A study on residual stresses in polymer composites using moiré interferometry

Abstract

Moiré interferometry is applied along with the hole drilling technique to determine residual cure stresses in symmetric cross ply graphite epoxy laminates. Traditional moiré interferometry set-up using two collimated angle beams was employed to provide the virtual reference grating while a cross grating with a frequency of 1200 lines per mm was replicated on the specimen surface. Holes of different depths, each one penetrating one additional layer of the laminate, were drilled using a high speed air turbine drill to relieve the stresses in each layer sequentially. The strain distribution around each hole was computed from correlation of the undistorted carrier fringe pattern with the distorted fringe patterns around the holes. The measured strain distributions are compared to residual strain distributions by finite element analysis.

Recent progress in residual stress measurement techniques

“…In 2004, Shankar and Xie et al [34] conducted a study on the residual stress within polymer composites, and Xie et al [35] studied the residual deformation in lap-welded steel plates, as shown in Fig.3. Chang et al [36] applied a phase-shift moiré interferometry method combined with the blind-holedrilling for composite materials.…”

Residual Stress Determination by Hole Drilling Combined with Optical Methods

“…Moire-hole drilling method has been applied to quantify residual stresses from various manufacturing processes such as grinding [32], laser welding [33] and shot peening [34]. It has also been applied in recent years to determine residual stresses in fiber reinforced composites [35][36][37][38], apparently more so than any other hole drillingoptical technique to date.…”

The Influence of Coating Fabrication Processes on the Optical Efficiency of Replicated Moiré Diffraction Gratings

“…In the last decades, the optical experimental technique, Moiré Interferometry, has been implemented in many fields, of which the most important are the material characterization [2][3][4], microelectronics devices [5,6], micromechanics [7,8], fracture mechanics [9][10][11], the residual stress [12][13][14], composite materials [15,16] and biomechanics [17,18]. For all these cases the main goal is the global measurement of displacement fields without contact with high resolution and accuracy that the Moiré Interferometry method can offer.…”