N092-098 TITLE: Novel Analytical Methods for Sandwich Core Termination Features

TECHNOLOGY AREAS: Air Platform, Materials/Processes

ACQUISITION PROGRAM: F-35

OBJECTIVE: Develop and demonstrate approaches to successfully analyze sandwich core termination regions.

DESCRIPTION: Sandwich structure often offers the most structurally efficient and lowest cost solution for airframe and propulsion (nacelle) structure. However in order for sandwich panels to interface with substructure and accommodate penetrations, the core must be ramped down to a solid laminate region. This core termination region offers many challenges to properly design and verify its structural integrity. In addition to the numerous failure modes that can be present as a result of both in plane and out of plane loads, these termination regions are sensitive to manufacturing variations such as inconsistent radii. These factors make designing and analyzing the core termination region costly and time consuming. Industry currently lacks methods to reliably predict each failure mode including the effects of manufacturing variations. The objective of this effort is to develop and demonstrate approaches that can provide the information necessary to support the design and analysis of sandwich termination regions. Novel analytical approaches that can be used at both the global level and, where necessary, the local level are desired.

PHASE I: Develop approach and determine the feasibility for both global and local level analysis of core termination regions.

PHASE II: Develop the detailed approach and demonstrate both the global and local level analytical methods. The analytical approaches must consider the possible manufacturing and geometric variations that are possible in the termination region.

PHASE III: Transition developed technology to interested platforms and commercial interests.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The approaches and processes developed should be readily applicable to commercial aerospace where both propulsion and airframe applications are seeking to utilize greater amounts of sandwich composite structure to lower cost and weight.

REFERENCES:
1. Composite Materials Handbook CMH-173F; http://www.lib.ucdavis.edu/dept/pse/resources/fulltext/HDBK17-3F.pdf

2. Alfano and Crisfield, " Finite element interface models for the delamination analysis of laminated composites -mechanical and computational issues," International Journal for Numerical Methods.in Engineering, Volume 50, Issue 7, pp 1701-1736, 2001.

KEYWORDS: Composite; Sandwich Structure; Core; Honeycomb Core; Structural test; Analysis

** TOPIC AUTHOR (TPOC) **

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