Interface Force
Mechanical interface strain forces calculated across multi-layer composite structures quantify interfacial adhesion demands under external bending loads. Inter-layer shear stress represents the tangential mechanical force per unit area acting along the boundary separating adjacent material layers in coated optical fibers or composite laminates.
Delamination Mechanism
Coated optical fibers subjected to dynamic cyclic bending experience shear force concentration along the primary-secondary acrylate interface. When inter-layer shear stress exceeds the chemical bond strength between polymer coatings, localized interfacial delamination occurs. Delaminated interfaces allow moisture aggregation, accelerating mechanical degradation of the protective coating.
Thermal cycling accentuates shear stress owing to mismatched thermal expansion coefficients between glass and surrounding polymers.
Strain Transfer
Surface-mounted optical fiber strain sensors depend on continuous shear strain transfer through protective coatings to the glass core. Inadequate interfacial bond strength reduces strain transfer efficiency, leading to measurement strain underreporting.
Qualification Boundary
Mechanical qualification protocols evaluate adhesive shear strength using short-beam shear tests specified in ASTM D2344 standards. Inter-layer shear stress failure limits set the boundary for maximum allowable strain cycles in structural health monitoring installations. Sourcing specifications mandate passing delamination-free thermal cycling protocols prior to sensor integration.
Optical strain sensors failing shear bond criteria exhibit baseline calibration drift and hysteresis.
