Design of Sandwich Composites with Multi-Functional Facesheets
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Design of Sandwich Composites with Multi-Functional Facesheets 1
Uday K. Vaidya, 1Selvum Pillay, 1Helena Ricks, 1Shane Bartus, 2Chad Ulven and 2Biju Mathew Department of Materials Science & Engineering, 1 The University of Alabama at Birmingham, Birmingham, AL 35294, U.S.A. 2 Department of Mechanical Engineering, North Dakota State University, Fargo, ND 58105, U.S.A. ABSTRACT Sandwich composites find increasing use as flexural load bearing lightweight sub-elements in air / space vehicles, rail / ground transportation, marine and sporting goods. The core materials in these applications is usually balsa, foam or honeycombs, while laminated carbon or glass are used as facesheets. A limitation of traditional sandwich configurations is that the space in the core becomes inaccessible once the facesheets are bonded in place. Significant multi-functional benefits can be obtained by making either the facesheets or the core, space accessible. Multifunctionality is generally referred to as value added to the structure that enhances functions beyond traditional load bearing. Such functions may include sound / vibration damping, ability to route wires or embed sensors. The present work considers traditional core materials of nomex and aluminum honeycombs that possess functional space accessible facesheets, and their low velocity impact (LVI) response. INTRODUCTION Typically, a sandwich construction increases the bending stiffness of a structure without substantially increasing its weight [1-2]. Multi-functionality represents additional functions that can be incorporated within existing structure/component, that add value beyond conventional load bearing. The commercial applications (aerospace, marine and rail/ground transportation) of sandwich structures primarily utilize foam, balsa and honeycombs as core materials [1-2]. The limitation with the traditional core sandwich structures is the space inaccessibility to the core once the facesheets are bonded in place. Recent studies [3-6] have demonstrated the utility of reinforced cores that enables space access and enhanced damage tolerance within the core to increase functionality. Concepts studied include - three-dimensional (3D) Z-pins embedded into foam [3], foam-filled honeycomb core [4], integrated core and hollow / space accessible core [5]. The functions these designs can integrally accommodate include vibration damping, acoustical transmission/ absorption, noise control, ability to route electrical wires, store fuel, provide fire retardant capability, and ability to embed electronics/sensors etc. These benefits would be in addition to conventional load bearing, lightweight and high flexural strength / stiffness requirements. Space accessible facesheets
Sandwich Plate A 3D reinforced glass fabric consisting of two bi-directional woven fabrics, which are connected with vertical fibers are utilized as facesheets, as shown in Fig. 1. The two biU7.4.1
Honeycomb Core
Figure 1. Sandwich plate with space accessible facesheets
directional woven E-glass fabric surfaces are mec
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