Artificial Thermal Ageing of Polyester Reinforced and Polyvinyl Chloride Coated Technical Fabric

Summary

Here, we simulate accelerated thermal ageing of technical fabric and see how this ageing process influences the mechanical properties of the fabric.

Abstract

Architectural fabric AF9032 has been subjected to artificial thermal ageing to determine changes of the material parameters of the fabric. The proposed method is based on the accelerated ageing approach proposed by Arrhenius. 300 mm x 50 mm samples were cut in the warp and fill directions and placed in a thermal chamber at 80 °C for up to 12 weeks or at 90 °C for up to 6 weeks. Then after one week of conditioning at ambient temperature, the samples were uniaxially tensioned at a constant strain rate. Experimentally, the parameters were determined for the non-linear elastic (linear piecewise) and viscoplastic (Bodner–Partom) models. Changes in these parameters were studied with respect to the ageing temperature and ageing period. In both cases, the linear approximation function was successfully applied using the simplified methodology of Arrhenius. A correlation was obtained for the fill direction between experimental results and the results from the Arrhenius approach. For the warp direction, the extrapolation results exhibited some differences. Increasing and decreasing tendencies have been observed at both temperatures. The Arrhenius law was confirmed by the experimental results only for the fill direction. The proposed method makes it possible to predict real fabric behavior during long term exploitation, which is a critical issue in the design process.

Introduction

Polyester based architectural fabrics are commonly used for construction of hanging roofs¹. Being relatively cheap with good mechanical properties, they can be employed in long-term exploitation (e.g., the hanging roof of the Forest Opera in Sopot - Poland). Unfortunately, weather conditions, ultraviolet radiation, biological reasons, and operational purposes (season pre-stressing and loosening²) can affect their mechanical properties. Hanging roofs made of AF9032 are typically seasonal structures subjected to high temperature (especially during sunny days in the summer), regular pre-tensioning and loosening. In order to....

Protocol

1. Accelerated thermal ageing experiments on technical fabric

1. Overall preparation
   1. Prepare a testing machine with proper software (in order to provide constant strain rate tests) and a video extensometer.
   2. Prepare a thermal chamber providing constant temperature of 80 °C (± 1 °C) and 90 °C (±1 °C) for at least 12 weeks.
2. Specimen preparation
   1. Unroll the technical fabric AF9032 bale. Draw the desired shapes (300 mm x 50 mm) with a soft pencil or marker on the fabric surface parallel to the warp or fill direction.
      NOTE: The distribution of specimens on the fabric surface is given elsewhere

Results

Figure 2 juxtaposes the stress-strain curves for the warp and fill directions of AF9032 fabric obtained at different ageing times, in the 80 °C temperature level for a strain rate of 0.001 s^-1. The difference between the 1 h ageing period (reference test) and the rest of the ageing periods is clear. The ageing time does not seem to substantially affect the material response in the warp direction, as the stress–strain curves are highly repetitive, showing no important differences i.......

Discussion

This article incudes a detailed experimental protocol to simulate the laboratory accelerated experiments on polyester reinforced and PVC coated fabrics for civil engineering applications. The protocol describes the case of artificial thermal ageing only by the means of raising the ambient temperature. This is an obvious simplification of real weather conditions, as UV radiation and water influence play an additional role in material service ageing.

Generally, the conditions of accelerated agei.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
AF 9032 technical fabric	Shelter-Rite Seaman Corporation
knife of scisors
marker			pernament
ruler
Sigma Plot	Systat Software Inc.	v. 12.5
Testing machine Z020	Zwick Roell	BT1-FR020TN.A50
TestXpert II program	Zwick Roell	v. 3.50
Thermal chamber	Eurotherm Controls	2408
tubular spanner			13 mm
Video extensometer	Zwick Roell	BTC-EXVIDEO.PAC.3.2.EN	Instead of video extensometer, a mechanical one can be used
VideoXtens	Zwick Roell	5.28.0.0 SP2