Greenstick fracture in composite pultruded rods

The paper analyses the greenstick fracture mode on anisotropic beams subjected to flexural loading. This fracture mode can be seen in plant branches, young mammal bones or reinforced plastic rods. Two analytical models have been studied: a straight beam model and a uniform curved beam model. Circumferential normal stress distribution has been determined considering the classical beam theory, and radial and shear stresses have been predicted by using the Airy's stress function. Experimental work has been implemented on initially straight pultruded rods with longitudinally oriented fibres. Three and four-point bending tests adopting several span-to-diameter ratios have been performed. Experimental conditions that promote a greenstick fracture mode in composite pultruded rods have been considered.