How can adhesion be determined from micromechanical tests?

Interfacial bonding of Flax fibre/Poly(l-lactide) bio-composites

“…which the fibre enters the droplet. s ult represents a limit to s app when the debonded droplet length tends to 0 [37]. It includes the development of residual thermal stresses (a and DT).…”

Adhesional pressure as a criterion for interfacial failure in fibrous microcomposites and its determination using a microbond test

“…It can be seen that shear stress is zero at the point where the fiber enters the matrix (maximum s rz is reached in the vicinity of this point but at z 5 0), while radial stress, r rr , is at its maximum here. Pisanova et al [40] assumed that interfacial crack is initiated when r rr reaches its critical value, r d , at z = 0, and proposed r d as a new stress-based criterion for interfacial failure. At the moment of crack initiation, the radial tensile stress, r rr , balances the adhesional pressure (interfacial pressure produced by adhesion forces), and therefore r d is numerically equal to this adhesional pressure and directly proportional to the work of adhesion, W A .…”

“…Indeed, it accounts for both non-local (long-range) molecular interactions at the interface, such as van der Waals forces, and local interfacial bonds (acid-base interactions) [38][39][40]. The molecular kinetics theory shows that the intensity of these interactions, in particular, the number of local bonds per unit interfacial area, depends on the conditions of the contact formation [41,42].…”

“…[7,33,40], we proposed to consider the ''adhesional pressure'', or the ultimate normal (radial) component of interfacial stress in fiber-matrix systems, r d , as a new stress-based failure criterion and a tool for estimating the work of adhesion between a fiber and a matrix (including the contribution of chemical interactions). The introduction of this criterion can be justified by the fact that, as has been demonstrated by Scheer and Nairn [55], Piggott [60] and Marotzke [61], crack initiation in the microbond test occurs in Mode I (normal tension); therefore, it was quite natural to suppose that interfacial debonding starts when normal stress at some point at the interface reaches its ultimate value, namely, adhesional pressure (r d ).…”

Investigation of fiber/matrix adhesion: test speed and specimen shape effects in the cylinder test

“…Therefore the knowledge of the fiber/matrix adhesion is essential for the calculation of mechanical properties of composites during the design phase [1][2][3][4][5]. The interfacial shear strength as a characteristic of adhesion can be determined by different micromechanical (or single fiber) tests among which the microdebond method is usually preferred [6][7][8][9][10][11]. The cylinder test, developed by us (see Fig.…”