In this work is presented an empirical developed model for materials substitution: An empirical established quantity of a fiberglass reinforced polyester composite (basic material) was substituted successively with two natural cheaper materials (natural wastes) resulted from other manufacturing processes. The experiment is purely empirical and no theory is developed in this work. The main scope is to observe if the new and cheapest materials can successful replace the much expensive basic materials in some industrial applications. The microstructures and some physical and mechanical properties of the new materials were studied by reporting to the basic material. © The Authors, published by EDP Sciences.