Spacecraft structures rely on honeycomb panels to provide a light weight means to support the vehicle. Honeycomb panels can carry significant load but are most vulnerable to structural failure at their joints where panels connect. This research shows that predicting sandwich panel joint capability using finite element analysis (FEA) is possible. This allows for the potential elimination of coupon testing early in a spacecraft design program to determine joint capability. Linear finite element analysis (FEA) in NX Nastran was used to show that adhesive failure can be predicted with reasonable accuracy by including a fillet model on the edge of the fitting. Predicting the ultimate failure of a joint using linear FEA requires that engineering judgment be used to determine whether failure of certain bonds in a fitting will lead to ultimate joint failure or if other bonds will continue to carry the joint's load.
The linear FEA model is also able to predict when the initiation of core failure will begin. This has the limitation that the joint will still be able to continue to carry significantly more load prior to joint ultimate failure even after the core has begun to buckle. A nonlinear analysis is performed using modified Riks' method in Abaqus FEA to show that this failure mode is predictable. The modified Riks' analysis showed that nonlinear post-buckling analysis of a honeycomb coupon can predict ultimate core failure with good accuracy. This solution requires a very high quality mesh in order to continue to run after buckling has begun and requires imperfections based on linear buckling mode shapes and thickness tolerance on the honeycomb core to be applied. / Master of Science / Spacecraft structures rely on honeycomb panels to provide a light weight means to support the vehicle. Honeycomb panels consist of two thin metal sheets separated by a light weight honeycomb grid. The panels operate in a similar way to how an I-Beam works on a bridge. These panels can carry significant load but are susceptible to failure because the panels must be glued together when they are built.
This research shows that predicting honeycomb panel joint capability using finite element analysis (FEA) is possible. FEA allows the engineer to model and predict failure in complex structures by mathematically combining many small shapes called elements which have known behaviors and properties into the shape of the actual tested article. The elements deflect in a known manner based on the load applied to the model. The honeycomb panel joint is predicted to break when the deflection in a particular element is higher than the element’s material capability. Obtaining the load where the panel breaks is critical information to have during the design of a spacecraft structure.
Using the techniques presented in this thesis allows for the potential elimination of coupon testing early in a spacecraft design program to determine joint capability. Coupon testing is where honeycomb panels are built and tested to failure. This testing is very expensive in terms of both cost and program schedule and therefore using analysis to eliminate its need or to reduce its scope provides significant benefit to the spacecraft program.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/77029 |
| Date | 04 April 2017 |
| Creators | Lyford, Andrew Lindquist |
| Contributors | Aerospace and Ocean Engineering, Kapania, Rakesh K., Patil, Mayuresh J., Seidel, Gary D. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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