Autohesion bond strength

Figure 7.22 Schematic diagram of autohesive bond strength development across an interface...

The interply bond strength for thermoplastic matrix composites has been shown to be dependent upon the processing parameters, pressure, temperature, and contact time. If the temperature distribution in the composite is nonuniform during processing, the ply interfaces will bond (or heal) at different rates. Thus, for a specified processing cycle, it is important to know precisely the temperature and degree of autohesive bonding at every point in the composite laminate in order to estimate the required process time. 

Consolidation and development of interlaminar bond strength for thermoplastic matrix composites have been modeled by two mechanisms intimate contact and autohesion. Intimate contact describes the process by which two irregular ply surfaces become smooth (Fig. 13.10). In areas in which the ply surfaces are in contact, autohesion occurs, and the long thermoplastic polymer chains diffuse across the ply boundaries. Filament winding with thermoplastic matrix materials is considered an on-line consolidation process in that local... 

The theory of adhesion by diffusion was espoused by various Russian scientists, the most prominent of whom was Voyutskii, who wrote a monograph on the subject. The theory was given a quantitative theoretical basis by the work of Vasenin, who derived the relationship for bond strength in autohesion shown in Eq. (108). 

The bond strength of the particles in the original mass, i.e., the autohesion, also determines the packing density of the powder mass and its sintering properties. The packing density is given by the shrinkage of the powder. 

Effect of corona treatment on adhesion of polyethylene to itself (autohesion) has been studied as a function of lamination temperature and density, as shown in Figs 5.6 and 5.7. Corona treatment has a dramatic effect on the increase of adhesion bond strength over that achieved with untreated polyethylene. Increase in lamination temperature enhances the bond strength of treated film. 

The self-adhesion (autohesion) of polymers is of considerable practical importance as many moulding operations involve the need for streams of merging polymer melt to self-adhere to form a strong bond necessary to the integrity of the moulded article. Mechanisms of polymer diffusion are discussed in Polymer diffusion reptation and interdigitation and theories that relate interfacial structure to strength in Polymer-polymer adhesion models. In the latter article, the vector percolation (VP) model was described, which is here applied to welding, and the practical consequences of its predictions are drawn out. - ... 

The level of autohesion between blend PC/PET components can be estimated with the aid of shear strength of autohesional bonding which is given within the frameworks of generalized fiactal model as follows ... 

---