Failure of intercellular adhesion in hair fibers with regard to hair condition and strain conditions

Although adhesion failure in hair fibers can occur inside cells, it occurs more frequently in the cell membrane complex (CMC), often involving the rupture of interlayer bonds. Therefore, a model of the CMC presented, based on prior research, in which we propose interconnecting bonds between the layers to assist interpretation of hair‐fracturing mechanisms for cuticle chipping, deep transverse cuticle cracks, during heat drying, scale lifting by surfactants, and catastrophic failure. Failure in the wet state involves hydrophilic layers, e.g. the contact zone of the CMC or the endocuticle or bonding to hydrophilic layers, whereas failure in the dry state generally involves bonding between hydrophobic, e.g. beta‐delta failure. Chemical damage by perms, bleaches, and sunlight, by breaking specific bonds, influences the sites of initial failure and increases the number of routes for crack propagation, leading to more complex fracture patterns.