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In this article, we demonstrate the application of digital image correlation (DIC) in evaluating the strains and Poisson ratio of a range of soft materials in terms of their spatial and temporal resolutions. Four samples of Polydimethylsiloxane (PDMS) were used as control substances and were measured to have Poisson ratios of 0.498, 0.503, 0.500, and 0.499, in agreement with the reported incompressible value of 0.50 [1]. Two carbon nanotube (CNT) elastomers of identical composition, but one of a homogeneous and the other of an inhomogeneous CNT distribution, were used to determine the spatial resolution with good results (Fig. 2 and Fig. 4). The relaxation of a 3D polydomain liquid crystal elastomer (3D-LCE), a cholesteric liquid crystal elastomer (CLCE), and a polyacrylamide gel (PAAm) in water, were used to determine the temporal resolution. A 10min video short at 25fps was used to evaluate the time dependence of the 3D-LCE over which time an increase in the Poisson ratio was observed. The 3D-LCE relaxes from its initial state at 0.42 to 0.50, converging towards incompressibility. The CLCE was found to have a similar initial value of 0.44 but converged to ∼ 0.60, a consequence of its anisotropic nature. PAAm gel relaxation in water was studied over a time period of 7 hours with digital images taken periodically every minute. Its Poisson ratio was found to decrease smoothly from 0.50 to 0.26, with an accompanying reduction in force. The equilibrium result compares well to the 0.25 value predicted by theories of the strain induced swelling of dilute gels. In summary, we find DIC to be a powerful and easy to implement method of accurately measuring local strains in a range of soft materials.

At sufficiently large proton energies, Glauber multiple-scattering theory offers good opportunities for describing the final state interactions in electro-induced proton emission off nuclear targets. A fully unfactorized relativistic formulation of Glauber multiple-scattering theory is presented. The effect of truncating the Glauber multiple-scattering series is discussed. Relativistic effects in the description of the final-state interactions are found not to exceed the few percent level. Also the frequently adopted approximation of replacing the wave functions for the individual scattering nucleons by some average density, is observed to have a minor impact on the results when obtained in the independent-particle model. Predictions for the separated 4 He(e, e p) response functions are given in quasi-elastic kinematics and a domain corresponding with 1 Q 2 2 (GeV) 2 .