How can adhesion be determined from micromechanical tests?

The concept of adhesional pressure was proposed to characterise the interfa cial bond strength in fibre-matrix systems. The adhesional pressure is the interfacial normal stress produced by the molecular interaction between the fibre surface and the matrix. Using the variational mechanics approach. we calculated the critical normal stress, at which debonding starts in the pu ll-out and microbond tests. This critical value can be used as a failure cr iterion. The relationship between "fundamental" (WA) and "practical" (adhes ional pressure) adhesion was investigated. The adhesional pressure appeared to linearly depend on the work of adhesion from the IGC data. This allows to estimate W-A from destructive micromechanical tests. An important advant age of the proposed approach is that it can characterise adhesion for real conditions of the composite formation, including irreversible adhesion. (C) 2001 Elsevier Science Ltd. All rights reserved.