated by long-term cycling load over the individual's life span. • -Development of a Generalised Paris Erdogan law for non-linear materials such as soft tissues. • -Use of Monte Carlo Analysis for robust comprehension of tendon mechanics uncertainties. • -Estimation of mechanical parameters C and m_p for the PE law in tendon cases. • -Introduction of Healing Function to observe increased cycles due to self-healing effect. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
3. Photo-polymerization for additive manufacturing of composite solid propellants.
- Author
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Garino, Simone, Antonaci, Paola, Pastrone, Dario, Sangermano, Marco, and Maggi, Filippo
- Subjects
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SOLID propellants , *PROPELLANTS , *PREPOLYMERS , *HAZARDOUS substances , *AMMONIUM sulfate , *MANUFACTURING processes - Abstract
The established state-of-the-art for composite solid propellant grain manufacture consists in mix-cast-cure process using hazardous chemicals and specific molds for propellant forming. In most of the cases, polyaddition of oligomers involves isocyanate functional groups. Construction constraints limit the feasibility of propellant geometries, confining the pressure-time history of rocket motors to some established configurations. Composition pot-life becomes one of the most important parameters in the definition of correlated industrial processes. An additive manufacturing process for propellant grain production based on UV curing has been recently proposed for patenting. This technique enables more complex grain geometries, paving the way for new propulsive missions, thanks to customized thrust-time profiles or local composition fine tuning. The new curative method makes innovative use of pre-polymers, replacing isocyanates with UV-sensitive components characterized by lower chemical hazard for operators. The paper illustrates the experimental results obtained during the preliminary test campaign on propellant inert simulators, produced as lab-scale proof of concept. The activity targeted mono-layer samples, focusing on binder properties. Dynamic-mechanical thermal analysis, thermal-gravimetric analysis, and stress–strain tests have been carried out to measure mechanical and physical characteristics of different formulations. Both hydroxyl-terminated polybutadiene (HTPB) and polybutadiene diacrylate (PBDDA) binders have been considered, using ammonium sulfate as substitute of ammonium perchlorate. Aluminized and non-aluminized samples have been manufactured to evaluate the impact of opaque-reflective materials during the UV curing process. The reported analyses show comparable results for both the new UV-cured materials and demonstrate the feasibility of propellants based on isocyanate-free process. • Solid propellants are produced without isocyanates using photo-polymerization. • Photo-polymerization can work with HTPB, PBDDA, and some nonfunctional polymers. • Removal of isocyanates can reduce operator risks and environmental issues. • Photo-polymerization enables additive manufacturing of solid propellant grains. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
4. Experimental study for the evaluation of creep in concrete through thermal measurements
- Author
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Bocca, Pietro Giovanni and Antonaci, Paola
- Subjects
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THERMAL analysis , *ANALYTICAL chemistry , *NONDESTRUCTIVE testing , *COMMERCIAL product testing - Abstract
Abstract: This investigation, conducted at the Non-Destructive Testing Laboratory at the Politecnico di Torino, made it possible to establish an experimental relationship between specific creep values measured in concrete test pieces obtained from different mixes and the decrease in temperature observed in identical test pieces at the end of low-intensity short-duration compressive tests. This relationship is independent of type of mix and therefore has general validity: it can be used to make qualitative predictions about creep without having to perform long duration tests. It may lead to interesting developments in various applications, especially in the field of structural diagnosis. [Copyright &y& Elsevier]
- Published
- 2005
- Full Text
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5. Geopolymer technology for application-oriented dense and lightened materials. Elaboration and characterization.
- Author
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Palmero, Paola, Formia, Alessandra, Antonaci, Paola, Brini, Simona, and Tulliani, Jean-Marc
- Subjects
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KAOLIN , *ACTIVATORS (Chemistry) , *CHEMICAL sample preparation , *FLEXURE , *MATERIALS compression testing - Abstract
In this paper, dense and lightened geopolymer materials based on calcined kaolin and different alkali activators were prepared and submitted to a physical and mechanical characterization: density measurement, mechanical tests (flexural and compressive tests) and thermal conductivity analysis were carried out. First, pastes were prepared by using both sodium and potassium silicate solutions. It was found that the chemical composition of the alkali solution has a minor effect on the flexural strength, while it significantly affects compressive strength and stiffness in three-point-bending, being the best performance obtained with the sodium silicate solution. Then, starting from this paste formulation, different dense materials were prepared, including mortars and composite samples containing a commercial acrylate emulsion (Primal B60A), used to improve the workability of the pastes and the mechanical properties of the cured samples. The Primal-free dense specimens showed good compressive strengths (20–30 MPa) in line with literature for metakaolin-based materials. However, Primal addition was effective in enhancing the compressive strength up to 46 MPa. Finally, different sets of low-density materials were prepared: lightweight samples, produced with expanded glass spheres (Poraver ® ) and macroporous samples, foamed with hydrogen peroxide in different amounts. All these samples appeared homogenous with very limited segregation phenomena. The thermal conductivity ranged from 0.12 to 0.78 W/m K, in function of the density of the samples: the lowest values, presented by the macroporous materials, were comparable with those of most commonly used building insulation materials. As a whole, this work has shown the versatility of geopolymers towards the elaboration of a variety of materials with different macroscopic features: from pastes, to mortars, to lightweight samples, to macroporous samples. Finally, the feasibility of producing bilayer materials has been assessed: samples made by superimposing a lightened layer over a millimetric layer of geopolymer paste or mortars after its partial curing were successfully prepared. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
6. Epoxy monomers consolidant for lime plaster cured via a redox activated cationic polymerization.
- Author
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Formia, Alessandra, Tulliani, Jean-Marc, Antonaci, Paola, and Sangermano, Marco
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EPOXY resins , *REDOX polymers , *MONOMERS , *LIME (Minerals) , *ADDITION polymerization , *PLASTER , *CURING - Abstract
Epoxy resins, widely used in conservation, still remain controversial materials. Considering some of the drawbacks that currently limit the application of epoxy consolidants, we present the application of the cationic ring opening polymerization as a novel method to cure the epoxy monomer in the restoration field. The cationic polymerization was carried out through a redox system based on the reduction of the iodonium salt in the presence of ascorbic acid catalyzed by a copper salt. The use of this initiator system for carrying out a suitable consolidant for lime plaster is considered. First, the film properties of the cured films were investigated. Then, the formulation was applied on a sample of plaster and its compatibility was verified. Its effectiveness as a consolidant product is explored through the evaluation of chromatic changes, mechanical strength, morphology of the re-aggregated material, and changes of the surface properties. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
7. Non-destructive evaluation of ductile-porous versus brittle 3D printed vascular networks in self-healing concrete.
- Author
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Shields, Yasmina, Tsangouri, Eleni, Riordan, Claire, De Nardi, Cristina, Godinho, Jose Ricardo Assunção, Ooms, Ticho, Antonaci, Paola, Palmer, Dave, Al-Tabbaa, Abir, Jefferson, Tony, De Belie, Nele, and Van Tittelboom, Kim
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SELF-healing materials , *ULTRASONIC testing , *DIGITAL image correlation , *ACOUSTIC emission , *CONCRETE - Abstract
Additive manufacturing (AM) can produce complex vascular network configurations, yet limited testing has been done to characterize the damage and healing behavior of concrete with embedded networks for self-healing. In this study, different AM methods and network wall materials were used to produce vascular networks for self-healing concrete prisms, where their load-response behavior, healing efficiency and microstructure were evaluated using non-destructive techniques: acoustic emission (AE), ultrasonic pulse velocity (UPV), digital image correlation (DIC), and X -ray computed tomography (CT). The types of healing agent release mechanisms that were studied include a ductile-porous network that supplies fluid from its pores and a brittle network that fractures under load to release fluid. DIC coupled with AE verified debonding of ductile-porous networks from the cementitious matrix, and was able to track damage progression as well as healing for all networks with load regains up to 56 % and stiffness regains up to 91 % using polyurethane. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
8. Novel production of macrocapsules for self-sealing mortar specimens using stereolithographic 3D printers.
- Author
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Riordan, Claire, Anglani, Giovanni, Inserra, Barbara, Palmer, Dave, Al-Tabbaa, Abir, Tulliani, Jean-Marc, and Antonaci, Paola
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MORTAR , *3-D printers , *WATER repellents , *THREE-dimensional printing , *CEMENT - Abstract
The use of capsule-based technology for self-sealing and self-healing cementitious systems has been extensively investigated for both macro- and microencapsulated additions. In this study, macrocapsules, produced using a novel technique were characterised and compared, evaluating mechanical triggering, bonding with the cementitious matrix, and self-sealing efficiency upon integration into cementitious mortar specimens. Macrocapsules containing a commercially available water repellent agent were produced in two ways. Stereolithographic additive manufacturing (3D printing) was used to produce novel rigid acrylate macrocapsules as well as alumina ones. Cementitious macrocapsules produced with a rolling technique were also used as a comparison. The capsules were characterised in terms of watertightness, water uptake, and shell morphology. Following this, the capsules were integrated into cement mortar prisms and subjected to controlled cracking by three-point bending to evaluate the triggering and subsequent self-sealing effect. The results highlighted influential process parameters that can be optimised and explored for further capsule-based self-sealing in structural applications. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
9. Valorisation of alumino-silicate stone muds: From wastes to source materials for innovative alkali-activated materials.
- Author
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Palmero, Paola, Formia, Alessandra, Tulliani, Jean-Marc, and Antonaci, Paola
- Subjects
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ALUMINUM silicates , *MUD , *WASTE management , *MECHANICAL behavior of materials , *ALKALI metals , *THERMOPHYSICAL properties - Abstract
Impressive amounts of wastes are produced yearly by extraction and transformation of natural stones. This work addresses the finest fraction of these wastes, named stone muds, and particularly those with a siliceous composition. The disposal in dump of these muds implies high costs, whereas their surface landing poses serious challenges, since they can damage the environment, create necrotic conditions for flora and fauna, and endanger human health. Therefore, the reemployment of these wastes is today an urgent need. In this work, a mud (QM) composed by quartz, feldspars, biotite and dolomite, is used for producing dense and foamed alkali-activated materials through an innovative and simple process, in which a mixture of mud and alkaline solution (plus foaming agent, when needed) is produced, cast in moulds and cured at 80 °C for 48 h. Another mineral powder (SRM), having a similar composition but carbonates-free, was also used, to prove the key role of alumino-silicates in producing dense alkali-activated materials, with excellent mechanical properties. Also, the foamed samples showed good mechanical properties, plus low thermal conductivity. These results demonstrate that alumino-silicate wastes could serve as source materials for producing materials suitable to be used for dense and cellular building elements, providing an effective alternative to mud disposal and related issues. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
10. Sealing efficiency of cement-based materials containing extruded cementitious capsules.
- Author
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Anglani, Giovanni, Van Mullem, Tim, Zhu, Xuejiao, Wang, Jianyun, Antonaci, Paola, De Belie, Nele, Tulliani, Jean-Marc, and Van Tittelboom, Kim
- Subjects
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HYDRAULICS , *SILICA gel , *WATER testing , *MATERIALS , *CONSTRUCTION materials , *WATER repellents - Abstract
• Extruded cementitious capsules are suitable to carry different healing agents. • Capsule waterproofing coating can be applied either internally or externally. • Active crack control allows to get a low crack width variability during pre-cracking. • The sealing efficiency is assessed via water flow and water absorption tests. • The sealing efficiency is up to 79% under water flow and 92% under water absorption. The intensive use of cement-based building materials is a growing concern in terms of environmental impact, since they significantly contribute to the global anthropogenic CO 2 emissions. The development of self-sealing cementitious materials could be a possible approach to improve the structural durability and thus reduce overall cost and environmental impact. In the present work, the efficiency of a self-sealing system using extruded cementitious capsules was experimentally investigated, and different healing agents were tested (specifically, a water-repellent agent, a polyurethane precursor and a solution of silica gel immobilized ureolytic bacteria). The self-sealing efficiency was evaluated in terms of capability to autonomously seal localized cracks induced in a controlled way. An active crack width control technique was adopted during the cracking procedure, in order to reduce the variation of the crack width within a series of specimens. Water permeability and capillary water absorption tests were performed to quantify the crack sealing ability, along with qualitative visual analysis of the crack faces. Positive results were achieved when using the water-repellent agent in water absorption tests, the bacterial agent in water-flow tests and the polyurethane precursor in both cases. This suggests that the proposed self-sealing system is sufficiently versatile to be used with different healing agents and that it can be effective in prolonging the material functionality by selecting the most appropriate agent for the real operating conditions. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
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