Multilayer radome structure and its fabrication

A method for preparing a multilayer article, the method comprising the steps of:

• shaping a first layer of a composite prepreg material comprising fibers embedded in a matrix comprising an oligomeric cyanate ester prepolymer and a finely divided thickening agent to an interior portion of a female mold;
• shaping a second layer of a syntactic material comprising a plurality of hollow microballoons embedded in a pre-polymer matrix to the material of the first layer;
• shaping a third layer of a composite prepreg material comprising fibers embedded in a matrix comprising an oligomeric cyanate ester prepolymer and a finely divided thickening agent to the material of the first layer;
• compacting the assembly of layers in the female mold;
• and
• heating the assembly of layers, simultaneous with said compacting step, to a temperature sufficient to cure the pre-polymeric material in the assembly and form a multilayer article.

A method for preparing a multilayer shell, the method comprising the steps of:

• providing a female mold having an interior whose shape corresponds to an exterior shape of the shell;
• providing a first layer of a composite prepreg material comprising fibers embedded in a matrix comprising a prepolymeric material having an apparent glass-transition temperature of from about 40.degree. F. to about 60.degree. F., a viscosity of greater than 10.sup.6 centipoise at ambient temperature, and a viscosity versus temperature profile which minimizes at a low value of about 100 centipoise at a temperature of about 300.degree. F. when continuously heated at a constant rate of about 18.degree. F. per minute from ambient temperature, and a finely divided thickening agent;
• shaping the material of the first layer to the interior of the female mold at a sufficiently slow rate that the material of the first layer is deformable;
• providing a second layer of a syntactic material comprising a plurality of hollow microballoons embedded in a matrix comprising a pre-polymeric material;
• shaping the material of the second layer to the material of the first layer shaped to the interior of the female mold;
• providing a third layer of a composite prepreg material comprising fibers embedded in a matrix comprising a prepolymeric material having an apparent glass-transition temperature of from about 40.degree. F. to about 60.degree. F., a high viscosity of greater than 10.sup.6 centipoise at ambient temperature, and a viscosity versus temperature profile which minimizes at a low value of about 100 centipoise at a temperature of about 300.degree. F. when continuously heated at a constant rate of about 18.degree. F. per minute from ambient temperature, and a finely divided thickening agent;
• and
• shaping the material of the third layer to the material of the second layer at a sufficiently slow rate that the material of the third layer is deformable.