Experimental investigation of trans-scale displacement responses of wrinkle defects in fiber reinforced composite laminates

TL;DR

This paper investigates the trans-scale displacement responses of wrinkle defects in fiber reinforced composites using modeling and experimental methods, highlighting measurement techniques for different displacement magnitudes.

Contribution

It introduces a meso-mechanical model for wrinkle response and compares Shearography and FPP measurement methods for various displacement scales.

Findings

Finite element simulation predicts out-of-plane displacement from nanoscale to millimeters.

Shearography and FPP measurement sensitivities are quantitatively compared.

The study provides a reference for non-destructive testing of wrinkle defects in composites.

Abstract

Wrinkle defects were found widely exist in the field of industrial products, i.e. wind turbine blades and filament-wound composite pressure vessels. The magnitude of wrinkle wavelength varies from several millimeters to over one hundred millimeters. Locating the wrinkle defects and measuring their responses are very important to the assessment of the structures that containing wrinkle defects. A meso-mechanical modeling is presented based on the homogenization method to obtain the effective stiffness of a graded wrinkle. The finite element simulation predicts the trans-scale response of out-of-plane displacement of wrinkled laminates, where the maximum displacement ranges from nanoscale to millimeter scale. Such trans-scale effect requires different measurement approaches to observe the displacement responses. Here we employed Shearography (Speckle Pattern Shearing Interferometry) and fringe projection profilometry (FPP) method respectively according to the different magnitude of displacement. In FPP method, a displacement extraction algorithm was presented to obtain the out-of-plane displacement. The measurement sensitivity and accuracy of Shearography and FPP are compared, which provides a quantitative reference for industrial non-destructive test.