Longitudinal Mechano-Sorptive Creep Behavior of Chinese Fir in Tension during Moisture Adsorption Processes.

Hui Peng,Jiali Jiang,Jianxiong Lu,Jinzhen Cao

doi:10.3390/ma10080931

Abstract

To provide comprehensive data on creep behaviors at relative humidity (RH) isohume conditions and find the basic characteristics of mechano-sorptive (MS) creep (MSC), the tensile creep behaviors, “viscoelastic creep (VEC)” at equilibrium moisture content and MSC during adsorption process, were performed on Chinese fir in the longitudinal direction under 20%, 40%, 60% and 80% RH (25 °C) and at 1, 1.3, and 1.6 MPa, respectively. The free swelling behavior was also measured, where the climate conditions corresponded with MSC tests. Based on the databases of free swelling, VEC, and MSC, the existence of MS effect was examined, and the application of the rheological model under the assumption of partitioned strain was investigated. The results revealed that both VEC and MSC increased with magnitude of applied stress, and the increasing RH level. Under all RH isohume conditions, the total strain of MSC was greater than that of VEC. The influence of RH level on VEC was attributed to the water plasticization effect, whereas that on MSC was presumed to be the effect of water plasticization and unstable state in the wood cell wall. In addition, the RH level promoted the relaxation behavior in MSC, while it slightly affected the relaxation behavior in VEC. In the future, the rheological model could consider the link between load configuration and the anatomic structural feature of wood.

Highlights

Creep, the study of the time-dependent strain behavior of polymeric materials, is defined as continuous deformation with time when subjected to a sustained load
Wood, being a hygroscopic material, adsorbs or desorbs moisture with changes in environmental conditions such as relative humidity (RH) and temperature to attain equilibrium moisture content (EMC) [6,7,8,9]
EMC were used to measure free swelling deformation at 20%, 40%, 60% specimens and 80% RHwith make were sure specimens were straight tests, a pre-load force of used to measure free in swelling deformation at 0.01

Summary

Introduction

The study of the time-dependent strain behavior of polymeric materials, is defined as continuous deformation with time when subjected to a sustained load. The assessment of creep behavior (immediate and long-term strains) of polymeric materials is the primary consideration for the in-service design of polymeric materials used in load-bearing components, such as reinforced concrete floors of buildings [1,2,3]. As a sustainable building material, exhibits creep behavior because of its viscoelastic nature [4,5]. A particular characteristic of wooden load-bearing elements is that their creep behavior strongly depends on the moisture content (MC) conditions [10,11,12]

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