BAA-11-04-PKV-SOO3.doc

Low Cost Light Weight High Speed Structures – Independent Analysis Program

AFRL/RB is currently funding the Low Cost Light Weight High Speed Structures (LCLWHSS) program to develop designs for and test large integrated hot composite structures for hypersonic vehicles. The objective of this program is to provide an independent analysis of those designs.

Low Cost Light Weight High Speed Structures Program – Prime Contractor Activities

The following is being performed by the LCLWHSS contractor:

The LCLWHSS program will develop global vehicle and local detailed sub element, component, and fuselage designs and finite element models for a Mach 6 hypersonic vehicle. The proposed vehicle structural design incorporates ceramic and polymer matrix composites into a unitized hybrid hot structure. The design is intended to provide an integrated thermal protection system capable of carrying a portion of the vehicle mechanical loads. A global vehicle model will be developed to provide structural and thermal sizing. Global model results will subsequently be used as a starting point for detailed analysis and sizing of designs for sub element, component and fuselage test articles. These models will most likely rely on: 1) solid elements assuming quasi-isotropic in-plane properties to represent composite structure; 2) simplifying assumptions; and 3) idealized loads and boundary conditions. Ultimately, test articles for a robust test program within the primary LCLWHSS contract will be fabricated based upon these designs.

The LCLWHSS test program is based upon a building block approach that progresses from coupons, through sub element, and component testing before conducting full-scale tests on a segment of the vehicle fuselage. Planned tests include thermal, mechanical and possibly acoustic testing at conditions representing real world loads ranging from taxi to hypersonic flight loads.

Low Cost Light Weight High Speed Structures – Independent Analysis Objectives and Tasks

This program has as its primary objectives: 1) to provide independent evaluation of the LCLWHSS program non-proprietary detailed sub element, component and fuselage designs and models, and their loads and boundary conditions. 2) As appropriate, to develop enhanced finite element models (i.e. including detailed lamina geometry) to verify results produced by quasi-isotropic finite element analysis results, or to provide high fidelity results with which to evaluate subsequent test results. These objectives are to be met by conducting pre and post-test analyses in coordination with the LCLWHSS program schedule such that pre-test analysis results can where necessary impact testing and post-test analysis results will support analysis of test results. 3) The contractor will work jointly with Government engineers to analyze non-proprietary designs and evaluate results to provide the Air Force with an enhanced level of understanding of the design and models. In some cases it may be necessary to incorporate detailed model results into the proprietary global finite element models to update loads. This analysis will be conducted and provided by the Government.

Task 1 – Detailed Sub element, Component and Fuselage Design Analysis

Currently, up to four sub element test articles including CMC, PMC and hybrid (CMC /PMC) Pi joints and a hybrid scarf type joint are planned along with up-to two large ( approximately 2’ x 2’) components. The final test article is a full scale fuselage segment approximately 30 inches in diameter and 60 inches long. Starting with finite element models for each, provided by the government:

a) Conduct independent analysis to evaluate non-proprietary contractor FEA models, designs, loads, boundary conditions and assumptions. Identify areas of concern and their possible impact on design performance.

b) Modify existing or develop new models incorporating enhanced fidelity in areas including mesh size and composite lamina representation, loads and boundary conditions, and assumptions.

c) Compare original and modified model results and identify significant differences which may impact structural performance or failure mode.

d) Make recommendations for preferred modeling approach.

Task 2 – Sub element, Component and Fuselage Pre-Test Analysis

a) Utilizing the best models from task 1, conduct pre-test analysis of each test article based upon test conditions.

b) Predict response, failure location and failure mechanism.

Task 3 – Sub element, Component and Fuselage Post-Test Analysis

a) Conduct post-test analysis of test results to validate or make informed changes to FEA models and assumptions.

b) Make recommendations for design changes to improve structural performance in support of full scale fuselage test article development based upon task 3a and task 2 results.