The mechanical response of composite structures may be affected by harsh environments, particularly when the matrix has a major contribution, e.g. with off-axis plies. This study aims at investigating the influence of the winding pattern on the axial compressive behavior of filament wound composite cylinder under hygrothermal conditioning. Carbon fiber-reinforced epoxy cylinders were manufactured via filament winding with 1/1, 3/1, and 5/1 mosaic winding patterns and submitted to distilled and artificial seawater environmental conditioning. Water uptake for each hygrothermal conditioning was periodically monitored. The winding pattern influenced both compressive strength and stiffness, and the environmental conditioning decreased strength up to ≈10%. The winding pattern with three diamonds around the circumference of the cylinders provides the properties in term of compressive strength and stiffness.
This work focuses on the viscoelastic response of carbon/epoxy filament-wound composite rings under radial compressive loading in harsh environments. The composites are exposed to three hygro-thermo-mechanical conditions: (i) pure mechanical loading, (ii) mechanical loading in a wet environment and (iii) mechanical loading under hygrothermal conditioning at 40 ∘C. Dedicated equipment was built to carry out the creep experiments. Quasi-static mechanical tests are performed before and after creep tests to evaluate the residual properties of the rings. The samples are tested in (i) radial compression, (ii) axial compression, and (iii) hoop tensile strength. Different laminates wound at off-axis orientations are manufactured via filament winding and analyzed. Key results show that creep displacement is affected by both hygrothermal and mechanical conditionings, especially at a higher temperature. Moreover, residual properties are quantified showing that creep generates permanent damage in the cylinders.
Hybrid composites are commonly applied to obtain tailor-made properties due to additive or synergistic effect between matrix and fibers, yielding a wider range of properties than the use of a single fiber could achieve. The combined use of two or more reinforcements makes the mechanical behavior of hybrid composites more complex, demanding validation of classical micromechanical approaches for the estimate of their properties. The aim of this work is to investigate the mechanical properties of a unidirectional hybrid fibrous composite, at different constituent volumetric fractions, through micromechanical analytical models implemented in the software MECH-Gcomp and through a finite element-based homogenization analysis. An experimental campaign was carried out by producing epoxy composites with glass and carbon fibers via filament winding processing. The samples were submitted to tensile (longitudinal and transverse directions) and in-plane shear tests to obtain elastic moduli, Poisson's ratios and shear moduli of the hybrid composites. Good correlation was found between experimental, numerical and analytical approaches considering the adopted assumptions.
Manufacturing characteristics of the filament winding process, such as the formation of a winding pattern, are usually disregarded in conventional numerical models. However, they could significantly affect stress and strain fields in thin-walled composite shells. This work presents an efficient way to realistically model the filament winding mosaic pattern in composite cylindrical shells under axial compression. The study comprises the linear finite element (FE) Eigenvalue and Eigenvector buckling model of thin-walled composite cylindrical shells using commercial software. A conventional model was developed and an optimization algorithm was used to find the highest Eigenvalue. After the optimum fiber angle was found, it was used for winding pattern drawing and modeling. Three winding patterns were modeled: 1/1, 3/1 and 5/1, where the numerator means the number of diamonds around the number of circumferences indicated by the denominator. The optimum angle-ply fiber layout found was [±30], which reached the highest critical buckling load. The winding pattern influenced the critical buckling load, and the 1/1, 3/1 and 5/1 patterns showed critical buckling loads of 11.237, 11.173 and 11.194 kN, respectively, whereas the conventional modeling approach indicates a critical load of 8.574 kN.
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