This paper aims at determining the mechanical properties such as Poisson ratio, biaxial modulus, and residual stress of polymer membranes using the bulge test and fringe projection. Under this idea, a bulge test apparatus has been developed for robust usage, under the room temperature, in industrial environments that are usually noisy and full of all kinds of vibrations. A setup of the bulge test, consisting of single chips and digital on-off valves, was used to achieve automatic precision control of pressure application to gas chamber with a circular polyimide (PI) test film fixed on the opening of it. A deformed image was then obtained via fringe projections with a series of optical apparatuses, and a 3D membrane deformation distribution was further achieved from this deformed image by some image processes that are chiefly through wavelet transformation and phase expansion. With the measurements of maximum membrane deformation versus applied pressure and given the Young’s modulus of test membrane, we could further calculate the Poisson ration (and then biaxial modulus) and residual stress of the film. Also, the measurements were validated to be highly accurate by comparison with a finite element analysis.
In this research, the epoxy resin was reinforced by (16 layers) of E-glass fiber woven mat (0^°/90^°) with 50% weight fraction and total thickness (3mm). Using 16 layers was due to the absence of any previous study that used this number of layers at this thickness. It is considered a modern study of this style because of the rapid development in modern engineering industries that required lightweight composite materials with high strength and small thickness, which are used in the aerospace industry aviation and other precision engineering industries. The composite material was cut into angles (0^°,5^°,15^°,30^°,45^°) by using CNC water jet culling machine. The tensile test was used to determine the strength of a material ratio to the fiber's direction and by using Vickers hardness to determine the hardness of composite and pure epoxy. The result of pure epoxy (matrix) has the lowest value in tensile strength (σ_UTS), Yong's modulus (E), 0.2% proof yield stress (σ_(0.2%)), modulus of toughness and toughness when compared with a composite material with adding 16 layers of "E-glass fibers". The direction of the fibers with (5^°) of composite has the highest strength, Young's modulus, and 0.2% proof yield stress when compared with (0^°,15^°,30^°,45^°) and pure epoxy. The improvement strength (10.8, 11.8, 9.8, 8.5, 8.3 times) at (0^°,5^°,15^°,30^°,45^°) respectively when compared with pure epoxy. The hardness of composite material improved (220%) relative to pure epoxy. The results show that the best improvement of composite material with fiber's angle (5^°) has the highest results compared with pure epoxy.
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