Sandwich Composites

Fabrication and Characterization

Senthilkumar Krishnasamy, Chandrasekar Muthukumar, Senthil Muthu Kumar Thiagamani, Sanjay Mavinkere Rangappa, Suchart Siengchin

• Publisher: CRC Press
• Year: 2022
• ISBN:
  9781000531701
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Mechanics

A composite sandwich panel is a hybrid material made up of constituents such as a face sheet, a core, and adhesive film for bonding the face sheet and core together. Advances in materials have provided designers with several choices for developing sandwich structures with advanced functionalities. The selection of a material in the sandwich construction is based on the cost, availability, strength requirements, ease of manufacturing, machinability, and post-manufacturing process requirements. Sandwich Composites: Fabrication and Characterization provides insights into composite sandwich panels based on the material aspects, mechanical properties, defect characterization, and secondary processes after the fabrication, such as drilling and repair.

FEATURES

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• Outlines existing fabrication methods and various materials aspects

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• Examines composite sandwich panels made of different face sheets and core materials

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• Covers the response of composite sandwich panels to static and dynamic loads

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• Describes parameters governing the drilling process and repair procedures

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• Discusses the applications of composite sandwich panels in various fields

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• Explores the role of 3D printing in the fabrication of composite sandwich panels

Due to the wide scope of the topics covered, this book is suitable for researchers and scholars in the research and development of composite sandwich panels. This book can also be used as a reference by professionals and engineers interested in understanding the factors governing the material properties, material response, and the failure behavior under various mechanical loads.

1 Introduction to Sandwich Composite Panels and Their Fabrication Methods

Athul Joseph

Indian Institute of Science

Vinyas Mahesh

Indian Institute of Science Nitte Meenakshi Institute of Technology National Institute of Technology Silchar

Vishwas Mahesh

Siddaganga Institute of Technology Indian Institute of Science

Dineshkumar Harursampath

Indian Institute of Science

DOI: 10.1201/9781003143031-1

Contents

1. 1.1 What Are Sandwich Composite Structures?
2. 1.2 Brief History of Sandwich Composite Structures
3. 1.3 Common Materials Used in Composite Sandwich Structures and Their Properties
   1. 1.3.1 Face Materials
   2. 1.3.2 Core Materials
      1. 1.3.2.1 Foams or Solid Cores
      2. 1.3.2.2 Corrugated or Truss Cores
      3. 1.3.2.3 Honeycomb Structures
   3. 1.3.3 Adhesive Materials
      1. 1.3.3.1 Epoxy Resins and Toughened Epoxies
      2. 1.3.3.2 Phenolics
      3. 1.3.3.3 Polyurethanes
      4. 1.3.3.4 Urethane Acrylates
      5. 1.3.3.5 Polyester and Vinyl Ester Resins
4. 1.4 Fabrication Methods for Composite Sandwich Laminates
   1. 1.4.1 Hand Layup Process
   2. 1.4.2 Compression Moulding Process
   3. 1.4.3 Filament Winding Process
   4. 1.4.4 Vacuum Bagging and Autoclave Moulding Process
   5. 1.4.5 Pultrusion Process
   6. 1.4.6 Resin Transfer Moulding (RTM)
   7. 1.4.7 Additive Manufacturing Processes
5. 1.5 Conclusions
6. References

1.1 What Are Sandwich Composite Structures?

Sandwich composite structures are a special class of laminated composites in which different forms of materials are bonded to each other to obtain a desired functionality. The overall behaviour of these composite structure is dependent on the properties of the constituent layers [1]. Conventionally, a sandwich composite structure consists of two main parts: the face sheets or faces and the core structure. Usually, the face sheets are adhesively bonded to the core on either side. Also, the face sheets are much thinner than the core as seen in Figure 1.1. The adhesive used to bond these two entities must have enough strength to withstand the stresses set up between the face and the core [2]. The basic principle of design for a sandwich composite structure is inspired from an I-beam (shown in Figure 1.2). In view of sandwich composite structures, the face sheets of the structure resemble the flanges of the I-beam and the core represents the web of the I-beam that connects both the flanges. The face sheets form a stress couple to counteract the bending stresses applied on the structure with one face under compression and the other under tension as seen in Figure 1.3 [3]. The core resists the shear loads and improves the stiffness of structure, providing adequate support to the face sheets. A continuous support is provided by the core structure so that a uniformly stiffened structure is obtained. Some of the primary advantages of sandwich composites are their very high stiffness-to-weight ratio and high bending strength-to-weight ratio coupled with good thermal insulation properties. Furthermore, some sandwich composite structures have excellent mechanical energy absorption characteristics, fatigue life and acoustical insulation. These characteristics of sandwich structures make them desirable in a lot of applications such as marine structures, aerospace components, automotive parts and civil engineering structures.

FIGURE 1.1 Depiction of a typical sandwich composite panel.

FIGURE 1.2 Structure of an I-beam.

FIGURE 1.3 Behaviour of sandwich composite laminates under bending forces.

1.2 Brief History of Sandwich Composite Structures

Sandwich constructions date back to 1849 when Noor, Burton and Bert stated the first use of sandwich construction back to Fairbairn in England in 1849 [4]. From there, a major development was seen when the Wright-Patterson Air Force Base designed and fabricated the Vultee BT-15 fuselage using fibreglass-reinforced polyester as the face material and both a glass-fabric honeycomb and a balsa core in 1943. However, the first documented research paper concerning sandwich construction was written by Marguerre [5] in Germany in 1944 to determine the in-plane compressive properties of sandwich panels. Hoff [6]put forth a set of differential equations and boundary conditions to analyse the bending and buckling of sandwich plates. The equations were derived using the principle of virtual displacements, which was primarily suited for buckling problem only. Shortly, a small deflection theory for sandwich plates was put forth by Libove and Batdorf [7]. Later in the year 1949, a structural optimization theory for sandwich panels was put forth by Flügge [8]. The study presented nomograms for the solution of several problems related to composites structures.

In 1956, Gerard [9]discussed different sandwich plate optimization routes in his book Minimum Weight Analysis of Compression Structures. Shortly, Kaechele [10] expounded on the minimum weight design of sandwich panels in a report submitted to the United States Forest Products Laboratory (USFPL). In 1966, Plantema [11], in the Netherlands, published the first book on sandwich structures, followed by another book by Allen in England in 1969. These books remained as the standard reference for composite structures until the mid-1990s. The first work on the finite element analysis of sandwich constructions was presented by Ha [12] in 1990. Since then, composite structures have evolved to be included in a wide variety of applications from aerospace structures to marine structures to automotive parts and many others, where effective weight reduction with uncompromised strength and stiffness was desired [13].

1.3 Common Materials Used in Composite Sandwich Structures and Their Properties

1.3.1 Face Materials

As discussed previously, the primary purpose of the face sheet is to resist the bending stresses applied on the sandwich laminate structure. In addition to this, properties such as high tensile and compressive strength, good impact resistance, good surface finish, environmental resistance and wear resistance are desirable to obtain strong and reliable structures [2]. The materials used for the face sheets are usually in the form of thin sheets. It is common to use both metals and non-metallic materials as face sheets, although the latter are widely preferred due to their excellent weight reduction and stiffness enhancement. Metallic materials vastly include steel, stainless steel and aluminium alloys. There are other alloys with better strength properties. However, they find limited applications due to their higher material density and limited stiffness variation. Non-metallic materials are the most common materials used for face sheets. Materials such as plywood, cement, plastics and fibre-reinforced plastics are the major ones used as face sheets in most of the applications. Engineering plastics such as polypropylene, polyamide and high-performance polymers such as polyetherimide (PEI) and polyether ether ketone (PEEK) have widely been used. In addition to this, the use of fibre-reinforced plastics has been effective in significantly reducing weight while providing sufficient mechanical capabilities for the structure. Some high-performance polymers such as PEI are used in sophisticated applications such as aerospace components.

1.3.2 Core Materials

Core materials should primarily possess low density in order to reduce the total weight of the sandwich structure as much as possible. Core materials are primarily subjected to shear stresses which produce global deformation as a result of the strains produced within the core m...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Preface
• Editors
• Contributors
• Chapter 1 Introduction to Sandwich Composite Panels and Their Fabrication Methods
• Chapter 2 Corrugated Core- and Fold Core-Based Sandwich Panels
• Chapter 3 Metallic Core- and Truss Core-Based Composite Sandwich Panels
• Chapter 4 Composite Sandwich Panels with the Metallic Facesheets
• Chapter 5 Failure Behavior and Residual Strength of the Composite Sandwich Panels Subjected to Compression after Impact Testing
• Chapter 6 Low-Velocity Impact Response of the Composite Sandwich Panels
• Chapter 7 High-Velocity Impact Properties of the Composite Sandwich Panels
• Chapter 8 Investigation of Blast Loading Response of the Composite Sandwich Panels
• Chapter 9 Flexural Behavior of Reinforced Concrete Sandwich Wall Panels Enabled by Fiber-Reinforced Polymer (FRP) Connectors
• Chapter 10 Axial Behavior of Reinforced Concrete Sandwich Wall Panels Enabled by Fiber-Reinforced Polymer (FRP) Connectors
• Chapter 11 Enhanced Failure Behavior for Sandwiches with Hybrid Wire Mesh/FRP Face Sheets
• Chapter 12 Low-Velocity Impact Behaviour of Textile-Reinforced Composite Sandwich Panels
• Chapter 13 Drilling and Repair of the Composite Sandwich Panels
• Chapter 14 Composite Sandwich Structures in the Marine Applications
• Chapter 15 Composite Sandwich Structures in Aerospace Applications
• Chapter 16 Crashworthiness Applications of the Composite Sandwich Structures
• Chapter 17 Role of 3D Printing in the Fabrication of Composite Sandwich Structures
• Index