Long-term mechanical behavior of aramid fibers in seawater

Aramid fibers are today proposed in ropes and cables for marine applications. As these highly crystalline materials are loaded in tension for a longer period in seawater, their long-term mechanical behavior has to be understood. However, the response is time-dependent and exhibits a nonlinear effect with stress. In this study, two types of aramid fibers are studied: Twaron and Technora. Mechanical properties are measured using static tensile tests and creep-recovery tests. A nonlinear viscoelastic-viscoplastic model, based on the Schapery formulation, allows discriminating between the instantaneous and the time-dependent response as well as the reversible and nonreversible phenomena (plasticity). First, this procedure allows the overall mechanical behavior of the fibers to be compared, considering creep rate, plasticity, and instantaneous moduli. Then, using these parameters, the effect of the testing condition, air or seawater is studied. Finally, the effect of aging in seawater is quantified for both fibers.

[1]  Richard Schapery,et al.  Viscoelastic Characterization of a Nonlinear Fiber-Reinforced Plastic , 1971 .

[2]  Peter Davies,et al.  Degradation of aramid fibers under alkaline and neutral conditions: Relations between the chemical characteristics and mechanical properties , 2010 .

[3]  D. J. Johnson,et al.  Supramolecular structure of a high‐modulus polyaromatic fiber (Kevlar 49) , 1977 .

[4]  R. J. Morgan,et al.  The relationship between the physical structure and the microscopic deformation and failure processes of poly(p-phenylene terephthalamide) fibers , 1983 .

[5]  The stress and sonic modulus versus strain curve of polymer fibres with yield , 1999 .

[6]  Peter Davies,et al.  Degradation of Technora aramid fibres in alkaline and neutral environments , 2009 .

[7]  L. Allard,et al.  On the morphology of aromatic polyamide fibers (Kevlar, Kevlar-49, and PRD-49) , 1983 .

[8]  Richard Schapery.  Nonlinear Viscoelastic and Viscoplastic Constitutive Equations Based on Thermodynamics , 1997 .

[9]  J. Lai,et al.  An integral constitutive equation for nonlinear plasto‐viscoelastic behavior of high‐density polyethylene , 1995 .

[10]  Robert J. Young,et al.  Molecular deformation processes in aromatic high modulus polymer fibres , 1999 .

[11]  P. Perzyna.  Fundamental Problems in Viscoplasticity , 1966 .

[12]  M. Northolt.  Tensile deformation of poly(p-phenylene terephthalamide) fibres, an experimental and theoretical analysis , 1980 .

[13]  M. Northolt,et al.  Elastic extension of an oriented crystalline fibre , 1985 .

[14]  T. Gierke,et al.  Morphology of poly(p‐phenylene terephthalamide) fibers , 1983 .

[15]  H. Yang.  Aromatic High-Strength Fibers , 1989 .

[16]  A. Bunsell,et al.  The creep of kevlar‐29 fibers , 1985 .

[17]  The viscoelastic extension of polymer fibres: creep behaviour , 2001 .

[18]  D. Dillard,et al.  Temperature and stress effects in the creep of aramid fibers under transient moisture conditions and discussions on the mechanisms , 1992 .

[19]  M. Northolt,et al.  Yielding and hysteresis of polymer fibres , 1995 .

[20]  R. Ericksen.  Creep of aromatic polyamide fibres , 1985 .

[21]  H. Yang,et al.  Kevlar Aramid Fiber , 1993 .

[22]  Emmanuel Chailleux,et al.  Modelling the Non-Linear Viscoelastic and Viscoplastic Behaviour of Aramid Fibre Yarns , 2003 .