Where does crazing collide?

In polymer physics, crazing is a localised deformation in glassy thermoplastics in which tensile stress opens a thin planar zone spanned by oriented, load-bearing polymer fibrils separated by elongated voids. Unlike a true crack, a craze still carries stress across its faces, so crazing both absorbs energy and acts as the precursor from which fracture cracks eventually grow. Kambour's A review of crazing and fracture in thermoplastics is the foundational survey of how craze zones initiate, draw fibrils, and break down into cracks in materials such as polystyrene and PMMA. The referent is a microstructural failure mechanism in a solid polymer, distinct from the surface cracking of a ceramic glaze that carries the same name.[1]

Unit

Craze initiation stress and fibril-spanned zone thickness

Recovery means

Not applicable

Measured by

Studied by the stress and strain at craze onset, fibril volume fraction and zone thickness, and the craze-to-crack transition under load

In ceramics, crazing is a glaze fault: a network of fine cracks that appears over a fired glaze when the glaze and the clay body beneath it contract by different amounts on cooling, leaving the glaze in tension it cannot bear. Because the cracks can admit water and weaken the surface, potters treat crazing as a defect and correct it by adjusting the glaze's thermal expansion or the fit between glaze and body. Hamer and Hamer's The potter's dictionary of materials and techniques describes the thermal-expansion mismatch behind it and the remedies for it. The referent is surface cracking of a brittle glassy coating driven by expansion mismatch, which is a different phenomenon from the fibril-spanned craze zones that form inside a stressed polymer.[2]

Unit

Crack spacing and pattern across the glazed surface

Recovery means

Not applicable

Measured by

Judged by the onset, spacing, and density of the crack network and by the expansion mismatch between glaze and body