Matrix cohesive shear strength

Cohesive failure of the adherend takes place when the adherend fails due to loads in excess of the adherend strength. In laminate structures the failure typically initiates from the matrix between the laminae as a result of out-of-plane loads or interlaminar shear loads. Other types of failure initiation are also possible, especially for FRP composites that do not have a layered structure. 

If the interfacial bonding strength of the composite material is less than the cohesive strength of the matrix resin and the strength of the filler, a stress concentration near the filler can easily occur when composite materials are subjected to shear or tensile stress. Debonding damage will occur near the interface if the interfacial bonding is weak. 

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