Fiber-matrix coupling

Fiber/matrix Coupling agent Tensile strength Increase in properties [%] Young s Compression modulus strength Impact energy... 

Figure 5.86 Fiber-matrix coupling in continuous, unidirectional fiber-reinforced composites (a) Coupling for tensile stress parallel to fiber axis, (b) Coupling for stress perpendicular to fiber axis. Reprinted, by permission, from N. G. McCrum, C. P. Buckley, and C. B. BucknaU, Principles of Polymer Engineering, 2nd ed., p. 258. Copyright 1997 by Oxford University Press.

The agave plant grown mainly in Mexico, used to make tequila and sweetener (and related to sisal), also supplies a waste fiber that has been used in PP at 55% loading. It is said to increase tensile modulus, and like other plant fibers, requires PP grafted with maleic anhydride for fiber/matrix coupling. 

It seems that composite failure is an elongation controlled process such that a high fiber elongation can increase the composite elongation for this ductile PP matrix (elongation of 40%). This view is in accord with the excellent fiber matrix coupling from Fig. 18.9 (right). 

Fig. 18.20 Possible mechanisms of fiber-matrix coupling through a reaction with hexamethylene diisocyanate...

WJ Cantwell, W Tato, HH Kausch, R Jacquemet. The influence of a fiber-matrix coupling agent on the properties of a glass/polypropylene GMT. J Thermoplastic Composite Materials 5 304-317, 1992. 

The improvements in fiber-matrix bonding brought about by the application of silane coupling agents should be reflected in the results of IFSS measurement using the SFC specimen. The relative merits of the three silanes studied here can thus be compared through the IFSS values obtained under optimal conditions of silane application in each case. These results are presented in Figs 6 and 7. 

Single fiber tests were used to evaluate the fiber-matrix adhesion. Acid/base interactions do play a role in this adhesion but are not exclusively responsible for improvements at the interface. Treatment with a siloxane coupling agent was proven to be effective in lowering the dispersive component of the carbon fibers and altering their acid/base properties, producing poorer adhesion. 

Methods of filler pretreatment lignin treated by methylolation decreases the rate of cure of phenolic adhesives " carbon fiber was anodicaUy oxidized and subjected to various treatments with coupling agents to improve interfacial interaction with phenolic resins and oxidative stability of carbon fibers titanate coupling of oxidized fibers resulted in improved adhesion to matrix and enhanced thermal stability of fibers ... 

Farlow and Hayward described the development of an automated air-coupled Lamb wave scanner for rapid inspection and imaging of defects in carbon fiber composites [142]. It can detect disbonding of the fiber-matrix interface, broken or missing fibers, and changes in elastic properties of the adherend, which may indicate a change in thickness (i.e., a void) [14]. 

The fundamental basis of nanosciences is the creation of nanoobjects as well as the study of their properties. Superimposed, moreover, is knowledge allowing the transformation of nanoobjects into material. This corresponds to the discovery and the development of specific assembly and organization methods. It is also necessary that these methods be able to allow the production of devices in the form of films, fibers, matrixes, composites or even porosity-controlled solids. The materials thus created must present precise and useable physical, mechanical or chemical properties. In the case of smart materials these properties must be organized each in relation to the others and coupled between them in an interactively controlled manner. 

---