Study of a thick composite and aluminum single-lap bolt joint employing orthotropic photoelasticity and digital speckle pattern interferometry.

摘要

This thesis is part of a larger effort to research the strength of a single-lap, single-bolt joint between a thick Polymer Matrix Composite (PMC) and aluminum section that is representative of those to be employed on ARMY heavy-duty land vehicles. There has been little published research on the single lap bolted joint, which owes to the difficulty of such an analysis. The goal of this thesis was to contribute to the development of two experimental methods to analyze the stress distribution near the region around the bolt hole; then acquire results from those techniques to complement and verify the FEM stress predictions. The first method was an embedded polariscope orthotropic photoelastic stress analysis to study the contact stress distribution in the bearing plane of the composite between the bolt and bolthole. In order to model composite orthotropic behavior, a transparent birefringent orthotropic material was developed and characterized. The second experimental method was a Digital Speckle Pattern Interferometry (DSPI) surface strain analysis of the single-lap, bolted joint between composite and aluminum. Overall, the DSPI and photoelasticity results demonstrate that increasing bolt torque significantly decreases stress concentrations. Both methods need to be developed further in order to provide more information.