Experimental study of the stress transfer in discontinuous composites on the basis of a unit cell model

In this study, composites with discontinuous 'brick-and-mortar' architecture, consisting of conceptually stiff load-carrying bricks connected by a mortar material, were treated. The bricks were composed of unidirectional pre-impregnated tapes with a thermoplastic matrix, and a very thin interface of thermoplastic material represented the mortar. The problem was simplified to a unit cell containing a single overlap between two bricks, where the stresses between the bricks are transferred purely by shear in the mortar material. The stress-strain response of the unit cell in tension was determined by experiments and compared to predictions by a numerical model available from literature, which is based on shear-lag stress transfer. The results showed that it is possible to create a highly non-linear stress-strain response with this ordered discontinuous architecture. The effect of the interface shear strength and fracture toughness and the influence of the brick geometry on the achievable tensile strength were discussed.