Silicone elastomers have attracted considerable attention due to their wide range of applications in biomedical engineering and soft robotics. In this thesis work, an extensive thermo-mechanical characterization of Ecoflex Shore hardness 00-50, a commercially available silicone elastomer, has been carried out. The mechanical behaviour of the material has been characterized performing monotonic and cyclic loading tests, in different states of deformation, i.e. uniaxial tension, pure shear and biaxial tension, at different strain rates and different temperatures. Experimental findings allowed to highlight a time-dependent response of the material and to quantify the contribution of dissipative deformation phenomena to the overall strain energy. The applicability of constitutive equations proposed in literature to model the mechanical behaviour of similar silicone elastomers was verified for the material under study: the monotonic loading behaviour can be properly described for strains lower than 400% in uniaxial tension and pure shear, and up to failure in biaxial tension. The effect of temperature on the mechanical response and, in particular on ultimate stress and strain, has been studied in the range between -40°C and 140°C. Results showed that the material mechanical behaviour is sensitive to temperature, and in particular a decrease of ultimate stress and strain has been observed with increasing temperature. Finally, the data obtained at the various temperatures and strain rates has been used to define a failure envelope, a concept already proposed in literature for other elastomers and useful to predict the material ultimate stress and strain in any loading condition.
Gli elastomeri siliconici attraggono sempre maggiore interesse in relazione al loro impiego in campo biomedicale e nella "soft robotics". In questo lavoro di tesi, è stata effettuata un'ampia caratterizzazione termo-meccanica del materiale Ecoflex con durezza Shore 00-50, disponibile in commercio. Il comportamento meccanico del materiale è stato caratterizzato attraverso prove di carico monotono e ciclico, in diversi stati di deformazione, ovvero trazione uniassiale, puro taglio e trazione biassiale, a differenti velocità di deformazione e diverse temperature. I risultati sperimentali hanno messo in risalto la dipendenza dal tempo della risposta del materiale ed hanno permesso di quantificare il contributo legato a fenomeni dissipativi dell'energia di deformazione. L'applicabilità di equazioni costitutive, proposte in letteratura per modellare il comportamento meccanico di elastomeri simili, è stata verificata per il materiale considerato: il comportamento a carico monotono viene descritto correttamente fino a deformazioni del 400% in trazione uniassiale e puro taglio, e fino a rottura in trazione biassiale. L'effetto della temperatura sulla risposta meccanica e, in particolare, su sforzo e deformazione a rottura del materiale, è stato studiato nell'intervallo da -40°C a 140°C. I risultati mostrano che il comportamento meccanico del materiale è sensibile alla temperatura, ed in particolare si osserva una progressiva diminuzione di sforzo e deformazione a rottura all'aumentare della temperatura. Infine, i dati ottenuti a varie temperature e velocità di deformazione sono stati utilizzati per definire una "failure envelope", concetto già proposto in letteratura per altri elastomeri e usato per prevedere sforzo e deformazione a rottura in una qualsiasi condizione di sollecitazione.
A study on the mechanical behaviour of Ecoflex 00-50 silicone elastomer
Lavazza, Jacopo
2020/2021
Abstract
Silicone elastomers have attracted considerable attention due to their wide range of applications in biomedical engineering and soft robotics. In this thesis work, an extensive thermo-mechanical characterization of Ecoflex Shore hardness 00-50, a commercially available silicone elastomer, has been carried out. The mechanical behaviour of the material has been characterized performing monotonic and cyclic loading tests, in different states of deformation, i.e. uniaxial tension, pure shear and biaxial tension, at different strain rates and different temperatures. Experimental findings allowed to highlight a time-dependent response of the material and to quantify the contribution of dissipative deformation phenomena to the overall strain energy. The applicability of constitutive equations proposed in literature to model the mechanical behaviour of similar silicone elastomers was verified for the material under study: the monotonic loading behaviour can be properly described for strains lower than 400% in uniaxial tension and pure shear, and up to failure in biaxial tension. The effect of temperature on the mechanical response and, in particular on ultimate stress and strain, has been studied in the range between -40°C and 140°C. Results showed that the material mechanical behaviour is sensitive to temperature, and in particular a decrease of ultimate stress and strain has been observed with increasing temperature. Finally, the data obtained at the various temperatures and strain rates has been used to define a failure envelope, a concept already proposed in literature for other elastomers and useful to predict the material ultimate stress and strain in any loading condition.File | Dimensione | Formato | |
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Thesis_Lavazza.pdf
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Descrizione: Master Thesis
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Executive_Summary_Lavazza.pdf
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Descrizione: Executive Summary
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https://hdl.handle.net/10589/187294