Tension Separation
Tensile separation of crack faces perpendicular to the plane of the failure represents the most common mechanism of structural rupture in fibrous materials. This behavior, termed mode I fracture, describes the opening mode where an applied tensile load drives a crack straight through the paperboard or adhesive joint. It is a critical parameter in assessing the durability of glued joints in heavy-duty packaging.
Delamination Energy
Propagation of the failure depends on the energy release rate required to create new crack surfaces within the paperboard matrix. In a mode I fracture, the strength of the fiber-to-fiber bonds and the distribution of adhesive across the joint determine the resistance to crack growth. Testing involves peeling or pulling specimens apart to measure the critical strain energy release rate.
High values indicate that the board can absorb substantial energy before catastrophic failure occurs, which is necessary for boxes subject to rough handling or dropping.
Joint Durability
Sealed flaps on corrugated containers depend on high resistance to opening forces during transport. When board or adhesive exhibits low resistance to mode I fracture, cartons can pop open under the pressure of the packed contents. Selecting the correct glue viscosity and compression time prevents this defect.
