EFFECT OF REINFORCEMENT PARAMETERS ON THE STRESS–STRAIN STATE OF POLYMER COMPOSITE MASTS

Abstract

The aim of the study is to optimize the structure of a polymer composite with continuous longitudinal reinforcement for lighting masts by numerically simulating their stress–strain state under extreme wind loads.
A three-layer composite mast (epoxy matrix reinforced with fiberglass or carbon fiber) with an outer diameter of 90 mm, a wall thickness of 5 mm, and a height of 4 m was investigated. A comparison with the base aluminum structure (6060-T6 alloy) was performed using finite element analysis (FEA) in the Ansys software suite. The combined effect of storm wind (25 m/s), lighting device mass (5 kg), and aerodynamic pressure was taken into account. The volume fraction of fibers (40, 60, 80%) and the spatial location of the reinforced layer (inner, central, outer) in the cross-section were varied.
The use of polymer composites reduces the mast mass by 50–52% compared to the aluminum analogue (14.42 kg). Replacing fiberglass with carbon fiber additionally reduces the mass by ~10%. Increasing the fiberglass volume fraction from 40 to 80% increases the mass from 6.70 to 7.86 kg, reducing the maximum displacements of the mast top from 4.04 to 3.51 mm. The configuration with a reinforced inner layer provides the highest stiffness: deflections are 2.02–2.04 mm, equivalent stresses are 1.11–3.42 MPa, and the factor of safety reaches a maximum of 704–824. Reinforcing the outer layer increases equivalent stresses up to 5.22 MPa and reduces the factor of safety to ~260. Carbon fibers generate higher stresses (up to 5.22 MPa versus 3.03 MPa for fiberglass) due to a higher modulus of elasticity and local load concentration. Their higher strength limits (up to 2407 MPa) provide an average factor of safety (~575) close to that of fiberglass. The base aluminum mast has the smallest deflections (0.07 mm) but a significantly lower factor of safety (214). A structure with fiberglass in the inner layer at a volume fraction of 60–80% was determined to be rational for street lighting.
The patterns of local stiffness redistribution in tubular composite elements depending on the configuration of longitudinal continuous fibers were established. The possibility of targeted control of the mast strength without changing its geometry was proven, which is implemented in serial production using the developed direct extrusion technology.