Structural Adhesives

6Inelastic Response of Structural Aerospace Adhesives

Yi Chen and Lloyd Smith*

Washington State University, Pullman, WA, USA

Abstract

Most bonding in the aerospace industry relies on structural adhesives with high strength to achieve good bond quality in load bearing structures. As polymers, the mechanical behavior of adhesives, especially inelastic deformations corresponding to the durability of the bonded system, are complicated and in need of study. Considering both experimental and theoretical work, this chapter reviews the inelastic response of structural aerospace adhesives from time-independent plastic behavior to time-dependent inelastic behavior focusing on creep and cyclic responses. The influences of temperature and moisture on inelastic behaviors are also discussed.

Keywords: Structural adhesive, plasticity, viscoelasticity, viscoplasticity, creep, ratcheting, temperature, moisture

List of Symbols

ε ,	Tensile strain and tensile strain rate
t	Time
D0	Instantaneous tensile compliance
∆D	Transient tensile compliance
σ	Tensile stress
Di	ith Prony compliance
λi	ith retardation time
E	Stiffness of an elastic spring
η	Viscosity
a1i, a2i, a3i, b1i, b2i	Constants in the modified Burger model
g0, g1, g2, aσ	Nonlinear viscoelastic parameters
ψt	Reduced time
eij	Deviatoric strain tensor
εkk, θ	Volumetric strain
Sij	Deviatoric stress tensor
J0, B0	Instantaneous shear and bulk compliances
∆J, ∆B	Transient shear ...