Experimental determination of mechanical properties of a single-ply broken twill 1/3 weave reinforced shape memory polymer composite

Thin weave reinforced composites are promising aerospace materials because of their advantages of high deformability, stiffness and strength. However, their tensile, compressive, shear and flexural mechanical properties typically behave differently due to the heterogeneous layout of the reinforcements. In this paper, a recently developed single-ply broken twill 1/3 weave-reinforced polymer composite intended for shape memory applications was thoroughly investigated. The large textile unit cell and ultra-thin specimen made the conventional test fixtures unsuitable. Newly modified compressive and shear test fixtures were proposed to provide reliable measurements. Due to the yarn crimps, the tensile stress-strain curves exhibited obviously three-stage nonlinear characteristics, and the compressive constitutive curves displayed significant stiffness degradation. The resin-dominated shear property values were less than 1/10 of those in tension. Affected by the yarn thickness and layout, the ratios of flexural moduli to tensile moduli were approximately 0.6. In general, this study provides basic observations and comprehensive test guidelines for understanding the mechanical properties of single-ply woven composites.