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Publications
Publications (37)
A micromechanical model is presented for tear growth in a cruciform biaxial tensile test of woven fabrics with initial slit-like damage. The size and geometry of the cruciform enter the analysis through dimensionless cruciform size parameters, α and β, representing the distances along the slit normal direction to the central section edge and the cr...
The advantage of utilizing modeling to study fire performance of textiles is the ability to conduct detailed studies of the effect of fabric characteristics on flame spread. First, two textile materials are chosen for modeling that exhibit two limit cases: complete flame spread (nylon 6,6/cotton fiber fabric) and self-extinguish (flame retardant ra...
American soldiers and marines involved in the recent conflicts in Iraq and Afghanistan have suffered increased incidence of burn injury, often as a direct result of exposure to improvised explosive devices. In this work, a one dimensional numerical pyrolysis model for transient heat conduction, incorporating material transformations described by ch...
A series of different experimental techniques were applied to quantify the effects both steady and unsteady pressure differential across a fabric had on the flow through the fabric. Static permeability measurements were made on four common nylon parachute fabrics over a range of fix pressure differentials to provide a baseline for the other techniq...
This paper describes permeability measurements for porous fabrics as influenced by strain, humidity, air flow rate, and fabric elasticity. The focus is on standard parachute fabrics, where the fabric's porosity and air permeability influence the rate of steady-state descent, and also affect the complicated fluid-structure interactions taking place...
Two modeling techniques are introduced to predict the sheet resistance of electrically conductive continuous filament nonwoven fabric: a two-dimensional (2-D) discrete filament stochastic resistor network simulation, and a simple analysis using a laminate analogy. The effects of anisotropy and sample size are considered. Results are compared with e...
Nanofibers formed by electrospinning provide very large surface areas which can enhance material performance in filtration
and product separation. In this work, we explore atomic layer deposition (ALD) as a means to coat and protect electrospun
nylon-6 nanofibers. Exposing nylon to trimethyl aluminum (TMA) during ALD of aluminum oxide results in si...
Nanofibers formed by electrospinning provide large surface areas which enable enhanced material performance in filtration and product separation. In this work, we explore atomic layer deposition (ALD) as a means to encapsulate and protect electrospun nylon-6 nanofibers. Exposing nylon to trimethyl aluminum (TMA) during ALD of aluminum oxide results...
The effect of uniaxial and multiaxial mechanical strain on the electrical conductivity of particle filled polymer composites
is investigated in the framework of concentration-driven percolation. For composites consisting of low aspect ratio, rigid
conductive particles in a compliant polymer matrix, a simple argument leads to the conclusion that the...
Micromechanical models for the interaction between discrete short fibres in idealized bundles are developed and are used to investigate fibre strain profiles, slippage behaviour with increasing extension, bundle load-extension, and tangent stiffness properties. The modeling approach permits abutting fibres to interact by elastic surface shear force...
A variety of commercial woven polypropylene textiles have been found to
have a resistance to ballistic impact that is a significant fraction of the
performance of aramid textiles that have far superior quasi-static mechanical
properties. In this report, the commercialized product, Tegris® (formerly
MFT®), a 100% polypropylene composite made by Mill...
A simple micromechanical model for the deformation of an isolated fiber fragment embedded within a bundle of continuous filaments is used to study progressive fragmentation of the low elongation-to-break (LE) fiber component during extension of a model two-component fibrous structure. The model structure, representing a blended yarn or cord, is rea...
A micromechanical model has been developed that will allow the study of a slit-damaged braided fabric air-beam structure. As such, the relevant system of non-dimensional ordinary differential equations is derived and solutions are given for the stress concentration near the broken yarns. This knowledge will contribute to the prediction of damage gr...
We report the effect of a variable frictional shear force distribution along a slipping broken fiber on the stress concentration (SCF) in blended yarns. Our micromechanical model leads to a system of second order differential equations, which we solve using a convenient eigenvector expansion approach. The results for an exponential variation of fri...
A simple micromechanical model is presented for predicting the onset of tearing at slitlike damage sites in biaxially stressed coated plain weave fabrics. The stress concentration in the first intact yarn at the slit tip is determined as a function of increasing loading, and predictions for the onset of tearing are made under the assumption that te...
Coated woven fabrics are often used as stressed membranes in inflatable and tension structures. When the stressed fabrics in such structures are damaged locally, the damage site often provides a starting point for the propagation of a tear. In this paper, a micromechanical model is developed for predicting the onset of tearing at slit-like damage s...
A simple analytical model for the adiabatic high strain rate extension of synthetic textile fibers is presented. The model suggests that, for fibers with particular thermo-mechanical and constitutive properties, initial nominally uniform strain distributions along the fiber will tend to become non-uniform, with localization of axial strain into a t...
The assumption of a constant friction force (simple slip assumption) on broken slipping yarns, which has been used in the micromechanical analysis of damage growth in stressed plain weave fabrics, is evaluated. In this analysis, the frictional traction on slipping yarns is variable. It starts from zero at the cut end of the yarn and approaches a co...
A previously developed micromechanical model is used to formulate the problem of a blended yarn, consisting of low elongation (LE) and high elongation (HE) fibers undergoing axial extension, with a fiber break in the central region of the hybrid fiber array. A hybrid parameter R, which is the ratio of the axial stiffness of the HE fibers to that of...
A simple micromechanical model is developed for the interactions in a parallel square-stacked mixed array of elastic fibers representing the microstructure of a blended yarn undergoing axial extension. The mixed array consists of a small fraction of relatively high modulus, low elongation-to-break (LE) fibers dispersed among high elongation-to-brea...
Often, fibers with significantly different elongations-to-break are combined in blended yarns. During yarn extension, the low elongation-to-break (LE) fibers undergo a fragmentation process, whereby the LE fibers develop multiple breaks along their length. The interaction between the LE fragments and the high elongation-to-break (HE) fibers is key...
The effect of thermo-mechanical coupling arising from fiber plasticity on the load–extension behavior of continuous filament yarns extended at high-strain rates is investigated using an analytical approach. The plastic deformation behavior of the fibers is assumed to follow a simple constitutive relation incorporating linear thermal softening and l...
A simple micromechanical model is developed for the interactions in a parallel square-stacked mixed array of elastic fibers representing the microstructure of a hybrid yarn undergoing axial extension. The mixed array consists of a small fraction of relatively high-modulus, low-elongation-to-break (LE) fibers dispersed among high-elongation-to-break...
The effect of thermomechanical coupling arising from fiber plasticity on the stability of homogeneous straining deformation in fibers extended at high strain rates is investigated using a simple analytical approach. A constitutive model is assumed for the fiber's plastic deformation, incorporating linear thermal softening and linear strain hardenin...
A simple micromechanical model is used to study the onset of tear propagation at slit-like damage sites (i.e., a series of consecutive aligned yarn breaks) in biaxially stressed plain weave fabrics under increasing load. The method of treating the frictional slip of yarns near the damage site is critical to the success of the model. Although the ac...
A simple micromechanical model is developed for the interactions in a parallel square-stacked mixed array of elastic fibers representing the microstructure of a hybrid yarn undergoing axial extension. The mixed array consists of a small fraction of relatively high-modulus, low-elongation-to-break (LE) fibers dispersed among high-elongation-to-break...
A simple micromechanical model is developed to predict the onset of tear propagation at slit-like damage sites (i.e., a series of consecutive aligned yarn breaks) in biaxially stressed plain weave fabrics under increasing loading. A crucial aspect of the model is the treatment of the frictional slip of yarns near the damage site. Although the actua...
A micromechanics-based mathematical model for a slit-damaged (i.e., a series of consecutive yam breaks), biaxially stressed, plain weave fabric is used to define and motivate a candidate screening parameter pu, which can provide a measure of damage tolerance for a class of such fabrics. Preliminary results are presented from damage growth tests on...
The mechanics of damage of fiber composite sheets has been reviewed, including cases where the analytical models have been compared to experiments. The emphasis has been on the micromechanics approach, where equilibrium of the constituents of the composite lead to appropriate equations for determining stress distributions. The damage mechanisms tha...
A simplified micromechanics approach is used to develop a mathematical model to predict damage growth in prestressed plain weave fabrics near sites where yams are broken. Stress concentration in the yams neighboring yarn breaks is determined as a function of increasing loading. An evaluation of the load redistribution around the damage region inclu...
A structural concept consisting of thin membrane skin panels supported by stiffening ribs is under study for use in tactical shelters designed to withstand airblast. For design analysis it is desirable to evaluate membranes under static loadings in place of more complex and costly dynamic analysis. Previous analysis indicated that membrane panel de...
In recent years inflatable "air-beams," including both woven and braided fabric technologies, have been developed for use in large shelters, inflatable break waters, and space structures. Air-beams are tubular fabric structures which exhibit significant flexural and compressive rigidity when internally pressure-stabilized by air-inflation. Accident...
