  In this study, we investigate experimentally and numerically the mode I
intra-laminar fracture and size effect of Discontinuous Fiber Composites (DFCs)
as a function of the structure thicknesses.
  By testing geometrically-scaled Single Edge Notch Tension (SENT) specimens a
notable structure size effect on the nominal strength of DFCs is identified. As
the specimen size increases, the nominal strength decreases. For small
specimens, we find a limited size effect with enhanced pseudo-ductility and a
strong divergence from Linear Elastic Fracture Mechanics (LEFM). For
sufficiently large specimen sizes, the scaling of the nominal strength follows
closely LEFM with a strong brittle failure. As the thickness increases, the
size effect decreases.
  We identify the fracture energy and the effective size of the fracture
process zone as a function of the thickness of the structure. To do so, we
integrate equivalent fracture mechanics and stochastic finite element modeling.
Experimentally, we collect the nominal strength of geometrically-scaled Single
Edge Notch Tension (SENT) specimens. The numerical stochastic model captures
the complex, inhomogeneous mesostructure of DFCs by explicitly generating the
platelets. From the integrated analysis, it is found that the fracture energy
depends significantly on the structure thickness. It is shown to increase
gradually up to 2 mm and saturates after 3 mm to a value of 57.77 N/mm, which
is 4.81 times larger than a typical aluminum alloy.
