A multilayer composite structure is disclosed. The multilayer composite structure has at least one polymer-based cap layer containing, for example, an acrylic, styrenic or acrylonitrile polymer and at least one polyester-based inner or substrate layer. Also disclosed are methods of forming the multilayer composite structure to improve and control the level of adhesion between the layers. Optional tie layers can be used to improve and control the level of adhesion between the layers. An optional exterior layer over the cap layer can contain polyvinylidene fluoride (PVDF) polymers. The multilayer composite structure combines the attributes of both polymers—the high UV stability, scratch resistance, and excellent appearance of the polymer-based outer cap layer and the strength and impact resistance of the polyester-based interior layer.