Journal of The Mechanical Behavior of Biomedical Materials, Mar 1, 2021
An effective description of the mechanical behavior of biodegradable copolymers suture threads re... more An effective description of the mechanical behavior of biodegradable copolymers suture threads requires the analysis of their response under cyclic loading and the prediction of the fundamental damage and residual stretches effects. In this paper we propose a micromechanically-based model adopting a new form of Worm Like Chain free energy for the copolymer chains, which takes care of the insurgence of residual stretches on the basis of a rigorous statistical mechanics result. Under the affinity hypothesis we subsequently derive the macroscopic response of the material. The obtained model has a clear physical interpretation and depends on a small number of parameters, which can be fitted by a simple uniaxial test. The effectiveness of the theoretical results has then been verified by performing cyclic tests on Monocryl® monofilament sutures and showing the ability of the model in predicting with high accuracy the history dependence, the damage and permanent deformations in the obtained response.
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
We study a prototypical system describing instability effects due to geometric constraints in the... more We study a prototypical system describing instability effects due to geometric constraints in the framework of nonlinear elasticity. By considering the equilibrium configurations of an elastic ring constrained inside a rigid circle with smaller radius, we analytically determine different possible shapes, reproducing well-known physical phenomena. As we show, both single- (with different complexity) and multi-blister configurations can be observed, but the lowest energy always corresponds to single-blister solutions. Important physical insight is attained through an analogy between the elastica and the dynamics of a nonlinear pendulum. A complete geometric characterization is attained, proving symmetry and other relevant properties. The effectiveness of the model is tested against a simple experiment by considering a thin polymer strip constrained in a rigid cylinder.
We propose paradigmatic examples to show how material damage effects can be described as a solid-... more We propose paradigmatic examples to show how material damage effects can be described as a solid-solid phase transition. Start- ing from the pioneering work of J.L. Ericksen [8] and the extensions of R.L. Fosdick to three-dimensional non linear elasticity, we describe the insurgence of damage as a transition between two material states (dam- age and undamaged) characterized by two different energy wells. We consider the two separate constitutive assumptions of a simple damage- able Neo-Hookean material and a more complex microstructure inspired Gent material with variable limit threshold of the first invariant. In both cases we study two different deformation shear classes, one homogeneous and the other one inhomogeneous and obtain fully analytic description of the system damage response under cyclic loading. While the assumption of two only (damaged and undamaged) configurations is simplistic, the model can be extended to systems with more energy wells with varaible degrees of damage.
We propose a microstructure inspired approach for rubberlike materials. These materials are model... more We propose a microstructure inspired approach for rubberlike materials. These materials are modeled as a mixture of an elastic matrix and a damageable fraction, assigned by a distribution of links with variable activation and rupture thresholds. In particular, the hysteretic behavior is described by considering the recross-linking effect under unloading. Based on the physical interpretation of the material distribution and parameters of the model proposed here, we are able to obtain an effective and numerically efficient three-dimensional, nonlinear damage and hysteresis model for rubberlike solids. To demonstrate the feasibility of this model in reproducing complex deformation histories, we performed cyclic uniaxial and shear tests on ethylene-propylene diene monomer specimens. A comparison with diffusely adopted models clearly demonstrates the advantages of the proposed approach. In particular, we show the possibility, crucial for real applications, of describing a completely diff...
Journal of The Mechanical Behavior of Biomedical Materials, Mar 1, 2021
An effective description of the mechanical behavior of biodegradable copolymers suture threads re... more An effective description of the mechanical behavior of biodegradable copolymers suture threads requires the analysis of their response under cyclic loading and the prediction of the fundamental damage and residual stretches effects. In this paper we propose a micromechanically-based model adopting a new form of Worm Like Chain free energy for the copolymer chains, which takes care of the insurgence of residual stretches on the basis of a rigorous statistical mechanics result. Under the affinity hypothesis we subsequently derive the macroscopic response of the material. The obtained model has a clear physical interpretation and depends on a small number of parameters, which can be fitted by a simple uniaxial test. The effectiveness of the theoretical results has then been verified by performing cyclic tests on Monocryl® monofilament sutures and showing the ability of the model in predicting with high accuracy the history dependence, the damage and permanent deformations in the obtained response.
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
We study a prototypical system describing instability effects due to geometric constraints in the... more We study a prototypical system describing instability effects due to geometric constraints in the framework of nonlinear elasticity. By considering the equilibrium configurations of an elastic ring constrained inside a rigid circle with smaller radius, we analytically determine different possible shapes, reproducing well-known physical phenomena. As we show, both single- (with different complexity) and multi-blister configurations can be observed, but the lowest energy always corresponds to single-blister solutions. Important physical insight is attained through an analogy between the elastica and the dynamics of a nonlinear pendulum. A complete geometric characterization is attained, proving symmetry and other relevant properties. The effectiveness of the model is tested against a simple experiment by considering a thin polymer strip constrained in a rigid cylinder.
We propose paradigmatic examples to show how material damage effects can be described as a solid-... more We propose paradigmatic examples to show how material damage effects can be described as a solid-solid phase transition. Start- ing from the pioneering work of J.L. Ericksen [8] and the extensions of R.L. Fosdick to three-dimensional non linear elasticity, we describe the insurgence of damage as a transition between two material states (dam- age and undamaged) characterized by two different energy wells. We consider the two separate constitutive assumptions of a simple damage- able Neo-Hookean material and a more complex microstructure inspired Gent material with variable limit threshold of the first invariant. In both cases we study two different deformation shear classes, one homogeneous and the other one inhomogeneous and obtain fully analytic description of the system damage response under cyclic loading. While the assumption of two only (damaged and undamaged) configurations is simplistic, the model can be extended to systems with more energy wells with varaible degrees of damage.
We propose a microstructure inspired approach for rubberlike materials. These materials are model... more We propose a microstructure inspired approach for rubberlike materials. These materials are modeled as a mixture of an elastic matrix and a damageable fraction, assigned by a distribution of links with variable activation and rupture thresholds. In particular, the hysteretic behavior is described by considering the recross-linking effect under unloading. Based on the physical interpretation of the material distribution and parameters of the model proposed here, we are able to obtain an effective and numerically efficient three-dimensional, nonlinear damage and hysteresis model for rubberlike solids. To demonstrate the feasibility of this model in reproducing complex deformation histories, we performed cyclic uniaxial and shear tests on ethylene-propylene diene monomer specimens. A comparison with diffusely adopted models clearly demonstrates the advantages of the proposed approach. In particular, we show the possibility, crucial for real applications, of describing a completely diff...
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Papers by Giuseppe puglisi