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This paper describes an optimum structural design of a CFRP isogrid cylindrical shell using a genetic algorithm (GA). When the CFRP isogrid cylindrical shell receives a prescribed uniaxial compressive load, an objective is to minimize weight of the CFRP isogrid cylindrical shell subjected to the constraint conditions of no buckling and no material failure. The buckling and material failure loads were approximated by a response surface method combined with partitioning of design spaces and these approximated values were used in the process of GA instead of FEM calculations in order to reduce the computational time. Furthermore, the differences from the constraint conditions of the linear or the non-linear (local) buckling loads were also calculated and their results were compared with each other. [ABSTRACT FROM PUBLISHER]

In order to reduce carbon dioxide and air pollution emissions, fuel cell vehicles (FCVs) are being developed, and CFRP pressure vessels have been used as the hydrogen storage systems for the FCVs. Since the FCVs are expected to increase driving distances of at least over 500 km, which is similar to those of conventional gasoline-fueled vehicles, the storage pressure of hydrogen must be raised from 35 to 70 MPa. It is important to decrease the amount of carbon fibers in order to reduce the cost and weight of the CFRP pressure vessels. In this study, a fast fabrication method for the cylindrical-shaped grids (CSG) composed of hoop stiffeners and helical stiffeners was developed with a particular mandrel and a 3-axis filament winding apparatus. Then, the CFRP pressure vessel was inserted into the CSG, and burst tests of the CFRP pressure vessels reinforced with and without the CSG were conducted. Moreover, their experimental results were compared with numerical ones obtained by a FEM analysis, and the mechanical properties and the reinforcement effects of the CFRP pressure vessels reinforced with the CSG were investigated. [ABSTRACT FROM AUTHOR]

Thermoplastic resin used as a matrix of fiber reinforced thermoplastics (FRTPs) is composed of high polymers that remain highly viscous even at a higher temperature than their melting points. As a result, they need a higher temperature, a higher pressure and longer process time to allow them to bond with fibers and consequently require large and specialized facilities. In this paper, a simple and fast fabrication method of vacuum assisted resin transfer molding (VARTM) method for hybrid fiber reinforced thermoplastic (HFRTP) was introduced. In order to fabricate HFRTP with the VARTM, glass and carbon fabrics were used as reinforcement and in-situ polymerizable epsilon caprolactam (ɛ-caprolactam) was used as the matrix. The obtained HFRTP had neither voids nor unfilled parts because the liquid state of ɛ-caprolactam was very low viscosity before polymerization. The fabrication method of the HFRTP proposed here showed a faster fabrication one compared with conventional fabrication methods. In order to apply this HFRTP to automotive structures, the performances of the HFRTP showed not only superior mechanical properties but also suitable for high-speed molding without expensive facilities, namely, within a few minute process time with a vacuum pump because they could be released from the mold without a cooling process. [ABSTRACT FROM AUTHOR]

Since isogrid structures are composed of triangular grid stiffeners and a surface skin, they have a high specific strength and stiffness. These structures are now being mainly used for aerospace applications. In order to produce a metal isogrid cylindrical shell, most of the thick metal plates must be cut off while the remaining thin surface skins with the stiffeners and both ends of the skins are welded to each other. This process needs a long lead time and a high cost, and unstable behaviors are observed in the joint parts. On the other hand, carbon fiber reinforced plastics (CFRP) isogrid cylindrical shells can be fabricated with an integral method by using a filament winding apparatus. In this study, a fabrication method of the CFRP isogrid cylindrical shells is proposed and their compressive tests are carried out to investigate the reinforcement effect of the grids on the CFRP isogrid cylindrical shells. Furthermore, the results of the static compressive tests are compared with numerical ones obtained by finite element method (FEM). [ABSTRACT FROM AUTHOR]

This paper describes how to generate nanofibers from four kinds of polymers, such as polylacticacid, polyamide 6, polyethersulfone, and triacetylcellulose by using an electro spinning method. They are used as surface treatments in the green composites composed of kenaf fibers as the reinforcement and biomass-UP as the matrix, respectively. In order to confirm the effects of the nanofibers, the comparisons of tensile tests are performed. The tensile strengths of specimens with the four kinds of nanofibers were from 23% to 36% higher than those of specimens without the nanofibers. Furthermore, the failure strains of two specimens with the PES and TAC nanofibers increased by 5% and 10% compared with the values without the nanofibers. [ABSTRACT FROM AUTHOR]