A new development of the strain energy function for hyperelastic materials using a logarithmic strain approach

The development of a new strain energy function for hyperelastic solids based on the logarithmic strain measure is the objective of the present article. For all possible types of deformation it was shown that the proposed energy function is based on three independent material parameters. Using available experimental data for rubber‐like materials from the literature, one may determined the materials parameters by a nonlinear fitting. The available domain of the strain energy function can be determined by plotting the third invariant of logarithmic strain vs the second one. The numerical integration of the experimental data of true stress as a function of the logarithmic strain for various types of deformation yields the strain energy function W, for rubber‐like solids. The proposed model involves only one parameter that must be determined by fitting with the experimental data. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 660–672, 2000     

Applying fractography and fracture mechanics to the energy and mass of crack growth for glass in the mirror region

The mirror region following the fracture initiation site is considered by applying fracture mechanics principles along with experimental observations of the crack velocity at the formation of the mirror mist boundary. Several issues regarding this crack growth in glass are addressed after considering the terminal velocity of crack growth and the mirror mist boundary information on silicate glasses. A strain energy release rate criterion is applied to estimate the kinetic energy of an advancing crack in glass at the mirror/mist boundary. This energy is then utilized to estimate the effective mass of the crack at the mirror/mist boundary. It is compared with material volumes in the vicinity of the crack.     

Effects of the structural components on slow crack growth process in polyethylene blends. Composition intervals prediction for pipe applications

A linear low density polyethylene (LLDPE) obtained from a metallocene based catalyst, was blended in an extruder with a high density polyethylene (HDPE) homopolymer synthesized with an iron based catalyst. The bimodal polyethylenes, made with blends from 0 to 100 wt % of copolymer were characterized by SEC, DSC, ESEM, SEC‐FTIR, and TREF, while their resistance to the slow crack growth (SCG) was evaluated through the PENT test. Results provide that polymer blends with copolymer contents between 47.5 and 72.5 wt % are suitable for pipe applications. Furthermore, a method based on the intercrystalline tie chains calculus is proposed as suitable and attractive, because of its simplicity and novelty, to forecast long term performance and to predict capabilities. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011