Fabrication and Testing of Durable Redundant and Fluted-Core Joints for Composite Sandwich Structures

The development of durable bonded joint technology for assembling composite structures is an essential component of future space technologies. While NASA is working toward providing an entirely new capability for human space exploration beyond low Earth orbit, the objective of this project is to des...

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Bibliographic Details
Published inNASA Center for AeroSpace Information (CASI). Conference Proceedings
Main Authors Lin, Shih-Yung, Splinter, Scott C, Tarkenton, Chris, Paddock, David A, Smeltzer, Stanley S, Ghose, Sayata, Guzman, Juan C, Stukus, Donald J, McCarville, Douglas A
Format Conference Proceeding
LanguageEnglish
Published Hampton NASA/Langley Research Center 06.05.2013
Subjects
Aircraft industry
Bonded joints
Composite structures
Compression tests
Compressive strength
Damage assessment
Damage detection
Design
Failure modes
Fuel consumption
Impact damage
Impact resistance
Low earth orbits
Moon
Polytetrafluoroethylene
Propagation modes
Sandwich structures
Space exploration
Stress concentration
Tensile tests
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Summary:The development of durable bonded joint technology for assembling composite structures is an essential component of future space technologies. While NASA is working toward providing an entirely new capability for human space exploration beyond low Earth orbit, the objective of this project is to design, fabricate, analyze, and test a NASA patented durable redundant joint (DRJ) and a NASA/Boeing co-designed fluted-core joint (FCJ). The potential applications include a wide range of sandwich structures for NASA's future launch vehicles. Three types of joints were studied -- splice joint (SJ, as baseline), DRJ, and FCJ. Tests included tension, after-impact tension, and compression. Teflon strips were used at the joint area to increase failure strength by shifting stress concentration to a less sensitive area. Test results were compared to those of pristine coupons fabricated utilizing the same methods. Tensile test results indicated that the DRJ design was stiffer, stronger, and more impact resistant than other designs. The drawbacks of the DRJ design were extra mass and complex fabrication processes. The FCJ was lighter than the DRJ but less impact resistant. With barely visible but detectable impact damages, all three joints showed no sign of tensile strength reduction. No compression test was conducted on any impact-damaged sample due to limited scope and resource. Failure modes and damage propagation were also studied to support progressive damage modeling of the SJ and the DRJ.