Strength Retention and Corrosion Resistance of Graphite/Epoxy-Aluminum Honeycomb Sandwiches in Salt Spray and High Humidity Environments

摘要

Honeycomb sandwich panels of various types fabricated of aluminum and graphite/epoxy composite facings bonded to aluminum and phenolic fiberglass (HRD) cores were subjected to 30-day accelerated aging exposures to high humidity (95% RH) and salt spray environments. Sandwiches were tested for flatwise tensile and flexural strength before and after environmental aging. In addition, weight loss determinations and visual examination of corrosion effects were performed. Severe galvanic corrosion was found on graphite/epoxy-aluminum core sandwiches during and after the salt spray exposure, and mechanical strength retention was drastically reduced. Those sandwiches made of graphite/epoxy-aluminum core incorporating a 5-mil-thick glass fabric interliner in the core-to-face bonds (between the facings and the modified epoxy adhesive) withstood salt spray exposure extremely well, i.e., no evidence of galvanic corrosion or significant reduction of mechanical strength properties occurred. None of the sandwich types tested were affected by the 30-day 95% relative humidity exposure at 120 degrees F. (Author)