Project Abstract

Abstract
The research project focuses on investigating the fracture response and cumulative damage of e-glass fiber reinforced composite materials under tensile and flexural stresses. E-glass fiber composites are widely used in various engineering applications due to their superior strength and stiffness properties. Understanding the fracture behavior and damage accumulation in these composites is essential for ensuring the structural integrity and reliability of components made from these materials. The research methodology involves conducting tensile and flexural tests on e-glass fiber reinforced composite specimens to evaluate their mechanical properties and fracture behavior. Tensile tests are performed to study the material's response to uniaxial loading, while flexural tests are conducted to analyze the material's behavior under bending conditions. The tests are carried out under different loading conditions to simulate real-world scenarios and to investigate the material's mechanical performance under various stress states. In addition to mechanical testing, advanced analytical techniques such as digital image correlation (DIC) and acoustic emission (AE) monitoring are employed to study the damage evolution and fracture mechanisms in the composite materials. DIC provides high-resolution full-field deformation measurements, allowing for the visualization and analysis of strain distribution and damage accumulation during loading. AE monitoring detects and locates the initiation and propagation of cracks in the material, providing valuable insights into the fracture process. The research aims to characterize the fracture response of e-glass fiber reinforced composites by analyzing the stress-strain behavior, failure mechanisms, and damage accumulation under different loading conditions. By correlating the mechanical test results with the observations from DIC and AE monitoring, a comprehensive understanding of the material's fracture behavior is achieved. This knowledge can be used to optimize the design and performance of components made from e-glass fiber composites, leading to enhanced structural integrity and durability. Overall, the research project contributes to the advancement of knowledge in the field of composite materials by investigating the fracture response and cumulative damage of e-glass fiber reinforced composites. The findings from this study can have implications for various engineering applications where these materials are utilized, such as aerospace, automotive, and construction industries.

Project Overview

INTRODUCTION

Insufficient knowledge of composite durability and the lack of life prediction methodologies for predicting glass fiber-reinforced composite material durability and damage tolerance are the mitigating factors against the readily acceptance of fiber-reinforced plastics (FRP) in the marine and civil infrastructure. In order to increase the use of composite materials in the infrastructure arena, the nature and effect of the service environment on the durability of glass fiber-reinforced composite materials must be investigated and appropriate methods established for assessing service life. The knowledge of the mechanics and kinetics of glass-polymer system degradation is essential for the formulation of analytical tools for the characterization of fiber- reinforced composites. The absence of a unified theory for the complete characterization of glass fiber-reinforced composites systems is the major challenge facing the composite industry. In addition to lack of predictive tools, the composite industry is also confronted with little data. The data currently available is industry-specific. Most of the data belong to the aerospace and petrochemical industries where years of exposure to composites have resulted in a databank while little data is currently available for the marine and infrastructure sectors. The absence of glass fiber-reinforced data for marine and infrastructure application where longevity is the objective function has been responsible for the slow acceptance of the use composites in the marine and infrastructure arena. This growing interest in the application of composite materials in the infrastructure sector has begun a more rigorous approach in the evaluation of these materials to ensure that they perform within expected hygro-thermal-mechanical environment. The absence of significant data characterizing the long-term durability of glass fiber-reinforced polymeric composites and the absence of adequate established standards for the repair, design, and maintenance of glass fiber-reinforced composite have been the mitigating factors against the introduction of composites to industry. In order to circumvent the restrictions imposed by the absence of long-term data, simulation and other stochastic methods have been envisioned. These simulations provide insights into the long-term response of glass fiber-reinforced composite materials or their constituents to combined environments. The lack of long-term data is not only restricted to the physical response of composite materials in the application environment but also the environmental and chemical synergism responsible for the premature failure of glass fiber-reinforced composite materials. Another salient advantage of a reliable simulation technique is that it allows for the establishment of performance bounds for the material. Performance bounds are essential because even though we may know the mechanics of environ-mechanical degradation and can describe it, we still have no predictive way of assessing the mechanical and environmental loading (severity and sequence) that the application environment will impose. Thus, the path-dependent damage process that the composite experiences will never fully allow one precise assessment of the remaining strength and life.

The failure of glass fibre reinforced composites under single and repeat impact (fatigue) has been of concern to the designer and users of aerospace structures. because their specific properties make them attractive for mobile applications which often experience cyclic loading of the component materials of fibre reinforced plastics, the dominant reinforcement, E-glass, is known to suffer from a loss of strength with time under load due to a stress- corrosion mechanism common in inorganic glasses. Thus, clear understanding of the fatigue behaviour is essential in the proper use of the composite materials.

The concept of “fatigue” was introduced by wohler to classify material degradation or failure which was proportional to the number of cycles of applied load. Recently, the term has been associated with self-similar single crack growth in homogeneous materials, and crack growth rates have become the single most common design approach for dealing with such behavior. The fatigue behavior of the composite materials cannot be described in that way since the complexity of the internal microstructure of those materials introduces a wide range of fatigue damage modes that normally act in concert with one another to produce a collective result.

Specifically, quantitative information on damage evolution and accumulation, and accompanying property degradation is necessary in the analysis, design and life prediction to insure structural integrity and reliability.

1.1 Relevance of Research

The research has shown us that beyond a certain crack length of (2.00mm), many small cracks form in the matrix and in the reinforcement the material is expected to fail catastrophically without warning.

More so, the fatigue damage of composites has described the failure mode of composites as a “collective failure mode” not as “single failure mode”.

1.2 Objectives of Research

The research objectives are as follows:

To study the homogenous behaviour of fatigue damage in a selected E-glass fibre composite subject to cyclic tensile loading.
Study the basic nature of damage development, fundamental to the understanding of cyclic degradation and failure behaviour.
To determine the effects of these micro-cracks experimentally through
(i) The change in material stiffness

(ii) An empirical fatigue damage growth law in existence

4) An experimental program is conducted first to provide information on micro-crack initiation, growth and associated characteristics for subsequent analysis.