4.7 Article

Understanding the effect of defects on compressive behaviors of closed-cell foams: Experiment and statistical model

Journal

COMPOSITES PART B-ENGINEERING
Volume 244, Issue -, Pages -

Publisher

ELSEVIER SCI LTD
DOI: 10.1016/j.compositesb.2022.110179

Keywords

Foam; Defect; Compressive behavior; Statistical model; Additive manufacturing

Funding

  1. National Natural Science Foundation of China [12102390, 12002111, 11972310]
  2. Higher Education Discipline Innovation Project [BP0719007]
  3. China Postdoctoral Science Foundation [2021M692788, 2022T150568]

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This study experimentally investigates the effect of defects on foam materials and proposes a statistical model that considers the influence of defects. The results show that the defect of missing cell-wall greatly affects the compressive behaviors of foams, while the defect of missing cell-core has a negligible influence on mechanical properties.
Although defects cannot be avoided in foam materials, they are barely considered in existing models where relative density plays a dominating role. Despite sharing the same relative density, foams with and without defects may exhibit different mechanical properties. To study the effect of defects, this paper experimentally investigates the closed-cell foams with different levels of defects, and proposes a statistical model considering the influence of defect. The polylactic-acid Voronoi foams with deliberately induced defects, including missing cellcore (30% and 50%) and missing cell-wall (0%-50%), are firstly produced using the additive manufacturing technique. After that, a number of quasi-static experiments are conducted. Results indicate that the defect of the missing cell-core insignificantly affects the mechanical properties, while, the defect of the missing cell-wall greatly affects the compressive behaviors of foams. In particular, specimens with the defect of a missing cell-core correspond to intact foams with a larger cell-size, and only cell-wall buckling is observed. For foams with the defect of a missing cell-wall, a new deformation mechanism named cell-wall vacancy occupation is defined and reported. This mechanism makes specimens exhibit a lower stress level and a more obvious strain hardening behavior. Based on the experimental data, a statistical model is established. This model offers both forward prediction and inverse calculation of the effect of defect on the compressive behaviors of foams with good accuracy.

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