The deformation and fracture behaviour of agarose biopolymer gels in tension and compression

摘要

In the present work, the deformation and failure behaviour of agarose gels (1 to 3 % (w/w)) has been assessed using both tension and compression test methods. Agarose gels typically were found to exhibit strain hardening, in both tension and compression, and the failure stresses were generally similar between the two test modes. Failure stress increased with biopolymer content, however the failure strains were essentially constant regardless of the agarose concentration (between 1 and 3 % (w/w)). The failure strains in compression were approximately twice those in tension. The small strain elastic moduli were ～3 times the shear moduli which, in combination with the failure strain behaviour, infers a Poisson ratio of ～0.5 (i.e. incompressible). It was apparent that agarose gels exhibit significant displacement (strain) rate hardening in compression. At the slowest displacement rates, strain hardening was not apparent, indicating that relaxation occurs within the gel structure during deformation (i.e. viscoelastic response). Weibull statistical analysis procedures were applied to the tension failure data for these agarose gels, and the initial results indicate that the strength distribution can be described as 'brittle', with Weibull modulus values similar to ceramics and glasses. The Weibull moduli values obtained were tentatively related to the types of flaw population present in the gels.