Characterisation of material properties for draping of dry woven composite material

Three test methods, uniaxial bias extension, biaxial and picture frame tests are used to characterise the shear behaviour of dry woven fabric during draping. The deformation of the bias extension and biaxial specimens is measured from images of a central gauge section. The forces applied to the material are resolved into forces along and parallel to the tow directions. The deformation of the material in the bias extension and biaxial tests is found to behave in a manner which is reasonably well described by a pin-jointed net analysis. There is negligible change in the shear resistance of the material during biaxial loading, while a slight increase in shear resistance is observed in the picture frame tests. Microscopic examination of the tow architecture [Compos Sci Technol 63 (2003) 99], which shows a significantly smaller crimp amplitude for picture frame tests than for the bias extension and biaxial tests, supports the suggestion raised by Harrison et al. [Proceedings of the 10th European Conference on Composite Materials, 2002], that the increase in resistance in the picture frame tests is associated with an increase in tow cross-over force generated by large loads along the tows. q 2003 Elsevier Ltd. All rights reserved.