A composite skid landing gear design investigation has been conducted. Limit
Drop Test as per Federal Aviation Regulations (FAR) Part 27.725 and Crash test
as per MIL STD 1290A (AV) were simulated using ABAQUS to evaluate performance of
multiple composite fiber-matrix systems. Load factor developed during multiple
landing scenarios and energy dissipated during crash were computed. Strength and
stiffness based constraints were imposed. Tsai-Wu and LaRC04 physics based
failure criteria were used for limit loads. Hashin s damage initiation criteria
with Davila-Camanho s energy based damage evolution law were used for crash.
Initial results indicate that an all single-composite skid landing gear may
not be feasible due to strength concerns in the cross member bends.
Hybridization of multiple composites with elasto-plastic aluminum 7075 showed
proof of strength under limit loads. Laminate tailoring for load factor
optimization under limit loads was done by parameterization of a single variable
fiber orientation angle for multiple laminate families. Tsai-Wu failure
criterion was used to impose strength constraints. A quasi-isotropic N = 4
(pi/4) 48 ply IM7/8552 laminate was shown to be the optimal solution with a load
factor under level landing condition equaling 4.17g s. LaRC04 predicts that
failures will be initiated as matrix cracking under compression and fiber
kinking under in-plane shear and longitudinal compression.
All failures under limit loads being reported in the metal-composite hybrid
joint, the joint was simulated by adhesive bonding and filament winding,
separately. Simply adhesive bonding the metal and composite regions does not
meet strength requirements. Filament wound bolted metal-composite joint shows
proof of strength. Filament wound composite bolted to metal cross member radii
is the final joining methodology.
Finally, crash analysis was conducted as per requirements from MIL STD 1290A
(AV). Crash at 42 ft/sec with 1 design gross weight (DGW) lift was simulated
using ABAQUS. Plastic and friction energy dissipation in the reference aluminum
skid landing gear were compared with plastic, friction and damage energy
dissipation in the hybrid metal-composite design. Damage in composites was
modeled as progressive damage with Hashin s damage initiation criteria and
Davila-Camanho s energy based damage evolution law. The latter meets
requirements of aircraft kinetic energy dissipation up to 20 ft/sec (67.6 kJ) as
per MIL STD 1290A (AV). Weight saving possibility of up to 49% over conventional
metal skid landing gear is reported.
The final design recommended includes Ke49/PEEK skids, 48 ply IM7/8552 cross
member tapered beams and, Al 7075 cross member bend radii bolted to the filament
wound composite tapered beam. Concerns in composite skid landing gear designs,
testing requirements and future opportunities are addressed.
| Identifer | oai:union.ndltd.org:GATECH/oai:smartech.gatech.edu:1853/24763 |
| Date | 27 June 2008 |
| Creators | Shrotri, Kshitij |
| Publisher | Georgia Institute of Technology |
| Source Sets | Georgia Tech Electronic Thesis and Dissertation Archive |
| Detected Language | English |
| Type | Dissertation |
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