| This work describes research aimed to probabilistically assess the mechanical properties of a pultruded fiber-reinforced polymer (FRP) reinforced with a 3D braid and roving. In addition, reliability-based reduction factors for the design of such materials are developed and proposed. Elastic moduli are investigated because the design of most civil engineering applications is dominated by serviceability and buckling limit states rather than the strength. To posses a certain level of confidence in these value estimation, it is necessary to fully explode the material applications. This methodology combines simplified classical lamination theory in one case and a 3D model (Fiber Inclination Model) for braid preform in another case with experimental values in a probabilistic model to simulate the randomness of the system by the Monte Carlo technique. The accuracy of the theoretical model is investigated, evaluating the coupling effect caused by the variations in contituents and fiber orientation. Randomness is considered beginning at the micromechanical level (fiber/matrix) up to the macromechanical level (ply mechanics). All fibers were E-glass embedded in vinyl ester matrix. Reduction factors for the material are suggested providing at least a 95 % confidence level. Parametric analysis were performed evaluating the effect in the material properties by a variation of the mechanical properties (Ef, Em) at micromechanical level, the fibers orientation (theta), and the fiber volume fraction (nu f). The proposed reduction &phis; factors for the stiffness design of the pultruded material reinforcement with a 3D braided textile are &phis; x = 0.50 and &phis;y = 0.75. The parametric analysis indicated that the fiber orientation and the fiber volume fraction are the variables that mostly control the variability of the material. |
