Application of Self Assembled Monolayer Approach to Probe Fiber Matrix-Adhesion
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AA10.4.1/DD11.4.1
Application of Self Assembled Monolayer Approach to Probe Fiber Matrix-Adhesion E. Feresenbet1, D. Raghavan1, G. A. Holmes2 1 Howard University Chemistry Department Washington, D.C. 20059 2 Polymer Division National Institute of Standards & Technology 100 Bureau Drive Stop 8543 Gaithersburg, Maryland 20899-8543 ABSTRACT Adhesion at the fiber-matrix interface of composites is often related to a combination of factors such as mechanical interlocking, physico-chemical interactions, and chemical bonding of the fiber-matrix interphase region. We demonstrate the use of self-assembled monolayer (SAMs) approach for depositing silane coupling agent on glass fiber and studying the impact of the individual interactions on the adhesion process. Through some unique chemistry, functionalized and non-functionalized C11 chlorosilanes were deposited on to E-glass fiber and modified. The adhesion of diglycidyl ether of bisphenol-A (DGEBA) cured with metaphenylene diamine (m-PDA) to SAM layer on E-glass fibers was measured by performing single fiber fragmentation tests (SFFT). The extent of adhesion between the fiber and matrix was found to be dependent on carbon chain length of coupling agents, and the functional group at the end of the SAMs layer. Furthermore, the contributions to adhesion by physico-chemical interaction and covalent bonding has been individually assessed. INTRODUCTION One of the major technical challenges to a composite’s use in high performance applications is the reliable prediction of long-term performance (e.g., failure behavior, fatigue behavior, durability, and stiffness). When composites are manufactured, a small region (< 1 µm), known as the fiber-matrix interphase, forms between the fiber and the matrix [1]. This region exhibits properties similar to, but distinguishably different from the properties of the bulk matrix [2]. Since stress is transferred between the fiber and matrix at the fiber-matrix interphase, the efficiency of this stress-transfer process at the interphase is critical to a composite’s ultimate strength and durability. Therefore, the role of the interphase structure, fiber topography, and fiber-matrix chemical bonding on ultimate composite performance needs to be understood fundamentally. Traditionally, a mole fraction of 50 % ω-aminopropyl trimethoxysilane (APS) coupling agent is applied on glass fiber and this coupling agent promotes adhesion between the glass fiber and epoxy matrix. However, the orientation of bonding sites in coupling agents (i.e., amino group in ω-amino propyl trimethoxysilane on the glass fiber) has been called into question and its impact on covalent bonding to the host matrix (epoxy) has not been fully understood. In recent years, molecular systems with well defined structural patterns have received growing attention for studying interfaces. A variety of experimental techniques have emerged
AA10.4.2/DD11.4.2
which allow one to endow a solid surface with rich, well defined chemical patterns while keeping the surface flat on a molecular scale.
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