Application of an Astroquartz Material System to Composite Sandwich Structure

This report presents information regarding research conducted at the Helicopters Division of Boeing Defense & Space Group concerning an Astroquartz-based material system in sandwich structure designed for rotorcraft primary airframe structure. The purpose of this work was threefold: 1) to evaluate the mechanical properties of Astroquartz sandwich elements, 2) to evaluate the impact resistance and damage tolerance of Astroquartz-facesheet sandwich laminates, and 3) to compare these results to Kevlar-facesheet sandwich laminates. In tension, Astroquartz was less stiff than Kevlar 49 but had a significantly higher tensile stress at failure. In compression, Astroquartz was nearly linear-to-failure, as opposed to Kevlar. Undamaged compression specimens failed due to face wrinkling at stress levels higher than conventional Kevlar-fabric sandwich specimens. Similarly, residual strength after damage was also higher than Kevlar-fabric results. ETW tests showed little reduction in strength due to environment. Finally the Astroquartz showed a significant reduction in dielectric constant compared to Kevlar, an important consideration for L/O applications.