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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, INTRODUCTION Resin transfer molding (RTM) is an attractive manufacturing process for composites. It provides many advantages for industrial processes: relatively low costs, reduced processing time, and ability to produce complex [...]

The theory of consolidation has its origin in the effective stress concept developed by Terzaghi, which was derived based on several assumptions to arrive at a simplified theory. Considering the limitations involved in Terzaghi's theory, various attempts are being made by researchers to idealize the problem to represent various field situations. This paper presents a more generalized theory for vertical consolidation of a compressible medium of finite thickness, subjected to suddenly applied loading, assuming small strain and no creep. The theory assumes small deformations, and thus the settlement is governed by vertical strains generated by an increment of loading, neglecting the effect of self-weight of the soil. The analytical solution presented here takes into account e-log K and e-log [sigma]' linear responses under instantaneous loading. With [C.sub.c] as the slope of the e-log [sigma]' line and M the slope of the e-log K line, a parameter [C.sub.c]/M is identified which is found to govern the rate of consolidation. In this paper, an analytical closed form solution is obtained for vertical consolidation considering the variation in the compressibility and permeability. CE Database subject headings: Consolidation; Clays; Permeability; Compressibility; Strain.

Effective medium theory (EMT) was employed to estimate permeability of fine-grained estuarine sediments. X-radiographs were taken of sediment cores collected in the field and from laboratory aquaria, designed to mimic the benthic environment of an estuary. Image analysis of two-dimensional X rays provided values of pore parameters required by the EMT model, which include pore body and throat radii, pore throat length, porosity, and the interconnectivity of pores. Values of these parameters were used to quantitatively calculate permeability based upon Darcy's law. The EMT model with an arithmetic mean for averaging pore parameters predicted permeability 1 order of magnitude higher than measured values. The harmonic mean for averaging pore parameters in the EMT model provided estimates of permeability similar to measured values. DOI: 10.1061/(ASCE)0733-9429(2002)128:11(1002) CE Database keywords: Darcy's law; Estuaries; Imaging techniques; Marine clays; Numerical models; Permeability; Permeameters; Sediment.

The material parameters to express the degree of discontinuity of hydraulic gradient in the developed model (Part I) are calibrated based on the sensible analysis of the experimental results, and then the applicability of the calibrated parameters is discussed. As a result, the material parameters are calibrated by the sensible analysis, and then its relevance can be confirmed by another experiment. Moreover, it can be seen that the normalized permeability of concrete as a nonhomogeneous material by the initial permeability (homogeneous material) can be regressed with three straight lines in the crack width axis with the logarithm. Then the intersection point at the crack width axis shows the critical width at which leakage will not occur. The intersection point at the last two straight lines shows the critical Reynolds number at which flow becomes laminar to turbulent according to the experimental result.

A mathematical model for water migration in concrete that changes from a homogeneous to a nonhomogeneous material due to its loading history is developed in detail. In the proposed model, concrete is assumed to be composed of aggregate, cement paste, water, a crack band, and an interfacial crack between the aggregate and cement paste. The discontinuities for displacement and hydraulic gradient on cracks are considered on the microlevel. Then the governing equation for water migration in concrete as a homogeneous and a nonhomogeneous material is developed by coupling the mass conservation law and the force equilibrium. Therefore, it is possible to apply the developed model not only to cement-based material but also to porous permeable material like soil material and rock. However, the applicability of the developed model must be confirmed by comparing the experimental results.

We have investigated porosity and permeability damage around perforations using a combination of transient analysis and X-ray CT. The method applied allowed us to perform the entire experiments on samples under simulated in-situ stress conditions and to map variations in permeability along the length of the core as well as with radial distance from the perforation. Berea (10.2-cm (4-in.) dia) cores saturated with low-viscosity silicone oil were perforated using conventional-shaped charges (6-g HMX) and API RP43 procedures by using 6.88-MPa (1000-psi) effective stress and 5.16-MPa (750-psi) and 2.61-MPa (350-psi) underbalance. Low-permeability Torrey Buff Sandstone was also perforated using 5.16-MPa (750-psi) underbalance. After sufficiently flowing the perforations, higher-viscosity silicone oil was injected. The movement of fluids was tracked using X-ray CT to measure the local velocity of the viscous fluid front at different locations along the perforation. Results of these tests were compared in terms of permeability and porosity damage. Quantitative analysis on Berea cores show, for the specific charge and test conditions used, that damage extends approximately 2 cm (0.78 in.) from the center of the perforation. Comparison of tests performed with 2.41-MPa (350-psi) and 5.16-MPa (750-psi) underbalance show a clear increase in permeability near the tunnel wall at the higher underbalance. A zone of somewhat-reduced permeability exists at approximately 1.7 cm from the perforation center in the latter case. Porosity profiles calculated show that porosity is almost uniform out from the tunnel and there is no compacted zone near the tunnel wall in liquid-saturated cores. However, there is a high-porosity zone from the tunnel wall out about 2 mm. This may be due to a region of circumferential partings and small cracks that lead to high porosity or due to the possible artifacts discussed in the paper. Qualitative results have also been obtained for a tight sandstone for which underbalance was insufficient to remove debris from the perforation tunnel. CT images reveal that the plugged tunnel acts as a conduit for fluid flow, showing that the plugging material has significantly higher permeability than the surrounding rock.