Multi-Terrain Impact Tests and Simulations of an Energy Absorbing Fuselage Section

Abstract

Comparisons of the impact performance of a 5 ft diameter crashworthy composite fuselage section were investigated for hard surface, soft soil, and water impacts. The fuselage concept, which was originally designed for impacts onto a hard surface only, consisted of a stiff upper cabin, load bearing floor, and an energy absorbing subfloor. Vertical drop tests were performed at 25 ft/s onto concrete, soft soil, and water. Comparisons of the peak acceleration values, pulse durations, and onset rates were evaluated for each test at specific locations on the fuselage. In addition to comparisons of the experimental results, dynamic finite element models were developed to simulate each impact condition. Once validated, these models can be used to evaluate the dynamic behavior of subfloor components for improved crash protection for hard surface, soft soil, and water impacts.

Simulating the Response of a Composite Honeycomb Energy Absorber, Part 1: Dynamic Crushing of Components and Multi-Terrain Impacts

“…The sand was represented by an additional 84,672 solid elements that were assigned Mat 5, *MAT_SOIL_AND_FOAM, material property. Information on the characterization of the sand used in this model can be found in Fasanella (2007Fasanella ( , 2008. Like the rigid impact model, the fuselage orientation for sand impact was assumed to be perfectly vertical.…”

“…In fact, helicopter accident data indicate that more than 80% of crashes occur onto multi-terrain surfaces such as water, soft soil, plowed or grassy fields, and shallow swamps, as opposed to smooth prepared surfaces (Baldwin, 2000). In addition, research studies have shown that helicopters, designed for crash resistance onto hard surfaces, do not perform well during multi-terrain impacts (Sareen, 2002;Fasanella, 2007;Witlin, 1997;Tho, 2004;Kohlgruber, 2004;and Pentecote, 2002). For hard and nonyielding impact surfaces, the vehicle's kinetic energy has to be managed by the airframe and internal and/or external energy absorbing devices to ensure load attenuation and adequate post-crash cabin volume.…”

“…In particular, tests were performed onto a rigid concrete surface, water, and soft soil (sand). The composite fuselage section was developed during a prior research program (Jackson, 2001) at NASA Langley Research Center and was used as a test bed to evaluate the responses of seats and dummies , to study quantitative correlation methods including experimental uncertainty (Lyle, 2002), and to examine the influence of multiterrain (Fasanella, 2007). The fuselage section is fabricated using composite sandwich construction and details of its design can be found in Jackson (2001).…”

Size and shape optimization of aluminum tubes with GFRP honeycomb reinforcements for crashworthy aircraft structures

“…In order to measure its crashworthiness, an aircraft is tested under different situations, including bird strike simulations [2], impact on wings [3], and water ditching and crash landing scenarios on solid grounds [4,5]. These last situations, modeled with a vertical drop test, are commonly employed by structural designers to ensure the desired craft's performance.…”

Deployable System for Crash—Load Attenuation

“…The specimens do not collapse after maximum loading is achieved and exhibit a complex unloading response. The composite fuselage section was developed during a three-year research program in the late 1990's and has since been used as a test bed to evaluate structural scaling effects, multi-terrain impacts, seat and occupant loadings, and model correlation studies [22][23][24][25][26][27][28][29][30][31]. A pre-test photograph of the test article is shown in Figure 21 …”