Hybrid composite panels with fireproof lightweight core and carbon fiber skin

Structural sandwiches are a special form of laminated composite in which thin, strong, stiff, hard, but relatively heavy facings are combined with thick, relatively soft, light and weaker cores to provide a lightweight composite stronger and stiffer in most respects than the sum of the individual stiffness and strengths. In this investigation lightweight core with a density of about 700 kg/m³ were made using ceramic spheres and an inorganic matrix, called polysialate. These cores have a compressive strength of about 5 MPa. Thin slabs of these cores were externally reinforced with carbon fabric to obtain hybrid composite panels. The panels were tested under three point bending using deflection control. The primary test variables were the amount of carbon reinforcement and the behavior after exposure to temperatures of 200, 400 and 600°C. Behavior of panels reinforced with Nicalon fibers are compared with the panels reinforced with carbon fibers. The results indicate that the system is viable to fabricate lightweight, fireproof structural panels. Delamination of fabrics did not occur in any of the samples. Classical bending theory provides a reasonable prediction of load-deflection behavior.