Mechanical behavior simulation: NCF/epoxy composite processed by RTM

Abstract

Considering aeronautics requirements, academies and industries are developing matrixes and reinforcements with higher mechanical performance. The same occurs with the process where new studies focus on obtaining composites with suitable matrix/reinforcement interface. The use of epoxy resin and carbon fiber with high mechanical performance does not guarantee a composite with high mechanical properties, considering imperfections and void formation along the laminate in case of inappropriate processing parameters. The aim of this article was to analyze and quantify the mechanical behavior of polymer composite reinforced with continuous fibers using finite element methodology and postprocessing software simulation. In addition, the classical laminate theory and finite elements were used to simulate flexural and tensile tests of composite specimens. Simulation results were compared with experimental test results using a carbon fiber noncrimp fabric quadriaxial/epoxy resin composite processed by resin transfer molding. Although void volume fraction for structural materials presenting results under aeronautics requirements regarding of 2%, imperfections like lack of resin and impregnation discontinuity showed an influence in tensile and flexural experimental results. Experimental mechanical behavior decreased 10% of strength, in comparison with simulation results due to imperfection on impregnation measured by C-Scan map. Improvement in processing procedures could able to provide greater impregnation continuity, reducing defect formation and ensuring better matrix/reinforcement interface. As a final conclusion, the process plays a role as important as the characteristics of reinforcement and matrix and, consequently, the mechanical properties.

Hybrid‐permeability model evaluation through concepts of tortuosity and resistance rate: Properties of manufactured hybrid laminate

“…This processing technique mainly aims at its usage in the aeronautical field, where carbon fabrics with a fiber volume fraction of at least 50% and maximal void‐volume fraction of 2% (for a high degree of reliability) are employed (requirements for structural applications) . Industrial applications also require a homogeneous distribution of matrices throughout the reinforcement . An unsuccessful distribution causes dry spots and voids, which are detrimental to the mechanical properties of composites .…”

“…Industrial applications also require a homogeneous distribution of matrices throughout the reinforcement . An unsuccessful distribution causes dry spots and voids, which are detrimental to the mechanical properties of composites .…”

Creep/recovery and stress-relaxation tests applied in a standardized carbon fiber/epoxy composite: Design of experiment approach

“…25 Fiber volume fraction was higher than 50%, thus challenging impregnation behavior with higher reinforcement volume, as evidenced by high void content (3.44%) when compared with the literature. 1,27 The standard deviation in Table 4 showed small variation, which implies a lower composite heterogeneity. This fact is strongly supported by considering different parts of the laminate in which the analysis was performed.…”

“…Mechanical property is a fundamental response for structural composite applications. Tensile and flexural, 1 interlaminar shear, 2 and crack propagation 3,4 are among the more frequently used tests regarding polymeric composite materials. Other mechanical properties studied are creep, 5,6 recovery, 7,8 and stress relaxation.…”

Porosity Characterization of Carbon Fiber/Epoxy Composite Using Hg Porosimetry and Other Techniques

“…The control of pore formation in a polymer composite is dependent on a successful infusion process, particularly in the case of materials for primary structural applications . Void formation occurs as a result of a number of factors including air trapped within the polymer matrix, bubbles in the resin during injection, moisture in the matrix, and inadequate process parameters . According to Etemadi et al , the void volume fraction is the term commonly used in the literature as a measure of the proportion of voids present in relation to the total composite volume, along with the porosity, which relates to the amount of pores.…”