No abstract

High-throughput, high-accuracy determination of thermal deformation and coefficient of thermal expansion (CTE) of carbon fibre-epoxy composites using 2D-digital image correlation (2D-DIC) is described. With the aid of a specially designed ultra-stable and high fidelity imaging system, which integrates a high-quality bilateral telecentric lens with monochromatic blue light illumination, surface images of multiple samples heated by a heating furnace can be captured simultaneously. The images of these samples at different temperatures are processed by advanced DIC algorithm to extract the thermal strains and the CTE of isotropic Al alloy, anisotropic unidirectional, and bidirectional carbon fibre-epoxy composites. Pure thermal expansions of these samples obtained after removing the small rigid-body rotations clearly indicate the isotropic and anisotropic expansions of these samples. The well-agreed results with literature values demonstrate the effectiveness and practicality of the proposed method for high-throughput and high-accuracy CTE measurements. KEYWORDScarbon fibre-epoxy composite, coefficient of thermal expansion, digital image correlation, high throughput, thermal strain

A single-camera special stereo-DIC (SS-DIC) is proposed for accurate virtual fields method (VFM) identification. The single-camera SS-DIC allows accurate surface 3D deformation measurements using a single colour camera and a specially designed colour separation device. It not only effectively eliminates the unavoidable out-of-plane movement/rotation due to unideal in-plane loading but also delivers uniformly distributed measurement points that brings great simplicity and convenience for internal virtual work calculation in VFM. In addition, since only a single camera is used for stereovision, the proposed SS-DIC system requires no complicated synchronisation devices. The effectiveness and practicality of the proposed method are evaluated by heterogeneous deformation experiments of a holed aluminium alloy and 304 stainless steel plate. Combined with a high-speed colour camera, the proposed method is expected to be a simple and practical method for the calibration of material constitutive model under intermediate and high strain rate conditions using VFM. KEYWORDS full-fields measurement, stereo-digital image correlation, virtual fields method