A novel particle-filled carbon-fibre reinforced polymer model composite tailored for the application of digital volume correlation and computed tomography

Abstract

This paper presents the development of novel Carbon-Fibre Reinforced Polymer (CFRP) laminates, tailored for the application of Digital Volume Correlation (DVC) and Computed Tomography (CT) to experimental mechanics analyses of these materials. Analogous to surface-based Digital Image Correlation (DIC), DVC is a relatively novel volumetric method that utilizes CT data to quantify internal three-dimensional (3D) displacements and implicit strain fields. The highly anisotropic and somewhat regular/self-similar microstructures found in well-aligned unidirectional (UD) materials at high fibre volume fractions are intrinsically challenging for DVC, especially along the fibre direction at microstructural length-scales on the order of a few fibre diameters. To permit the application of DVC to displacement and/or strain measurements parallel to the fibre orientation, the matrix was doped with a sparse population of sub-micrometre particles to act as displacement trackers ( i.e. fiducial markers). Barium titanate particles (400 nm, ∼1.44 vol. %) were found to offer the most favourable compromise between contrast in CT images and the ability to obtain a homogeneous distribution in 3D space with sufficient particle compactness for local DVC analyses. This property combination was selected following an extensive Micro-focus Computed Tomography (µCT)-based qualitative assessment on a wide test matrix, that included 38 materials manufactured with a range of possible particle compositions, mean sizes and concentrations. By comparing the tensile behaviour of the particle-adapted material alongside its particle-free counterpart, we demonstrate through the application of in situ Synchrotron Radiation Computed Tomography (SRCT) that the macro- and micromechanical responses of the newly developed CFRP are consistent with standard production materials indicating its suitability as a model system for mechanistic investigations.

Fibre-direction strain measurement in a composite ply under quasi-static tensile loading using Digital Volume Correlation and in situ Synchrotron Radiation Computed Tomography

“…Previous studies have shown that for low particle concentrations, the mechanical properties of thermosetting matrices can be largely preserved [47], [48]. In turn, by comparing the micromechanical behaviour of the particle-adapted material alongside its particle-free counterpart, we demonstrate elsewhere [49] that the response of the newly developed CFRP is consistent with standard production materials suggesting its suitability as a model system for mechanistic investigations.…”

Detailed experimental validation and benchmarking of six models for longitudinal tensile failure of unidirectional composites

“…• Schöberl et al [49] found similar fibre break development for two nominally identical specimens, but one did not reach final failure. There were only 4 and 6 volumes available at different load steps.…”

“…Raman spectroscopy is necessarily restricted to imaging fibres at specimen surfaces, and, in most cases, to single fibre specimens or specimens with low volume fractions. In recent years, the focus of experimental validations has, therefore, shifted towards the use of synchrotron radiation computed tomography (SRCT) [16,[42][43][44][45][46][47][48][49][50]. SRCT allows three-dimensional in-situ observation of fibres within the bulk of composites, albeit with small imaging volumes (~1 mm 3 ) at the required resolution.…”

“…SRCT allows three-dimensional in-situ observation of fibres within the bulk of composites, albeit with small imaging volumes (~1 mm 3 ) at the required resolution. While methods to measure strain profiles are being developed [49,[51][52][53], the research has primarily focused on monitoring the development of fibre breaks and clusters thereof. Direct comparisons with model predictions have led to useful insights [16,32,42,43,54], but the models still need improvements in order to predict the coplanarity of the clusters [16] and size of the clusters [16,32,42,54].…”

Ultrasonication optimisation and microstructural characterisation for 3D nanoparticle dispersion in thermoplastic and thermosetting polymers

“…As a general trend, the particle size, or actually the aggregate or agglomerate cluster size, is stated to decrease with increasing energy density and shows an inverse power law behaviour (~𝐶. 𝐸 " 12 ) [31,36]. Nevertheless, large powers or times have resulted in possible re-agglomeration; hence, the optimisation and general trends of a developed ultrasonication procedure remain a system-specific challenge [18][19]22,38].…”