Field Strain Measurement on the Fiber Scale in Carbon Fiber Reinforced Polymers Using Global Finite-Element Based Digital Image Correlation

• Main Author: Tao, Ran
• Other Authors: Lubineau, Gilles
• Language: en
• Published: 2015
• Subjects: Image Correlation; electron microscopy; Distortion; Conformat Mesh; Composite
• Online Access: http://hdl.handle.net/10754/554399

Laminated composites are materials with complex architecture made of continuous fibers embedded within a polymeric resin. The properties of the raw materials can vary from one point to another due to different local processing conditions or complex geometrical features for example. A first step towards the identification of these spatially varying material parameters is to image with precision the displacement fields in this complex microstructure when subjected to mechanical loading. This thesis is aimed to accurately measure the displacement and strain fields at the fiber-matrix scale in a cross-ply composite. First, the theories of both local subset-based digital image correlation (DIC) and global finite-element based DIC are outlined. Second, in-situ secondary electron tensile images obtained by scanning electron microscopy (SEM) are post-processed by both DIC techniques. Finally, it is shown that when global DIC is applied with a conformal mesh, it can capture more accurately sharp local variations in the strain fields as it takes into account the underlying microstructure. In comparison to subset-based local DIC, finite-element based global DIC is better suited for capturing gradients across the fiber-matrix interfaces.