Type of Document Master's Thesis Author Yalamanchili, Seshu R URN etd-11242009-020154 Title Response of multiple fastener composite joints :numerical and experimental results Degree Master of Science Department Engineering Mechanics Advisory Committee
Advisor Name Title Griffin, O. H., Jr. Committee Co-Chair Hyer, M. W. Committee Co-Chair Morris, Don H. Committee Member Keywords
Date of Defense 1992-05-05 Availability restricted AbstractThe response of flat multiple fastener composite joints with two rows of holes and four different widths was studied. The joint geometry was very specific, and three different laminates were also considered. The laminates were loaded in a double lap fashion with steel laps. Pins were used as fasteners. All the specimens were instrumented with strain gages at critical locations, namely, around the holes. Special pins were used to measure the load reacted by each pin in the joint. This information was used to determine the percentage of the total load reacted by each pin. Most of the specimens were tested to failure, though some specimens were stopped short of failure and examined for damage initiation through Xrays. A finite-element procedure for determining the load proportioning in the multiple-fastener joints was used to complement the experiments. The commercial finite-element program ABAQUS was used to predict the load proportioning among the pins using two independent plane stress finite-element models, one representing the composite specimen, the other representing the steel laps. The models interacted through rigid circular surfaces
representing the steel pins. Excellent correlation was obtained between experiments and
analysis for the percentage load proportioning. For the strains, the correlation between experiments and predictions was found to be excellent around the net-section region. Although
predictions for other strains were not as good, they were within the range of experimental
data. Distribution of contact stresses between the pins and the hole edges was also studied. Numerical analysis suggests that the prevalent assumption of radial cosine distribution
of contact stress between the pin and hole edge is in substantial error. It can also be
concluded that the strength of the joint is for the most part, independent of its width, though
for narrower specimens, the holes were quite highly loaded.
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