Improvements in Fabrication of Sand/Binder Cores for Casting

Three improvements have been devised for the cold-box process, which is a special molding process used to make sand/binder cores for casting hollow metal parts. These improvements are: The use of fiber-reinforced composite binder materials (in contradistinction to the non-fiber-reinforced binders used heretofore), The substitution of a directed-vortex core-blowing subprocess for a prior core-blowing process that involved a movable gassing plate, and The use of filters made from filtration-grade fabrics to prevent clogging of vents. For reasons that exceed the scope of this article, most foundries have adopted the cold-box process for making cores for casting metals. However, this process is not widely known outside the metal-casting industry; therefore, a description of pertinent aspects of the cold-box process is prerequisite to a meaningful description of the aforementioned improvements. In the cold-box process as practiced heretofore, sand is first mixed with a phenolic resin (considered to be part 1 of a three-part binder) and an isocyanate resin (part 2 of the binder). Then by use of compressed air, the mixture is blown into a core box, which is a mold for forming the core. Next, an amine gas (part 3 of the binder) that acts as a catalyst for polymerization of parts 1 and 2 is blown through the core box. Alternatively, a liquid amine that vaporizes during polymerization can be incorporated into the sand/resin mixture. Once polymerization is complete, the amine gas is purged from the core box by use of compressed air. The finished core is then removed from the core box

An overview of military textiles

348-352Developments in the weapons and surveillance technologies are prompting innovations in individual protection equipments and battle-field related systems and structures. Besides conventional requirements such as durability to prolonged exposure, heavy wear and protection from external environment, the protection is sought from ballistic projectiles, fire, CBN (chemical, biological and nuclear) weapons and surveillance and detection systems. It is a challenge to the "system" designer to satisfy the conflicting requirements within the constraints of physiological requirements, logistics, technological limitations and the cost. This article gives an overview of the requirements, design considerations, developments and innovations related to the textile usage in the military applications. The examples and citations are mostly in the context of the United States Army

Modeling of elastic, thermal, and strength/failure analysis of two-dimensional woven composites - A review

The usage of textile structures as a reinforcement for polymer composites became essential in many industrial applications in, for example, the marine and aerospace industries because of their favorable stiffness and strength to weight ratio. Determination of elastic properties and failure behavior of textile reinforced composites is vital for industrial design and engineering applications. This paper aims to present a review of numerical and analytical models for elastic, thermal, and strength/failure analysis of 2D reinforced woven composites. Major modeling techniques and approaches are presented. A state Of the art review of woven fabric composites is presented starting from earlier one-dimensional models to recent three-dimensional models. The intention is not to give a detailed analysis of the mathematical approaches to the models discussed, but rather to inform researchers about the main ideas of previous works. This review article cites 122 references

Analysis of a novel 3D hybrid woven/knitted fabric structure - Part I: Geometric model and verification

A novel 3D fabric structure is defined and modeled. The 3D hybrid woven/knitted fabric has a structured that can be categorized in the same group of 3D multiaxial warp knitted structures. The fabric consists of longitudinal yarns in the X direction and two bias yams, which are employed to bind the multilayers of warp yarns on the Z axis with an angle of +/-45degrees without any need for weft yarns. The model of the structure is defined by basic geometric relations using fundamental yarn and fabric characteristics. The geometric model is compared with the experimental results, and the length of each 3D loop, the length of the needle loop, the bias yarn consumption per unit length of the fabric on a single warp yarn, and fabric thickness are verified. Monofilament and multifilament yarns are used for sample production. There is reasonable agreement between theory and experiment, considering the assumptions made and the complexity of the 3D fabric structure. The deviation between the model and experiments is less with monotilament warp yams