Repair of Polymer Composites

Methodology, Techniques, and Challenges

Andrew J. Jefferson, V. Arumugam, Hom Nath Dhakal, Hom Dhakal

• Publisher: Woodhead Publishing
• Year: 2018
• Print ISBN: 9780081019085
• eBook ISBN: 9780081019092
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

Repair of Polymer Composites: Methodology, Techniques, and Challenges discusses fundamental issues related to the repair of composites and their suitability in various industrial sectors, such as aerospace, automotive, marine and construction, etc. The repair of composites is complex and requires a thorough understanding of the various types of damage mechanisms in order to apply the appropriate NDT techniques. This book explores these issues in significant detail and presents systematic procedures and methods, thus serving as a useful reference for both undergraduate and postgraduate students, academic researchers, engineers and other professionals who are interested in this exciting field of research. - Discusses fundamental issues related to the repair of composites and their suitability in various industrial sectors, including aerospace, automotive, marine and construction, etc. - Provides comprehensive coverage, from the fundamental aspects, to real applications - Serves as a useful reference for both undergraduate and postgraduate students, academic researchers, engineers and other professionals - Presents different types of repair techniques by correlating different parameters and challenges

1

Introduction and context

Abstract

Advanced polymer matrix composite materials have obtained popularity in high-performance structural applications such as automobile, marine, and aerospace structures. This chapter provides a brief introduction to composite materials and repair. Initially, the types, advantages, limitations, applications, and role of different constituents of composites are discussed. Different categories of reinforcements (e.g., tows, mats, and braids) and matrix (e.g., thermoset matrix composites and thermoplastic matrix) systems are discussed. This is essential to make known to the readers who are new to the topic with the terms and technology of fiber-reinforced polymer matrix composite materials. Subsequently, the properties of composite materials are briefly explained. Its addition is required for completeness so that the reader could understand the intricacy of the topic. Finally, the need for repair in composite structures is discussed. This section familiarizes the readers with the importance of repair and the industrial necessities involved in repairing composites.

Keywords

Composite materials; Fibers; Matrix/resin materials; Interface; Failure behavior; Properties of composites; Repair of composites

Acknowledgment

The authors would like to thank Dr. Gracy Paulin D and Mrs. Jensolin Ebenezer for their generous suggestions and support that greatly contributed in improving the final version of the chapter.

1.1 Introduction

A heterogeneous composite material is a mixture of two or more different materials to take the benefit of the good features of each of them. The constituents are mixed at the macroscopic scale and are not soluble to each other. Advanced composite materials fabricated employing matrices and reinforcements of different forms have been applied as alternate materials to conventional metals in marine, automobile, and aerospace sectors. The development of boron- and carbon-fiber reinforcements (in the 1960s) made the turning point in the composite material revolution [1]. These reinforcements, which have superior mechanical properties than glass-fiber reinforcements, gave a considerable rise in the mechanical properties of composite structures. Advanced composites have been employed to prepare numerous structural components in engineering applications owing to their several attractive characteristics such as high strength-to-weight and stiffness-to-weight ratio, superior fatigue resistance, and excellent corrosion resistance. Their better mechanical properties and ability to tailor their constituents to the exact requirements are the motivation behind this broad application. In addition, the capability to fabricate components with complicated geometry employing smaller amount of parts allows fabricators to save cost as compared with the similar components of metallic materials. The high specific strength and stiffness properties of carbon fiber-reinforced polymer matrix composites (PMCs) made them more appropriate for aircraft, automobile, and sports application. The better resistance of glass fiber-reinforced PMCs to environmental attack made them more suitable for marine applications.

Initial evaluation and development of the fiber-reinforced PMCs originated in the defense sector, where composite materials were used to fabricate rocket-motor cases [2]. Investigation of this material began primarily in the defense sector to reduce the high costs associated with fabrication of these structures. As fabrication methodologies improved, costs associated with processing and fabrication of composite laminates reduced to a point where these materials could be economically applied in various primary and secondary load-carrying structures. Nowadays, aircraft constructors utilize laminated composites to fabricate a wide range of external structural components such as rudder, flaps, elevators, and spoilers [3]. The Boeing 787 Dreamliner and Airbus A350-XWB are the new commercial aircrafts that show a considerable increase in the application of composite materials. Competition between aircraft manufacturers has accelerated the use of fiber-reinforced composites in fan blades of the turbine engine, upper fuselage, leading edges of stabilizers, doors, interiors, and primary wing structure as in the Airbus A380 or Boeing 787 Dreamliner. As compared with the Boeing 777 introduced in year 1994, the new Boeing 787 demonstrates an enhancement from around 12% composite materials to around 50% by weight, respectively, reflecting on reducing weight, owing to considerably higher fuel price and also a higher confidence in designing and fabricating with this material.

1.2 Classification and definitions

Composites consist of blends of two or more different ingredients separated by a different interface. The ingredient that is continuous and usually measuring in a larger amount is called the matrix system. It is the matrix characteristics that are enhanced on adding another ingredient to make a composite [4,5]. The most important intention of the matrix system is to surround and unite the fiber, hence efficiently distributing load to it and shield it from exterior and unreceptive surroundings. The bulk of composites presently applied implies polymeric matrices, but ceramic matrix is also implied in high-wear, high-temperature applications. The second ingredient in a composite material is the fiber system, which is fabricated using a stiffer and stronger material than the matrix system. The fibers are the main load-bearing component in the composite material, and its configuration, shape, and volume critically influence the properties of the composite. As per the matrix system, composites are grouped into polymer matrix, ceramic matrix, or metal matrix composites (MMCs). Moreover, in accordance with the fiber configuration, it can be grouped into particulate fiber reinforced, chopped strands reinforced, and continuou...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• About the authors
• Preface
• Acknowledgments
• 1: Introduction and context
• 2: Overview of different damage and common repair methods in composite laminates
• 3: Key stages of adhesively bonded repairs
• 4: Design, analysis, and durability of composite repairs
• 5: Safety and precautions
• Index