Viscoelastic relaxation in bolted thermoplastic composite joints

dc.contributor.advisorHorn, Walter J.
dc.contributor.authorSchmitt, Ron R.
dc.date.accessioned2011-11-23T21:39:26Z
dc.date.available2011-11-23T21:39:26Z
dc.date.copyright2011en
dc.date.issued1991-12
dc.descriptionThesis (M.S.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering.en_US
dc.description.abstractResults from a research program to investigate the long term effects of through-the-thickness fastener clamp-up force (preload) relaxation on the strength of mechanically fastened joints for two graphite/thermoplastic composite materials (Dupont's IM6/KIII and ICI-Fiberite's IM8/APC(HTA)) are summarized and compared with analytical methods. An experimental program was conducted in which 56 mechanically fastened single-shear joints were tested. Phase I static tests established joint bearing strength as a function of clamp-up force for two types of fasteners (protruding head and countersink) with no relaxation of preload. Phase II testing monitored short-term fastener preload relaxation (up to 1 ,000 hours), with special bolt force sensor washers. Inservice parameters included were temperature, in-plane loads, and torque. The jOints were tested to failure at the end of the relaxation time period to determine any subsequent effect on joint strength. Phase I test results indicated that joint bearing strength increased by as much as twenty-eight percent over the clamp-up force range of a Ibs (fingertight) to 3,500 Ibs for both materials. Fastener head type, material, and temperature also affected the resultant bearing strength. For Phase II, fastener clamp-up force at room temperature (78°F) relaxed an average of six percent from the initial value during the short-term test period. The relaxation was projected to be as high as fourteen and sixteen percent at 100,000 hours for HTA and Kill, respectively. The elevated temperature condition (250°F) significantly increased the relaxation rate with the projected 100,000 hour relaxation amount being as high as thirty-seven percent for HTA and sixty percent for Kill. Comparison of the Phase II bearing strengths to the Phase I results indicated that portions of the data correlated well, while others did not. It was concluded that relaxation of the clamp-up force over the short-term time period did not significantly lower the bearing strength of either material, however an extended exposure to 250°F could affect the bearing strength.en_US
dc.format.extentxx, 217 p.en
dc.identifier.othert91001
dc.identifier.urihttp://hdl.handle.net/10057/3988
dc.language.isoen_USen_US
dc.publisherWichita State Universityen_US
dc.rightsCopyright Ron R. Schmitt, 1991. All rights reserveden
dc.subjectThermoplastic composite jointsen_US
dc.subjectComposite materialsen_US
dc.subject.lcshElectronic dissertationsen
dc.subject.lcshJoints (Engineering)-- Testing
dc.subject.lcshComposite materials
dc.titleViscoelastic relaxation in bolted thermoplastic composite jointsen_US
dc.typeThesis
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