Multifunctionality of Polymer Composites

Challenges and New Solutions

Klaus Friedrich, Ulf Breuer

• Publisher: William Andrew
• Year: 2015
• eBook ISBN: 9780323265034
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

Approx.964 pagesApprox.964 pages

Section III

Applications

Outline

Part I Transportation

Part II Tribology

Part III Electrical Components

Part I

Transportation

Outline

Chapter 11 Development of multifunctional composites for aerospace application

Chapter 12 Lightweight structural composites with electromagnetic applications

Chapter 13 Carbon and metal-fiber-reinforced airframe structures

Chapter 14 Multifunctional carbon nanotube-based nano-composites for aerospace applications

Chapter 15 Multifunctional hierarchical nanocomposite laminates for automotive/aerospace applications

Chapter 16 Synergistic effect of carbon nanotube and graphene on multifunctional properties of their polymer composites

Chapter 11

Development of multifunctional composites for aerospace application

Xiao-Su Yi, Beijing Institute of Aeronautical Materials (BIAM), Beijing, PR China

Carbon–fiber-reinforced polymer composite structures are widely used in today’s aerospace industries. However, the introduction of the composites in mainframes of modern structures presents special challenges and issues regarding their impact damage resistance due to the brittle nature of the matrix resins and the multifunctional properties (e.g., electrical conductivity) because the composite structures are poor conductors of extreme electrical currents generated by a lightning strike.

For the technological challenge, the first approach, the so-called ex situ toughening technology in the chapter, is associated with the use of amorphous thermoplastic films as interleaves. When an interleaved composite laminate with a thermosetting matrix is cured, highly toughened thin interlaminar regions are established with phase separation and phase inversion. The technology is further developed to meet the challenge of cost-effective liquid moulding by developing preform-based fabrics, the so-called ES™-Fabrics. Improved interlaminar fracture toughnesses, compression after impact (CAI) strength, and balanced in-plane mechanical properties have been achieved.

The second approach is the use of the interleaf material surface coated with conducting silver nanowires (AgNWs). Typical interleaf materials include the thermoplastic films perforated and plastic veils. The AgNWs are deposited on the interleaf surface and even across its thickness; they densely interconnected with each other to form a conductive network like a “spiderweb.” In this way, two interdependent network structures coexist at different scales. On the one hand, the film or veil framework at the micron scale is essential for interleaf toughening, with a substantial improvement in interlaminar fracture toughness, G_IC and G_IIC. On the other hand, it provides a mechanism for adding nanoscale AgNWs. By incorporating the interleaf materials into the laminated composite system, a nanoscale, 3D cross-linked AgNW network is established throughout the whole composite, providing a clear improvement in electrical conductivity in the transverse and thickness directions of the carbon–fiber composites. The technology is thus called functionalized interlayer technology (FIT). The key advantage of such a technique is that it can significantly and simultaneously increase the impact damage resistance and electrical conductivity of structural composites by selectively interleaving the functionalized interleaf materials.

Keywords

Impact damage resistance; compression after impact; ex situ toughening; liquid moulding; preform-based toughening; ES™-Fabrics; electrical conductivity; interlaminar fracture toughness; functionalized interlayer technology

11.1 Introduction, Motivation, and Technological Challenge

Laminated carbon–fiber-reinforced polymer matrix composites are increasingly used in many industries, particularly in aerospace—e.g., in the design of leading edges, wing skins, helicopters, propeller blades, and engine ducts. Composite materials also begin to feature in primary structures, such as complete wing and fuselage assemblies. A typical example is demonstrated in B 787 Dreamliner (Figure 11.1). However, the design and application of such components or structures in a manner that ensures their safe operation under severe external impact loadings and environmental conditions has been a challenging task. Unlike metallic components, which can yield and dissipate energy via plasticity, composites can only dissipate energy by different damage such as delamination or fracturing processes, which usually degrade the stiffness and strength of the structural component. Therefore, the ability to have high impact damage resistance and tolerance of the composites used in aircraft remains a critical issue in the aerospace industry [1–4].

Figure 11.1 B787 Dreamliner and its use of the structural composites. Boeing open web site.

Facing the material challenge in impact damage performance, a roadmap for research and development (R&D) of the aerospace composites was proposed by Airbus (Figure 11.2). In the map, the first generation of composites shows either higher compression strength or compression after impact (CAI) strength. Accompanying the course of advancement of reinforcing carbon fibers, the second generation of composites developed displays higher compression strength in average; however, the CAI property remains apparently unsatisfied. The third generation includes the typical thermoplastic matrix composite like polyetherether ketone (PEEK) and some of the highly toughened epoxy matrix composites, e.g., 3900 (T800H/3900-2 carbon/epoxy composite) in the figure, whose interface contains a discrete thin layer of toughened thermoplastics. However, the thermoplastic composites PEEK generally involve costly manufacturing processes, and the highly toughened epoxy-like 3900 is typically used in the intermediate temperature range. Obviously, aerospace industry looks continuously for composites that have higher compression strength and CAI simultaneously at sufficiently high hot–wet glass transition temperature. For this end, an integrated approach that takes all disciplines into account is necessary.

Figure 11.2 Roadmap of development for aerospace composites. Airbus (2006).

Current state-of-the-art aerospace composites in application are principally prepreg-based. Correspondingly, the autoclave process prevails in this industrial branch. However, a trade-off exists between the performance and affordability for aircraft structures manufactured using prepreg materials and autoclave. The paramount need for the aerospace composites industry can be simply stated as an ongoing search for high-performance materials that can be produced at a low cost. Figure 11.3 shows for example the European vision [5]. Clearly, a 40% cost saving and a 30% weight saving compared to the state-of-the-art cannot be reached by small steps. Improved manufacturing technologies are the primary key to better affordability and quality. It is envisaged that the manufacturing methods will in the near future transfer from autoclave to liquid-molding approaches such as resin transfer molding (RTM), vacuum-assisted RTM (VARTM), and resin film infusion (RFI). To have such processes supplant autoclave manufacturing methods, liquid-molded composites need to have mechanical properties that meet or even exceed those available from the prepregs. Because the fibers used in liquid molding are the same as used in prepregs, mechanical-property improvements must depend on improved matrix resins and preforms. This is obviously a challenging task, particularly for maintaining the equivalent impact damage properties that the state-of-the-art prepreg materials possess.

Figure 11.3 European goals for weight and cost reduction on future Airbus planes [5].

Having been toughened for higher impact damage properties, however, the aerospace structural composites are difficult to achieve simultaneous multiple functionalities. Among many function-integrations that ar...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Preface
• List of Contributors
• Section I: Introduction to Multifunctional Polymer Composites
• Section II: Use of Special Matrices/Reinforcements/Interphases
• Section III: Applications
• Section IV: Smart Materials and Future Trends
• Index