Abstract: 【Objectives】In order to investigate the effects of various GF contents in the shell layer and shell thickness changes on thermal expansion and flexural properties of coextruded WPCs. 【Methods】Co-extruded WPCs with short glass-fiber(SGF)loaded shells were manufactured, the formulations for the two-core systems and three shell thicknesses(i.e., 1.0, 1.2 and 1.6 mm)were used to make different shells. Their flexural and thermal expansion behavior was studied. It was shown that the LTEC values varied with composite structure and composition(i.e., core,shell thicknesses and materials). 【Results】The use of SGF-filled shells helped lower overall composite LTEC values. The imbalance LTEC between core and shell layer, and their modulus caused complex stress fields within a given composite system. Extruding a relatively thick, less-stiff HDPE shell with a large LTEC value over a stiff and thermally. Stable WPC core decreased overall composite modulus and increased the LTEC values. The composite modulus and strength increased and LTEC values decreased with increase of the SGF loading levels in the shell. 【Conclusions】The flexural modulus/strength of core-shell structure WPC was greatly enhanced with unfilled-and filled HDPE shells.