Mechanical and fracture properties for predicting cracking in semi‐sweet biscuits

Abstract

SummaryMechanical and fracture properties required for predicting crack development in semi‐sweet (‘rich tea’) biscuits have been experimentally determined. Pilot‐scale biscuits of different fat concentrations were prepared and studied with commercial biscuits at different moisture contents. Bending modulus, fracture stress and strain were measured using three‐point bending tests. All biscuit types showed considerable dependence on moisture content over a range of 4–12%. Young's modulus and failure stress showed a uniform decrease and failure strain showed an increase with increasing moisture content. For pilot‐scale biscuits of different fat concentrations, an increase in fat level caused a decrease in modulus and failure stress values; however, the failure strains were very similar for all the fat types. The testing of the samples with top surface up and top surface down revealed that the sample orientation does not affect the measured parameters. The measured parameters also did not show any directional dependence within the plane, thus assuring that the assumption of an isotropic material would be valid for modelling. The mechanical and fracture properties measured in this study will serve as a very useful set of data to predict the stress state and cracking of the checked biscuits.