Structural Testing and Analysis of Honeycomb Sandwich Composite Fuselage Panels

摘要

This study investigated the damage tolerance characteristics and failure mechanisms of six honeycomb sandwich composite fuselage panels subjected to quasi-static pressurization and axial loading using the Full-Scale Aircraft Structural Test Evaluation and Research (FASTER) fixture located at Federal Aviation Administration William J. Hughes Technical Center, Atlantic City International Airport, NJ. The FASTER fixture is capable of testing full-scale fuselage panel specimens under conditions representative of those seen by an aircraft in actual operation. The faster fixture is capable of applying pressurization, axial, hoop, and shear loads to a fuselage panel. The damage tolerance of composite sandwich panels with impact damage, holes, and notches under in-plane tensile and compressive loading was previously investigated at coupon and element-scale levels. A typical airframe predominantly experiences in-plane loads, although damaged regions may experience localized out-of-plane bending and bulging due to internal pressurization. The objective of these tests was to study the effects of holes and notches on the damage tolerance of full-scale, curved composite panels that reflect a typical sandwich fuselage structure subjected to combined loading. All six panels were loaded quasi-statically up to failure, studying damage growth and strain redistribution behavior with increasing load and recording the residual strength. The test articles were instrumented with strain gages near the damage and in the far-field regions for strain surveys. A digital image correlation method was used to obtain full-field displacement and strain measurements at equal load intervals and after any visible surface damage was observed. The acoustic emission method was used to monitor for damage growth in real time and served as an early warning for imminent failure. Several nondestructive inspection methods, including flash thermography and computer-aided tap testing, were used to scan for nonvisual damage.