Uniaxial Compression of Bonded and Lubricated Gels

Experimental measurements of the response of starch gels in uniaxial compression, under both lubricated and bonded conditions, are reported. With samples of initial height h0 it was found for lubricated compression that true stress σ versus strain plots (strain being defined as e=(h0−h)/h) were independent of h0. The curves of true stress versus strain, for uniaxial compression of gels bonded to the instrument platens, lay well above the curve obtained in lubricated compression; and furthermore, the results in bonded compression were strongly dependent on h0. To a good approximation the results in bonded compression could be brought into agreement with the lubricated compression data by correcting true stress for bonded compression by a factor (1+R02/2h2)−1, a modification of a result originally reported by Gent and Lindley. The corrected curves for bonded compression were independent of h0 and agreed with the response of the lubricated samples until near the failure point. Corrected stress for bonded com...