Fiber-reinforced syntactic foam composites prepared from polyglycidyl aromatic amine and polycarboxylic acid anhydride

DETAILED DESCRIPTION OF THE INVENTION In order to form the fiber-resin-microsphere composite of the present invention having the desired density and coefficient of thermal expansion, each of the three components must be selected so that the resulting combination thereof provides a mixture amenable to being cast into the desired configuration, as well as providing a final product having the required structural and physical properties.
Acceptable mixtures must have a viscosity that produces an accurate, voidfree casting with uniform material properties.
In addition, the proportion of fiber in the composite must provide the required thermal expansion, strength, and stiffness properties.
Further, the microsphere component must be chosen to provide the required low density in the composite.
Finally, each of the components must be capable of being combined with the other components and the effect of each on the other in the mixture thereof, as well as in the final composite must be taken into account.
In particular the properties of the composite are influenced by the properties, relative volume ratios, and interactions of the individual components.
More specifically, density, strength, stiffness (brittleness), coefficient of thermal expansion and processibility are strong functions of filler and fiber type, volume ratios and micropacking.
The following discussion provides a more detailed consideration of these various factors.
It should be noted that in the following discussion, the term "syntactic foam" is used herein to denote a filled polymer made by dispersing rigid, microscopic particles in a fluid polymer or resin and then curing the resin, as is known in the art.
The term "fiber-reinforced syntactic foam composite" is used herein to denote the cured product formed from the mixture of resin, microballoons, and reinforcing fibers in accordance with the present invention.
1.
Heat Curable Resin The heat curable, thermosetting resins used to prepare the syntactic foam composites of the present invention can be any heat curable thermosetting resin having appropriate viscosity for casting (e