THE BURDENED AREA AS A STRUCTURAL INDICATOR OF INTERFACE BONDING STRENGTH

In laminate structures, the interface debonding failures usually resul t from very complex fracture mechanisms which lead to different streng thening approaches. The bonding strength of two dissimilar bodies depe nds, to a great extent, on the bulk materials and the bonding structur e in addition to the intrinsic interface adhesion. The structural effe ct on bonding strength will be emphasized in this investigation. The a nalysis will exhibit the relationship of materials, structures, and in terface adhesion which is essential in understanding the failure mecha nisms. This paper proposes that the burdened area on an interface is, according to experimental and analytical results, a structural indicat or for bonding strength. Such a comprehensive parameter makes it easy to determine the complex contributions of so many structural parameter s to the bonding strength, Although there are many microscopic observa tions of separated surfaces which support the concert of burdened area , a direct measurement of the burdened area is difficult in practice. Therefore an analytical or numerical evaluation is necessary. The solu tions from the classical equation of elastic plate will be used to det ermine the distribution of interface stress as well as the size of bur dened area. The bonding strength is considered as fracture toughness w hich is directly related with the burdened area. As a useful indicator for evaluating the bonding strength, the burdened area includes the e ffects of many structural parameters and mechanical properties, such a s: elastic modulus. Poisson's ratio, layer thickness, slanting angle, and corner radius. Burdened area is a property of structure because it is independent of the peeling loads, the material's yielding strength and interface adhesion. As far as energy release rate is concerned, t he boundary load is virtually distributed on the whole burdened area. The concept of burdened area will facilitate mechanical design of bond ing strength and lends to a better understanding of various debonding failures.