The present paper, provides a study of conducting experimental investigations (based on the ISO standards), in the context of determining material properties (mechanical and strength parame-ters) in the case of thin-walled composite structures - made of carbon-epoxy composite. Tests were carried out on 5 different types of test specimens (in accordance with the standards), with a minimum of 9 specimens per each type of test. The tests provided high repeatability of results, and the large number of test specimens per each test made it possible to precisely average the test results in terms of determining the necessary material properties. The tests were carried out using a Zwick Z100 universal testing machine (UTM), under room temperature conditions, using two types of test heads that allow static experimental tests. The results presented in this paper con-stitute a prelude to research within the framework of the project from the National Science Centre (Poland) with the number 2021/41/B/ST8/00148. The paper presents the initial stage of the im-plementation of the aforementioned project - which was the determination of material parameters of the composite material from which the target thin-walled composite structures with closed sections were made.