Strain Localisation in iPP/MWCNT Nanocomposites Using Digital Image Correlation

Abstract

Polypropylene/multiwall carbon nanotube nanocomposites with different rates of weight incorporation (0–1%) were prepared by melt compounding and cast extrusion. The effect of maleic anhydride (5 wt%) grafted on polypropylene is studied through mechanical tests at different scales and morphological observations. In particular, the micromechanism of deformation was investigated through instrumented tensile experiments (at a macro and micro scales) using of a non‐contact method known as digital image correlation. The objective of this paper is first to characterise global behaviour (Young modulus, tensile strength, and ultimate properties) and second to go further in local analysis. In particular, optical instrumentation enables estimation of strain profile distribution onto the sample in a constricted area. Statistical parameters extracted from these local profiles are promising tools to enhance mechanical properties in link with microstructural composition. Tensile tests confirm composite reinforcement at a low level of nanocomposite incorporation, and local analysis enables quantitative measurements of adding maleic anhydride in formulations. The results reveal that addition of maleic anhydride delays strain localisation in the necked area.

Fracture monitoring of steel and GFRP reinforced concrete beams using acoustic emission and digital image correlation techniques

“…The red zones, representing a strain (ε xx ) of 1% or higher, indicate the presence of cracks. 50,51 A close matching and coherence are observed between AE-XY plots and DIC longitudinal strain profiles in the form of micro-and macro-cracking leading to final failure as observed visually in the actual beams at various stages of loading initiation-to-final failure. As the load increases, the 2D-DIC longitudinal strain (ε xx ) profile shows diminishing light bluish color at the 1.2 m for SR in Figure 8(b),(c) and 0.88 m for GR Figure 9(b),(c) RC from the left support.…”

Experimental assessment of low velocity impact damage in flax fabrics reinforced biocomposites by coupled high-speed imaging and DIC analysis

“…The image post-processing is based on a three-step DIC approach developed inhouse called CinEMA. The definition of the parameters used for the DIC and the details of the algorithm is described in [26,27]. In the first step, the rigid body displacement is calculated by a 2D cross correlation of the selected subimages.…”

Grain-to-Grain Interaction Effect in Polycrystalline Plain Low-Carbon Steel within Elastic Deformation Region

“…The inherent Young’s modulus of the grain ( E 0 ) is equal to the Young’s modulus of a single crystal with the same crystal orientation. The Young’s modulus of the single crystal can be measured via several methods which are suitable to the bulk material: Hooke’s law [ 1 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ]: A simple tension (or simple compression) test is performed to obtain a stress–strain straight line within the elastic deformation region. The gradient of this line is the Young’s modulus.…”

“…For different scale lengths, different speckle patterns should be used [ 21 ]. DIC was used to measure the macrostrain of a bulk material, and the Young’s modulus of the bulk material was successfully determined from the obtained stress–strain curve [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. Recently, research was carried out to determine appropriate experimental conditions, such as subset size and speckle, for micro- and mesoscale DIC [ 20 , 21 , 22 , 23 , 24 ].…”