In this paper, the fracture behavior of two short fiber reinforced polymers is discussed. The two investigated materials are a polyphthalamide (PPA) with glass fiber inclusions of 33% (GF33) and a polyphenylene sulfide (PPS) with glass fiber inclusions of 40% (GF40). Due to the highly anisotropic behavior of these types of materials, most of the mechanical properties, including fracture toughness, are dependent on the fiber orientation. One parameter that directly affects the fiber orientation is the wall thickness. Single edge crack (SEC) test specimens were used to determine the cracking force under mode I (opening mode) loading conditions. The specimens were milled from plates at different orientations. Three fiber orientations were considered: 0°, 45° and 90°. Two different thicknesses of the plates were used: 2.0 mm and 3.2 mm.