Through-tiiickness Elastic Constant for Aramid-epoxy/aluminum Composite Materials*

The objectives in this study were to deterrnine the through-thickness elastic constant of fiber-epoxy/metal composites with ultrasonic measurements and determine the elastic constants of the constituent layers. The specimens that we studied consist of alternaring layers of aluminum (2024 TI) and fiber-epoxy [1], all of which are 200 to 300 jlm thick. As Figure 1 indicates the outer two layers of the composite are aluminum, so that there is always one additionallayer of aluminum in the composite. The fiber-epoxy layers consist of a unidirectionallayup of ararnid fibers for the ararnid-epoxy/aluminum specimens. For the glass-epoxy/aluminum specimen, the fiber-epoxy layers consist of two sublayers of unidirectional fibers where the fibers of one sublayer lie at 90° with respect to the other sublayer. Because the fibers of both sublayers are perpendicular to the transmitting transducer, the ultrasound perceives the two sublayers as a single layer.