{'fraction_non_alphanumeric': 0.015271838729383017, 'fraction_numerical': 0.0012217470983506415, 'mean_word_length': 5.552, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Improving the buckling strength of honeycomb cores using periodic imperfections

Composite sandwich structures are renowned for their ability to provide high flexural stiffness to weight ratios. This ability made them appealing to aerospace, wind turbines, and marine industries. The functionality of sandwich structures primarily depends on the stiffness and strength of the two composite sheets bounding their inner cores. However, when sandwich structures are subjected to transverse impacts or transverse concentrated loads, their cores can fail due to local buckling. This can subsequently trigger the failure of the entire sandwich structure. To prevent such failure, inner cores with increased buckling strengths are sought. However, currently, increasing the buckling strength of sandwich structures' cores mostly comes at the cost of increasing their weights. Conversely, this work aims to increase the buckling strength of one of the most common sandwich structure cores, namely the hexagonal honeycomb core, without increasing its weight. This is accomplished through superposing periodic imperfections to its cell walls. The introduced imperfections follow a sinusoidal form and are applied to each cell wall as a perturbation. Finite element simulations are used to determine the effect of applying the imperfections to the cell walls and to determine the imperfection level that leads to significant improvement in the core's buckling strength. Results demonstrate that the buckling strength of honeycomb cores can be enhanced by more than 30% with the introduction of a minimal amount of sinusoidal periodic imperfections.