This work presents the experimental and finite element (FE) simulations to investigate the behavior of both unstiffened and anisogrid composite cylindrical shells subjected to low‐velocity axial impact. Impact damage has been an epidemic problem for composite structures. Even subjected to a low‐velocity impact, thin‐walled composite structures may sacrifice its load‐carrying capacity considerably due to various modes of failure. A low cost, reliable and innovative manufacturing process is proposed for the production of anisogrid cylindrical lattice structures. Initially, test coupons are fabricated as per American Society for Testing of Materials (ASTM) standards and inspected using infrared (IR) thermography to find the imperfections incurred during fabrication. The test coupons without defects were only taken into account for material characterization. FE simulations were carried out on both the unstiffened and anisogrid shells using LS‐DYNA® for a series of low‐velocity impacts. Also these shell structures were subjected to impact loading experimentally for the validation of the numerical results. The results of these studies indicate that the anisogrid model presented in this work possesses a great load‐carrying capacity than an unstiffened shell under dynamic loading conditions, also the weight of the structure has been reduced up to 51.27%. Numerical simulation results are in good agreement with the experimental data, having less than 11.56% of maximum deviation on the energy absorption value.
Lattice structures have been widely used in aircraft and automobile industries due to their excellent mechanical properties namely high specific strength, specific stiffness, and energy absorption capability. On the other hand, additive manufacturing that is considered as an essential for Industry 4.0 offers incredible opportunities for product development and production flexibility. Previous research on 3D printed isogrid structures focused on isogrid panels and their buckling behavior, whereas isogrid lattice cylindrical shells garnered less attention. This work reports the effect of short carbon fiber reinforcement with polyamide three‐dimensional printing material on the compression response of isogrid lattice shell structures by experimental and numerical modeling. Isogrid cylindrical shells were three dimensionally printed using fused deposition modeling. Initially, test coupons were printed using polyamide and carbon fiber reinforced polyamide and their mechanical properties were found using uniaxial tensile testing. The obtained tensile properties were given as an input to the numerical modeling performed using LS‐DYNA®. The peak load and the maximum displacement of the printed isogrid lattice shells subjected to axial compression loads were experimentally evaluated. The numerical findings were compared with those produced using experimental methods. The error in estimating the peak load of lattice cylinders through numerical modeling was limited to 5.35%. The effect of geometric parameters namely rib width (helical and hoop), shell thickness, helical angle of ribs on the buckling strength was also studied.
This work presents the experimental and finite element simulations to investigate the behavior of both unstiffened and anisogrid composite lattice cylindrical shells under low velocity axial impact. Impact damage has been an epidemic problem for composite structures. Even subjected to a low velocity impact, composite may sacrifice its load carrying capacity considerably due to various modes of failure. The test coupons fabricated as per American Society for Testing of Materials (ASTM) standards were put through Infrared (IR) thermography to find the imperfections during fabrication. The test coupons without defects were only taken into account for material characterization. Finite Element simulations are carried out on both the unstiffened and anisogrid shell structures using LS-DYNA® for a series of low velocity impacts. Also these shell structures were subjected to impact load experimentally for the validation of the results. The results of these studies indicate that the anisogrid model presented in this work possess greater load carrying capacity than unstiffened shell under dynamic loading conditions, also the weight of the structure has been drastically reduced.
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