US Patent 7037865 Composite materials

New composite materials having a high density of small particles, such as hollow microspheres, in a matrix material are disclosed. The microspheres are densely packed in the matrix material such that adjacent microspheres are positioned in contact with each other or very close together. Fiber flanking may be provided on the opposite sides of a layer of a core of composite material having the small particles and matrix material. Also disclosed are methods of making and using the composite materials.