Combined Tension-Torsion Loading of Braided Composite Structures

Braided composites are a class of composite materials. They feature an inter-woven structure that improves structural stability and damage tolerance. Presently, braided composites under tension and torsion loading have been studied individually. Mechanical behaviour of braided composites under combined tension-torsion loading is common, yet no studies have explored this effect. In this study, mechanical properties of carbon fibre, fibreglass and Aramid 2D tubular braided composites (TBCs) were assessed and compared under coupled tension-torsion loading. Failure mechanism of braids was investigated by the plane stress theory. A contact-free three-dimensional digital image correlation (3D DIC) technique was used to derive detailed and continuous strain maps and understand buckling behaviour of TBCs. Benefitting from this research experiment, combined loading as a common and critical loading condition can be analyzed more realistically and accurately in designing elements out of braided composites to prevent structural failures.