20: 2 (2020) 51-59 ISSN: 2084-6096 ISSN (online): 2299-128X Grażyna Ryzińska*, Grzegorz Janowski Rzeszow University of Technology, al. Powstańców Warszawy 12, 35-959 Rzeszów, Poland *Corresponding author. E-mail: grar@prz.edu.pl Received (Otrzymano) 26.05.2020 INFLUENCE OF RVE GEOMETRICAL PARAMETERS ON ELASTIC RESPONSE OF WOVEN FLAX- -EPOXY COMPOSITE MATERIALS In the case of polymer composites reinforced with natural fiber woven fabrics, microstructural calculations are extremely difficult to perform due to their characteristic variability, among others their mechanical properties. The aforementioned scientific problem has not been thoroughly investigated, hence the purpose of this work was to assess the possibilities of predicting the properties of a composite reinforced with flax woven fabric by micromechanical calculations using the Mori- -Tanaka and the double inclusion homogenization models. In addition, the second important utilitarian problem that was undertaken in the work was assessment of the impact of the size of the representative volume element (RVE) on the obtained results. The analyses were carried out for composites based on epoxy resin reinforced with flax fabrics: plain, 2x2 twill and 3x1 twill types. Based on the performed calculations, it was found that the obtained results depend on the type of weave in the fabric used, the size of the RVE, the number of yarn bands in the RVE and the appropriately selected homogenization method. Guidelines useful for evaluating the optimal RVE size depending on the type of weave were formulated. Keywords: RVE, natural fiber composites, Digimat, flax, FEM, homogenization WPŁYW PARAMETRÓW GEOMETRYCZNYCH W REO NA WŁAŚCIWOŚCI SPRĘŻYSTE MATERIAŁÓW KOMPOZYTOWYCH ŻYWICA EPOKSYDOWA-TKANINA LNIANA W przypadku kompozytów polimerowych zbrojonych tkaninami z włókien naturalnych przeprowadzanie obliczeń mikro- strukturalnych jest wyjątkowo trudne do wykonania z uwagi na charakterystyczną dla nich zmienność, m.in. właściwości me- chanicznych. Wspomniany problem naukowy nie jest dokładnie zbadany, stąd celem niniejszej pracy była ocena możliwości prognozowania właściwości kompozytu wzmacnianego tkaniną lnianą poprzez obliczenia mikromechaniczne z wykorzysta- niem modelu homogenizacji Mori-Tanaka oraz Double Inclusion. Ponadto drugim istotnym problemem utylitarnym, który podjęto w pracy, była ocena wpływu wielkości reprezentatywnego elementu objętościowego (REO) na uzyskane wyniki. Ana- lizy przeprowadzono dla kompozytów o osnowie żywicy epoksydowej zbrojnej tkaninami lnianymi o splocie: płóciennym, sko- śnym 2x2 oraz skośnym 3x1. Na podstawie przeprowadzonych obliczeń stwierdzono, że uzyskane wyniki zależą od rodzaju splotu w zastosowanej tkaninie, wielkości REO, ilości pasm przędzy w REO oraz odpowiednio dobranej metody homogeniza- cji. Sformułowano wskazówki przydatne do oceny optymalnego wymiaru REO w zależności od rodzaju splotu. Slowa kluczowe: REO, kompozyty wypełnione włóknami naturalnymi, Digimat, len, MES, homogenizacja INTRODUCTION In the process of modeling composite structures, it is very often impossible to perform calculations for the entire structure due to limitations in the performance of computers and the relatively long calculation time. Therefore, it is desirable to describe the whole structure with a much smaller area that remains large enough to be constitutively valid. This area, which is small enough on the one hand, and large enough on the other, is referred to as the representative volume element (RVE). Basically, applications assume that the RVE exists and that its size is predetermined. However, de- termining the size of the RVE is often one of the main questions to be answered. This problem has not been sufficiently discussed in the literature, with notable exceptions [1, 2]. After a positive answer to the question about the definition of the RVE, a procedure for determining its size should be introduced. There have been several attempts in the literature to develop a procedure to es- tablish a representative volume [3-5]. An objective method of determining the RVE size was also proposed in the work of Gitman et al. [6]. This method is based on combined statistical analysis of the numerically modeled responses of the material.