Mechanical and morphological properties of coextruded wood plastic composites with glass fiber‐filled shell

Coextrusion technology makes various properties of wood plastic composites (WPCs) highly tunable. However, structural and material optimization of core‐shell shaped WPCs is needed to balance manufacturing cost, processing efficiency, and product performance. In this study, various systems of coextruded WPCs were designed and analyzed using short glass fiber (SGF)‐filled shells in combination with three core systems (i.e., weak, moderate, and strong). A comparison of the composite flexural property of the manufactured WPCs (i.e., modulus and strength) shows that SGF reinforcements in the shell layer were optimized at high SGF loading levels regardless of core qualities. Also, SGF alignments in the shell layer played an important role in determining the flexural property of the WPCs. When the shell modulus and strength were lower than these of the core, the increase of shell thickness led to reduced composite properties. On the other hand, when the shell properties were higher than the core properties, the opposite was true. Composite impact strength increased with shell thickness increase for all three core systems. However, at a given shell thickness, the impact strength decreased with the addition of SGFs in the shell. Further increase of SGFs in the shell led to somewhat increased impact strength. The structure–property relationship plots provide a design guide for optimizing performance of coextruded WPCs with various combinations of core‐shell qualities. POLYM. COMPOS., 37:824–834, 2016. © 2014 Society of Plastics Engineers