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

Abstract

The mechanical properties of composite structures depend on the preform impregnation and a successful impregnation can be achieved using the permeability relation in the case of an infusion process. The objective of this study is to develop an analytical model to predict the permeability K of carbon and glass fabrics through hybrid laminate using different stacking sequence, applying an average-permeability model. Preforms permeabilities were evaluated through tortuosity and void-volume fraction. The model allows the analysis of different stacking sequence combinations (interleaved and in block), measuring the contribution of each material type. As a result, hybrid average-permeability model was validated through experimental permeability tests, dimensionless permeability, and tortuosity results, besides enabling predictions of the flow front behavior with <10% of deviation. Carbon fiber preforms exhibited higher flow resistance, which is explained via tortuosity concept. A combination of carbon/glass preforms presented an increased permeability, which means a synergy that provides higher value of K. In addition, the use of hybrid preforms, especially Hybrid 2 stacking sequence, reduce the injection time and void formation, ensuring composite impregnation quality. POLYM. ENG. SCI., 59:1215-1222, 2019

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

“…Table 4 presents composite laminate physical characteristics, in which the density presented the same magnitude as the literature. 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.…”

“…However, noise (non-controllable) can be attributed to intrinsic heterogeneity of a composite, void content, resin-rich regions occurrence, fiber misalignment, lack of fiber filament, among other factors which result in fluctuation response. 25 The presence of two tests (creep/recovery and stress relaxation) and three parameters for each test resulted in two orthogonal matrices, one for each test. Three levels were chosen, Level 1 (considering glassy region), Level 2 (considering rubber region), and Level ½ (considering glass transition region).…”

“…However, noise (non-controllable) can be attributed to intrinsic heterogeneity of a composite, void content, resin-rich regions occurrence, fiber misalignment, lack of fiber filament, among other factors which result in fluctuation response. 25…”

Creep behavior of polyetherimide semipreg and epoxy prepreg composites: Structure vs. property relationship

“…4 As a matter of fact, the higher packing capability of carbon fibers results in higher resistance to the percolation of the matrix by a porous media than glass fibers, and this phenomenon was already observed in previous studies. [20][21][22][23] The plain weave also increases tortuosity of the flow and decreases the impregnation velocity, promoting more porous regions for preforms that require longer impregnation time -due to the high resistance of the medium to flow. 20 On the other hand, the absence of dry state for epoxy system (prepreg) combined with the lower and tortuosity space between carbon fiber tow induced higher void formation for carbon fiber/epoxy through trapping air and volatiles generated during processing.…”

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.…”