Fracture properties of potato crisps

The Weibull modulus of potato crisps is about 4, comparable with ceramic materials, with a characteristic strength of about 1.5 MPa. This combination of brittleness and weakness gives crispness. The critical stress intensity factor (K-IC) and the energy of fracture (R) are around 0.12 MPa root m and 45 J m(-2), respectively. There was no significant difference between the material values obtained for the fracture properties of crisps of a range of subjective 'crispness' as measured by a trained organoleptic panel. Crispness is ranked by the structural bending strength. Centrally loaded plate tests give qualitative evaluation of crispness. Both these tests could be used in quality control, with advantage over organoleptic tests such as cost, the time required, objectivity, consistency of results, the relation of the measured parameters to standard materials tests and the relatively small amount of material that is needed by comparison.