Elastica-based strain energy functions for soft biological tissue

Continuum strain energy functions are developed for soft biological tissues that possess long fibrillar components. The treatment is based on the model of an elastica, which is our fine scale model, and is homogenized in a simple fashion to obtain a continuum strain energy function. Notably, we avoid solving the full fourth-order, nonlinear, partial differential equation for the elastica by resorting to other assumptions, kinematic and energetic, on the response of the individual, elastica-like fibrils.Comment: To appear in J. Mech. Phys. Solid

Parameter estimation in a Holzapfel–Ogden law for healthy myocardium

A central problem in biomechanical studies of personalized human left ventricular (LV) modelling is to estimate material properties from in vivo clinical measurements. In this work we evaluate the passive myocardial mechanical properties inversely from the in vivo LV chamber pressure–volume and strain data. The LV myocardium is described using a structure-based orthotropic Holzapfel–Ogden constitutive law with eight parameters. In the first part of the paper we demonstrate how to use a multi-step non-linear least-squares optimization procedure to inversely estimate the parameters from the pressure–volume and strain data obtained from a synthetic LV model in diastole. In the second part, we show that to apply this procedure to clinical situations with limited in vivo data, additional constraints are required in the optimization procedure. Our study, based on three different healthy volunteers, demonstrates that the parameters of the Holzapfel–Ogden law could be extracted from pressure–volume and strain data with a suitable multi-step optimization procedure. Although the uniqueness of the solution cannot be addressed using our approaches, the material response is shown to be robustly determined

The effect of material and thickness of collector electrode on fiber fineness in electrospinning

AATCC;INDA;TAPPI;The Fiber Society2010 Spring Conference of the Fiber Society -- 12 May 2010 through 14 May 2010 -- Bursa -- 105817[No abstract available

Efficient Two-Scale Modeling of Finite Rubber Viscoelasticity

The paper is concerned with the constitutive modeling of finite viscoelasticity of rubbery polymers. Motivated by experimental observations, the overall free energy is additively decomposed into the elastic equilibrium and viscous non-equilibrium parts. The elastic response of the material is modeled by the recently proposed non-affine micro-sphere model, Miehe et al. (2004). The effective constitutive modeling of the superimposed viscous response is essentially one-dimensional and related to a space orientation of a chain associated with a local point on the micro-sphere (S2). The homogenization procedure is carried out through a direct numerical evaluation of averaging integrals. In contrast to our recent approach in Miehe and Göktepe (2005), the discrete distribution of the microscopic internal variable fields on S2 is approximated by the efficient storage in the form of a second-oder tensor that can be looked upon as a coefficient tensor of a truncated tensorial Fourier representation of a continuous field on S2. The modeling capacity of the proposed model is tested against experiments on HNBR50 specimes

Production and analysis of electrospun pa 6,6 and pva nanofibrous surfaces for filtration

Electrospun nanofibrous surfaces were produced by using two different polymers (PA 6,6 and PVA) at three different levels of polymer feeding rate (0.2, 0.6 and 1.0 ml/h, respectively) and three different levels of production time in electrospinning (5, 10 and 15 minutes, respectively) and the effect of polymer type, polymer feeding rate and production time was determined by analyzing unit weight and thickness of the nanofibrous membranes as well as fibre fineness and pore size distributions. The results showed that much finer fibres were produced by PA 6,6 polymer compare to PVA. The minimum average fibre fineness was 150.96 nm (by PA 6,6 polymer; 0.2 ml/h; 5 min.) while maximum fibre fineness was 243.43 nm (by PVA polymer; 0.6 ml/h; 15 min.). Similarly, the pore sizes of nanofibrous surfaces produced by PA 6,6 were smaller compare to the ones produced by PVA polymer. The results also indicated that coarser fibres were produced as the polymer feed rate and electrospinning time increased. In the second part of the work, composite structures were obtained by combining nanofibrous surfaces with PP non-woven material and their air permeability and filtration efficiency by using an aerosol having 0.2-0.33 mm diameter range were analyzed. The air permeability of PA 6,6 nanofibrous surfaces were much higher compare to the ones produced by PVA and quite high filtration efficiency (99.901 %) was obtained with PA 6,6 nanofibrous surfaces. Also, potential of these nanofibrous surfaces was evaluated by analysing chemical groups eliminated following their exposure to cigarette smoke which was chosen as a specific case study. © 2021 Inst. Nat. Cercetare-Dezvoltare Text. Pielarie. All rights reserved.NKUBAP.00.17, YL.13.05The authors would like to thank Tekirdağ Namık Kemal University, Scientific Research Project Unit as this work was supported by project number NKUBAP.00.17.YL.13.05. The authors also would like to thank 3M San. Tic. A. Ş. and Denge Kimya ve Tekstil San. Tic. A.Ş. (Tekirdağ, Turkey) for providing their facilities during some part of the tests