The Analysis of Stress Raisers Affecting the GFRP Strength at Quasi-Static and Cyclic Loads by the Theory of Critical Distances, Digital Image Correlation, and Acoustic Emission

Abstract

The purpose of this work is to analyze the stress-raisers that affect the tensile strength and fatigue resistance of GFRP parts using the point and line methods of the theory of critical distances (TCD) to obtain a quantitative measure of the defect size that can be tolerated by the composite before it fails. In the course of the work, a method combining TCD and the Weibull function was developed. In the course of the work, GFRP structural fiberglass for electrical purposes was tested under uniaxial quasi-static and cyclic loading with digital image correlation (DIC) and acoustic emission (AE), as well as a numerical simulation of deformation. The studied specimens were plain (without a stress-raiser) and notched (V-shaped) with different notch root radii and depths. The results were used to determine the material critical distances. In this case, two approaches to TCD were used: line (LM) and point (PM) methods. To analyze the experimental results, finite element modeling was applied using the ANSYS software package. As a result, the linearized maximum principal stresses were obtained on the central line passing through the top of the stress raiser. Thus, the values of the critical distances of the material were determined by PM and LM. Based on the data obtained, the sizes of permissible defects in the studied fiberglass were established that do not affect the tensile and fatigue strength of the material. The paper illustrates the cumulative energy, peak amplitudes, and distributions of the frequency of the spectral maximum of acoustic emission signals obtained after the destruction of specimens by fatigue test. Evolutions of deformation fields on the specimen surface were recorded using a Vic-3D contactless optical video system and the DIC.

Tension and Shear Behaviour of Basalt Fiber Bio-Composites with Digital Image Correlation and Acoustic Emission Monitoring

“…Acoustic emission testing has proven to be a suitable non-destructive method for the damage characterisation of FRP composites and other engineering materials. It can be used as a standalone technique or in combination with other NDT methods [28][29][30][31][32][33][34][35][36][37][38]. In the literature, some characteristic parameters of acoustic emission (AE) signals are used to describe crack modes and damage mechanisms [28,39,40].…”

Mechanical behavior of fiber-glass plastic with hole pattern using digital image correlation and acoustic emission methods

“…An important scientific direction includes experiments with the use of combined methods to study the fracture of composite objects with concentrators in the form of holes. In the studies of many authors [31][32][33] the prospect of joint use of video system of non-contact measurement and analysis of displacement and deformation fields for the analysis of mechanical behavior of composites, calculation methods, infrared thermal scanning systems and acoustic emission method is noted. The joint use of these methods is conditioned by the necessity of obtaining additional important information on determining the moment of damage initiation and its location, on defect propagation in the material.…”

A Coupled Tensor–DEM–FEM Model for the Whole Process of Internal Fine-Scale Damage to Surface Damage in Red-Bed Soft Rocks in the Coastal Area of South China

“…This is what makes the correlation characterization of internal and external damage and its calculation based on acoustic emission and DIC techniques in red-bed soft rock a key to research. Especially the characterization and calculation of the whole process of internal microscopic damage to surface damage are hot spots [15,16]. At present, the characterization and calculation of the whole process of internal microscopic damage to surface damage in red-bed soft rock are mainly based on other rock methods.…”