Modelling of Bending Pre-compressed Beams Made of Resin L285

Composites, due to their functional properties, are becoming more and more popular in many industries. Appropriate strength parameters are obtained by defining the warp and reinforcement constituting their structure. This article analyzes a composite consisting of polyamide reinforcement and L285 epoxy resin. The results of experimental studies have been compared with the results of computer simulation, using the finite element method (FEM). Material L285 resin has an aviation approval and it is characterized by high static and dynamic strength. The reinforcement has been made of polyamide yarns (with the Ares 20 trademark) characterized by increased breaking strength, high resistance to abrasion and the influence of external factors. The testing program assumed making standard specimens without reinforcement and specimens with reinforcement which were subjected to initial stress equal to 25% of the breaking load. Such actions made it possible to compress the resin constituting the warp and introduce, in a controlled manner, the initial load counteracting the forces coming from external loads. Reinforced specimens have been subjected to bending, determining the deflection arrow, while non-reinforced specimens (standard specimens) and polyamide yarns have been subjected to a tensile test, thanks to which their Young modules have been determined. Knowing the value of longitudinal elastic moduli and Poisson coefficients of resin and polyamide yarns (based on the literature), it was possible to assess the differences between the numerical model and real composite specimens and thus determine whether the model has been correctly made.