Research Summary
Modeling of Water Slamming for Foam Core Sandwich Composite Structures
Authors: Y. Tsuchida (PhDCE), and J.W. Gillespie, Jr.
INTRODUCTION
Advanced composite sandwich structure is widely used as the primary hull structure of high-speed marine crafts.
Water slamming loads on the hull structure are crucial concern from the design perspective.
Design methods for the impulsive loads have not been established well.
Response of the composite sandwich hull structures needs to be predicted.
FE MODELING FOR WATER SLAMMING OF RIGID STRUCTURE
LS-DYNA (mpp971d R5.1.1) with double precision
Symmetric problem geometry
2-D analysis assuming a plane strain state
Non-reflecting boundaries on Exterior surfaces of the fluid domain
8 node solid elements for all parts : Multi-material ALE formulation for fluids, one point integration for structure.
Coupling force is computed and distributed on the structure (Lagrangian) element surface.
PREDICTION OF SLAMMING PRESSURE
Rigid hull structure of sandwich materials with density and elastic properties
Constant impact velocity corresponding to Sea State 6
No gravity effect
FEA results for slamming pressure are compared to the analytical solution by Wagner theory.
Fig 2: Slamming Pressure Distribution at Specified Time
PREDICTION OF SLAMMING PRESSURE
Explicit analysis to validate material model behavior in explicit time integration
2-D analysis assuming in-plane strain state for half symmetric model
Foam core material (CORECELL P600) model
The material behavior is defined by stress – strain relationship.
Negligible Poisson’s effect is assumed.
COMPARISON OF BEAM DEFORMATIONS
Contour of Vertical Displacement
FEA Result (The model is reflected about the symmetric plane)
DIC (Digital Image Correlation) Measurement
COMPARISON OF LOAD CURVES
The TPB simulation reasonably predicts the experimental behavior.
However, the simulation results show the stiffer behavior than the experiment. The possible reasons are:
Inertia effects,
Assuming the in-plane strain state,
Not modeling the interlayer between the facesheet and the core.
SUMMARY
The 2-D water slamming problem is modeled by the explicit FEA.
The fine mesh models show good agreement with the analytical solution on prediction of the slamming pressures for the rigid structure.
The deformable sandwich structure model reasonably predicts the experimental behavior in the explicit method.
Ongoing work is to predict the foam core response due to water slamming.
ACKNOWLEDGEMENTS
This work is supported by the Office of Naval Research through the Advanced Materials Intelligent Processing Center.
