Mechanical and fracture properties of concrete reinforced with recycled and industrial steel fibers using Digital Image Correlation technique and X-ray micro computed tomography

The application of fiber-reinforced polymer (FRP) composites is continuously increasing due to their superior mechanical properties and the associated weight advantage. However, they are susceptible to more complex types of damage, and advanced damage characterization systems are required to prevent catastrophic failures. Various non-destructive testing and evaluation (NDT&E) and in-situ structural health monitoring (SHM) techniques have been applied for damage detection in FRP composites. These techniques have been continuously developed to achieve reliable inspections, especially for safety-critical applications such as the aerospace industry. This review presents recent advances in NDT&E techniques and SHM techniques, particularly for damage diagnosis in FRP composites. For selecting the most suitable NDT technique based on specific criteria, the analytical hierarchy process is applied as a decision-making tool to evaluate and rank the NDT techniques. The size of the specimen is found to be the most important criterion that significantly affects technique selection. Finally, the importance of developing in-situ SHM systems is outlined, and different in-situ SHM systems are then reviewed and discussed. This review provides progress of the recent damage characterization techniques and enables researchers to devise selection criteria to select the most appropriate technique for their own work.

Advancements in fiber-reinforced polymer composite materials damage detection methods: Towards achieving energy-efficient SHM systems

Using digital image correlation for characterizing the elastic and plastic parameters of ultrafine-grained Al 1050 strips fabricated via accumulative roll bonding process

The ability to accurately determine elastic properties of orthotropic materials is important in the design and health assessment of composite structures. Direct methods using strain gauges and extensometers for estimating orthotropic properties have become popular in recent years. In cases where strains are highly localized, the material properties are inhomogeneous, or the material has localized damage, the use of these measurement schemes often provides insufficient information. To address this, we propose an inverse method, based on quasi-static elasticity imaging (QSEI) for determining inhomogeneous orthotropic elastic properties using distributed displacement measurements obtained from digital image correlation (DIC). The QSEI-based approach is first tested with simulated noisy displacement data considering in-plane deformations of plate geometries undergoing stretching and bending. Following this, experimental DIC measurements are applied to test the feasibility of the QSEI-based approach. Elastic properties of uni-directional CFRP beams with and without localized damage are estimated using the proposed approach. Results demonstrate the feasibility of the proposed inverse approach.

/pdf/coupled-digital-image-correlation-and-quasi-static-ju26k2rhfy.pdf

Coupled digital image correlation and quasi-static elasticity imaging of inhomogeneous orthotropic composite structures

Meso-mechanical investigations on the overall elastic properties of multi-phase construction materials using finite element method

Characterization of elastic constants of anisotropic composites in compression using digital image correlation

The invention relates to a roll for manufacture of a fibrous web, which comprises cellulosic fibres. The roll comprises a cylindrical surface, and a roll cover, which covers the cylindrical surface, and which comprises at least one uniform cover layer which is obtained by applying a cover composition comprising a rubber phase, polyurethane elastomer precursors based on polyols and isocyanates, and a chain extender onto the cylindrical surface of the roll. The cover layer is subjected to vulcanization, wherein the formed cover layer comprises a continuous rubber matrix formed from rubber phase, and domains of polyurethane elastomer embedded within the continuous rubber matrix. The invention relates also to a method for making the roll.

Heikki Kettunen

Papers

Characterization of elastic constants of anisotropic composites in compression using digital image correlation

Roll for manufacture of a fibrous web and method for making it