FOLDING TECHNIQUES AND ITS IMPLICATIONS ON FABRICATION OF INFLATABLE MILITARY DECOYS

Abstract

Folding techniques plays a very important role in fabrication of inflatable structures. It ensures compact stowage and lightweight structure thereby making it portable to use. Folding technique selected for fabrication of inflatable structure is supposed facilitate the structure in faster deployment and also should not affect the life of the structure. FEM modelling and analysis is done on Inflatable structure model for folding to get compact shape using ABAQUS. The material used in making inflatable structure/decoy is supposed to have high strength and the coating used on the fabric is of PVC. The PVC coating makes the fabric durable, waterproof, fire retardant and resistant to external environmental factors. The adhesion strength between the PVC coating and resins is also one of the important factors in selecting fabrics for inflatable structures. Uni-axial tension test and Bias-extension test is carried out in UTM to find the mechanical behavior of the fabrics. Upon testing the fabrics for the application, we found double sided PVC coated polyester to be most suitable for our work. FEM modelling is done on Inflatable structure for inflation and deflation using indirect method by means of inflow of air (ideal gas) in ABAQUS. We have used two methods in fabricating the models (i) PVC welding using heat gun (ii) Adhesive(dendrite). Three box models were prepared to carry out analysis of bulging in structures (i) Simple Box Model (ii) Box Pipe Model (iii) Box with Internal Baffles Model. Both the fabrication techniques were utilized in making the model based on part size and applicability. All three models were fabricated and compared in lab in terms of fabrication methodology, weight, leakages, bulging effects and folding methodology. It is concluded upon comparison that overall Box with internal baffles is the most suitable model to be used for inflatable military decoy structure. Simple zig-zag method for folding the inflatable structure into double fold gives best appropriate result for inflatable structure. Keywords: Inflatable military decoys, folding techniques, FEM modelling in ABAQUS, Indirect Method for inflation in ABAQUS, uni-axial tension test and bias-extension test. PVC welding and adhesion, bulging effects.