Debonding angle

From the debonding angle and the local draw ratio, it was possible to calculate a void content in the drawn blend. Subsequently, a density could be calculated for comparison with the measured density. Assuming that the void is conical in shape with a base area (Acone) given by... 

Figure 5. Effect of debonding angle (6) on the calculated yield stress from equation 8. Data for LLDPE-PS blends are included as open circles.

The blister test has several advantages. It does not need any mechanical grip to the film to initiate a debonding. The uniformly distributed axisymmetric debonding angle close to the circular crack tip is smaller than with any other mechanical test. Thus the blister test minimizes the energy dissipation more effectively than any other test method. 

Figure 26. Schematic representation of a deformed shell, S, of matrix stress,o. Partial dewetting occurs with a debonding angle...

The stress distribution analysis shows that maximum stress concentration develops in the radial direction at the pole of the particle, and shear yielding is initiated at around 45° on the surface of rigid particles. Debonding occurs at the pole of the particle, and extends to a critical angle [27]. In case of total adhesion, debonding does not occur and there is cavitation in the matrix, at some distance from the particle pole (not at the interface). 

Short fibre composites, fibre orientation, fracture toughness, fracture mechanisms, fibre pullout, fibre debonding, critical fibre angle. 

This sharp variation in toughness has been interpreted as a transition between different fracture mechanisms. Matrix fracture and fibre debonding are the prevailing fracture mechanisms at low values of the fibre orientation factor, while at high values the main fracture mechanism is fibre pull-out. Thus, besides a critical fibre length, also a critical fibre angle should be considered. 

The yield stress taken from the stress-strain curves is compared with predictions in Figure 7. The upper bound is the prediction from equation 5 for a yielding angle of 70° and Hashing upper modulus bound. The lower bound in Figure 7 is obtained from Nielsen s approach for completely debonded parti-... 

Figure 7. Yield stress of the compatibilized blends compared with calculations. Key —, a yielding angle of 70° and Hashins upper modulus bound —, Nielsens approach for debonded particles and, Nielsens approach with a debond-...

FIGURE 39.15 Schematic of the peel test, and associated mode-mixity phase angle for the case of a flexible film on a rigid substrate mode II arises from bending near the debond edge. 

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