202. DAMAGE OF HIGH ENERGY WIDE AREA BLUNT IMPACT TO COMPOSITE AIRCRAFT FUSELAGE STRUCTURE
Name: Moonhee Nam
Grad Year: 2018
As the largest impact damage source to commercial composite aircraft structures, High Energy Wide Area Blunt Impact (HEWABI), caused by accidental contact with ground service equipment (GSE), leaves low externally visible damage but induces significant internal damage. In the past years, the research has been conducted in UCSD funded by Federal Aviation Administration (FAA) to address this problem by identifying damage mechanism in composite aircraft fuselage structures and developing Finite Element (FE) modeling capability to predict structural response, damage progression and formation caused by GSE impact. Current on-going research, as extended topics of the HEWABI project, is focused on: (i) characterization of key damage modes developed in composite frame via element-level experiments, (ii) establishment of FE modeling methodology validated by the small-scale experiments, (iii) definition of a large quarter-barrel GSE impact test specimen including passenger and cargo floor joints and their stiffness interactions. Element-level C-frame bending and combined bending-torsion tests were conducted to excite relevant failure modes that were observed in past large specimen blunt impact tests. The specimens were composed of a short section of C-frame inserted into an extension arm and tested as a combined fixed-end cantilever beam. Compression flange postbuckling first developed prior to abrupt failure adjacent to the fixed-support. FE model development is being developed using 8-node continuum shell elements. Key challenges to overcome are the accounting for slipping of the specimen from the fixtures. Additionally, a quarter-barrel large test specimen design is in progress to address questions on how the frame interactions with the floor structure affect damage formation during blunt impact loading. This entails benchmarking existing composite-dominated large commercial aircraft fuselage designs to identify typical structure configuration, size, manufacturing processes and other characteristics. Preliminary design of new shear tie, stringer and floor structures to reflect these commercial aircraft configurations is under way.
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