In hot and humid climates, air conditioning is an energy-intensive process due to the latent heat load. A unitary air conditioner system is proposed, here, to reduce the latent heat of the humid air using a liquid desiccant followed by an evaporative cooling system. The heat liberated by the desiccant is removed by a solution to the solution heat exchanger. To restore the concentration of the liquid desiccant, the desiccant solution is regenerated by any low-temperature heat source such as solar energy. In order to make the system compact, the membrane heat exchanger is used for the dehumidifier and regenerator. This paper presents the numerical investigation of heat and mass transfer characteristics of a selected membrane dehumidifier under different climatic parameters. Membrane-based parallel-plate and hollow-fiber exchangers are used for this application. A parallel-plate heat-and-mass exchanger (contactor) is composed of a series of plate-type membrane sheets to form channels. On the other hand, hollow-fiber membranes are packed in a shell to form a shell-and-tube heat-and-mass exchanger. The two streams of both contactors are in a counter parallel flow, separated by micro-porous semi-permeable hydrophobic membranes. In this research, the equations governing the transport of heat and mass between the two streams along with the membrane effect in both contactors are solved numerically. The results are compared at different number-of-transfer units (NTU) on the airside and thermal capacity ratios. It is found that the hollow fiber is more efficient than the parallel plate.

As coal has strong adsorption characteristics and well-developed natural fracture systems, an improper choice of fracturing fluid can result in significant challenges for coal bed methane exploitation, including damage to the coal formation and ineffective creation and propagation of hydraulic fractures. Viscoelastic surfactant (VES) fracturing fluid has become a preferred option because of its easy flowback and the resultant minimal damage. A novel nanocomposite fiber with substantially improved functional and structural properties was synthesized by introducing nanoparticles into conventional polyester fiber. Subsequently, a nanocomposite fiber-laden VES (NFVES) fracturing fluid was developed and evaluated in the laboratory. The results show that the fiber disperses well in the fluid and that the addition of a small amount (0.5%) of fiber substantially enhances the proppant-carrying capacity of the fluid. To achieve a proppant-carrying capacity equivalent to a standard VES, the surfactant concentration can be decreased from 2.5% to 1%, which not only reduces costs but also significantly lowers adsorption of the surfactant by the seam and rock surfaces. In addition, rod micelles with less surfactant added are more easily broken. Addition of 0.7% nanocomposite fiber reduced the tube friction by 20% at shearing rate of 5000 s −1 . The nanocomposite fiber also effectively prevents backflow of the proppant and mitigates leak-off of fluid and aggregation of coal scraps. Continuous degradation of the fiber occurs over time at formation temperatures, thus reducing the potential damage to the coal seam. The strong performance of this NFVES fracturing fluid in the laboratory evaluations indicates the great potential and development prospects for coal bed methane reservoir stimulation using this fluid.

Wind turbine blades undergo fatigue and their performance depletes as time progresses due to the formation of internal cracks. Self-healing in polymers is a unique characteristic used to heal the cracks inherently as they form. In this study, a new method is demonstrated for supplying the monomer (that is quintessential for the healing process) uniformly throughout a fiber reinforced polymer composite. Commercial tubes were used to produce a vascular network for increased accessibility of the healing agent. The tube layouts were varied and their effect on the composite structure was observed. Conventional glass fiber reinforced polymer matrix composites (PMC) without microtubing were tested using dynamic mechanical analysis (DMA) to study the flexural visco–elastic behavior. The vascular network arrangement coupled with DMA data can be used to uniformly supply appropriate amount of healing agent to implement Self-healing in fiber reinforced PMC.

A method for investigating the dynamic response of shear deformable laminated composite plates subject to low-speed impact is presented. The equations of motion of the impactor and the plate are derived via a virtual work approach. The contact force between the impactor and the plate is calculated by using an experimentally established contact law. The effects of existing in-plane forces, plate aspect ratio, length-to-thickness ratio, fiber angles, and number of layer groups on the contact force with or without the consideration of ply failure are studied. Optimal fiber angles and number of layer groups for angle-ply plates with maximum first-ply failure impact velocity are determined based on the maximum stress criterion.

The homogenizing scheme of Ferrari and Johnson yields the effective elasticities of short-fiber composites with arbitrary orientation distributions. As a foundation for the relative numerical analysis, their homogenizing scheme is here recast in the space of invertible 6×6 matrices with an appropriate operation. Averaging procedures for isotropic-isotropic composite with nonunidirectional transversely isotropic fiber orientation distributions are presented.

The mechanical response of a two-dimensional fiber-composite system is considered with the inclusion of the microstructure. The material system is seen as a viscoelastic matrix which contains a layer of randomly oriented, short elastic fibers. In this approach, the mechanics of the discrete microstructure introduce the relevant field quantities as random variables or functions of such variables and their corresponding distribution functions. The analysis is presented in a general form and could be applicable to a large class of randomly structured composite systems.

The self-ignition and smoldering characteristics of cellulosic materials, as exemplified by cotton fibers, when subjected to convective low-velocity heated air stream were studied experimentally at atmospheric pressure. The effects of the content of moisture in the raw cotton on its ignition delay and smolder front propagation rates were established. Some comparative tests were also conducted on dry cotton samples containing instead of moisture, various concentrations of n-hexane or an alcohol mixture.

An experimental test program is described in which biaxial failure envelopes were generated for unidirectional [0] 8 and quasi-isotropic [0/+45/90/−45] s specimens made from Toray T800HY/3910 graphite/epoxy. Data was generated in all four quadrants of the biaxial stress plane. Fiber direction failure strengths were also found by uniaxial tension and compression tests. The quasi-isotropic compressive failure strengths are approximately 50 percent of the tensile strengths. Failure strengths in the tension-tension quadrant were essentially the same as previous tubular specimen tests made of a similar material (Swanson and Christoforou, 1986) indicating that free-edge and stress concentration effects may not preclude using flat cruciform specimens to generate biaxial failure data.

The objective of this study was to gain a better understanding of the low-velocity impact phenomena of composite pipe. The focus was on test method development, and material and damage characterization. A drop weight tower tester was designed in this investigation. The dynamic tests were conducted using three different impactor geometries, velocities, and masses. It was found that the damage was localized and on the outer surface of the pipe in the case of the conical and wedge tip impactors. On the other hand, the damage zone was larger than the impact zone for the hemispherical impactor, and cracks were first seen within the inner surface of the pipe. This implies that the hemispherical tip impactor caused more damage to the pipe than the conical or wedge tips. The energy absorbed slightly increased with an increase in velocity or in mass. The contact period for the conical impactor was the longest. The velocity and mass of the impactor had only a slight effect on that period. The wedge impactor generated the largest peak force. The energy absorbed by the two composite pipes under low-velocity impact was studied. The specimen-1, Derakane 411-45 resin with less glass fiber, seemed to absorb more energy compared to the specimen-2, Derakane 470-36 resin with more glass fiber. In addition, the specimen-2 exhibited a slightly higher maximum impact force. Therefore, impact response is sensitive to fiber content.

The design of composite rotors for high-energy density pulsed power supplies demands accurate characterization of both the mechanical and electrical properties of fiber-reinforced epoxy. The mechanical properties of S-2 glass-epoxy, IM6 graphite-epoxy, and hybrid graphite-glass epoxy composites were measured in tension and torsion tests, providing strength and stiffness parameters for rotor dynamics modeling. Variable frequency electrical resistivity tests were conducted to allow estimation of eddy current losses arising in carbon-reinforced materials. Volume fraction measurements using electron microscopy and analysis by digestion allow for normalization of the test results with respect to composite fiber content. The experimental results were used to evaluate the micromechanical rule of mixtures and Halpin-Tsai correlations.

An analysis model is presented to analyze continuous fiber-reinforced composite structures with some local damage such as matrix cracks. Two separate material properties of fiber and matrix are used in the analysis model instead of a smeared-out global anisotropic material property. Stresses acting on fibers and stresses acting on matrix are computed directly. If there are local matrix cracks in the direction perpendicular to the fiber orientation in a composite structure, the broken matrix is modeled not to sustain any tensile stress in the fiber direction. A finite element formulation is derived for the analysis model. Some numerical problems are presented to test the proposed analysis model.

Toughening of ceramics by incorporating strong fibers has become an established technology, resulting in the creation of a new generation of tough ceramic composites. This toughening effect is primarily due to bridging of the crack surfaces by intact fibers when the composite is subjected to tension. The fiber bridging mechanisms, which are contingent upon the stress transfer phenomena between the fiber and the matrix, are reviewed in this paper. The critical role of the properties at the fiber/matrix interface in controlling the stress transfer phenomena is examined. Finally, evaluations of the interfacial properties of the composite by the indentation technique and the corresponding analysis are presented.

Response of a cylindrical panel made of layers of composite material and subjected to in-plane loads is investigated. Prebuckling deformations are determined for antisymmetric angle-ply and cross-ply panels having simply supported boundary conditions. Buckling solutions are obtained via the Rayleigh-Ritz method. Nonlinear programming is used to optimize the designs. Design variables are taken as fiber orientations and/or thicknesses of different layers. Numerical results are presented for different materials and different geometrical parameters, including aspect ratio and curvature-to-length ratio.

The problem of an infinitely long orthotropic strip containing a pair of coplanar cracks perpendicular to the edges of the strip is studied. The surfaces of the cracks are loaded by an arbitrary pressure, while the edges of the strip are free from tractions. The solutions to the problem is written in terms of two potential functions. The mixed boundary value problem is reduced to a Fredholm integral equation of the second kind by using the techniques of Fourier transform and the finite Hilbert transform. In the special case of a uniform opening pressure, exact expressions for the stress intensity factors at the inner tips and the outer tips of the cracks as well as the shape of the deformed cracks are obtained. Numerical calculations for a fiber-reinforced composite are carried out to study the interaction between cracks, the existing stress-free edges, and the effect of the direction of the reinforcement fiber on the various quantities of interest in fracture mechanics. The cracks are either parallel or perpendicular to the reinforcement fiber.

Thin-walled structural members are used extensively in the offshore industry in applications ranging from marine risers to platforms and frames. Advanced fiber composite structural members may offer advantages over their conventional steel counterparts in certain situations. Use of composite members will require modifications to existing structural analysis codes. This paper presents a beam theory for thin-walled composite beams that can be incorporated into existing codes. Timoshenko beam theory is utilized to account for shear deformation effects, which cannot be neglected in composite beams, and for the variability in material properties in different walls of the beam cross section. The theory is applied to the analysis of the free vibration problem and shows the dependence of the natural frequencies and mode shapes on the in-plane properties of the laminates that form the walls of the beam. Forced periodic and forced arbitrary problems are also discussed and the deflected shapes and maximum deflections are shown as functions of wall layups.

A theory has been developed for the analysis of fiber-core wire rope with multilayered strands. The rope is subjected to both an axial force and an axial twisting moment. The previously developed linear theory for helically shaped wires is used and the equations governing compliance of the fiber core are formulated in a linear fashion. The resultant linear equations are easily solved. The theory is applied to a 6 × 19 Seale fiber-core wire rope and dimensionless results are presented. A load-deformation curve for a Seale fiber-core wire rope is obtained experimentally. Both the theoretically predicted effective modulus of elasticity and the predicted effective Poisson’s ratio of the rope compare favorably with the experimental results.

The problem of the bending of a spiral strand or armored cable is addressed, with particular reference to the “free bending” situation where pulleys or other restraints are absent. The analysis, based on a study of the properties of the layers of wires which form the strand (or armor), treats the “free field” bending, remote from the termination. A parallel treatment of the situation close to a termination is summarized. In the former case, limiting values for the effective bending stiffness of the strand are presented; in the latter case an examination of the behavior of an outer layer of wires sliding (with known frictional characteristics) over an inner core has led to predictions of the strains and movements between the individual wires and the inner core (as a function of wire position in the strand) which are reported in the paper. The results offer an explanation of some experimental observations from fatigue tests on a large (39mm) strand under combined steady axial load and lateral movements causing bending adjacent to the restrained termination. In particular the observed wire failures close to the socket, not at the extreme fiber positions but at the neutral axis, can be explained in terms of the much larger slip on the interlayer contact points there.