Design of free-form fabric structures

 




Tensioned fabric is being studied as a medium for sculpturing architectural enclosures in context of, (i) current and future climate change and the consequent demand for more out-door living spaces, and, (ii) the need for safe and efficient enclosures in areas prone to earthquakes or adverse weather conditions.

The lightweight nature and flexibility of fabric structures makes them versatile in application.  They can be used as mobile temporary solutions, or as semi-permanent enclosures.  However, fabric structures can be commercially unattractive.  This is largely due to the complexity of their design and a lack of understanding of the principles of optimum structural form; all too easily resulting in poor aesthetics, and durability. The latter can be attributed to inadequate form-finding and patterning.

In patterning, the central problem is that of accurate mapping and the judicious choice of the seam lines in the 3D surface. It has been proved that a string following a geodesic line (’shortest path’) on a curved surface has constant tension.  Consequently, a seam line following such a path reduces the opportunity for local wrinkling.  Much current design, however, uses rather crude approximations to seam lines/geodesics, resulting from faceted surface representations.

Under the proposed methodology, bi-cubic splines will be used to describe the 3D surface. This mathematical construct will ensure smooth representation of stress, deformation, and geometry.  Also, calculated and displayed surface curvatures will provide an informed choice for the location and direction of optimal (geodesic) seam lines. The display of stresses arising from mapping will indicate the likelihood of wrinkling, and this constitutes a novel step in the approach.

The patterning module will include the construction of a mathematical model for predicting physical properties of fabrics. Here, the development of a robust stress-strain relationship will utilise the results of bi-axial testing, (conducted by The Courtauld Institute of Art), for a variety of loading regimes and varying environmental conditions, such as temperature and humidity.  The accuracy of the model will be tested using full field two dimensional Electronic Speckle Pattern Interferometer (ESPI) measurements of the stress/strain fields in fabric panels. 

By focusing on minimum energy forms and appropriate patterning methodology, this project will demonstrate the design potential of fabric enclosures and assist in answering the demand for them as portable, easy to construct lightweight structures to suit contemporary environments.

Principal Investigator:
Dr Wanda Lewis
University of Warwick
T: 02476 523 138
E: w.j.Lewis@warwick.ac.uk