Experimental Research and Numerical Analysis of the Elastic Properties of Paper Cell Cores before and after Impregnation

Abstract

The research hypothesis states that the impregnation of the honeycomb paper core of lightweight sandwich panels with modified starch, sodium silicate and epoxy resin (LiquidWood®) resin has a significant effect on its elastic properties. In this study, a recycled paper was used in three thicknesses, seven types of cell shapes, including two after numerical optimization and three types of impregnating agents. The method of digital image analysis determined the elastic constants of manufactured paper cores, which were subjected to axial compression in two directions. Based on the experimental results, elastic constants of the cores were calculated and compared with the results of numerical calculations. It has been shown that each of the impregnating solutions used improved the stiffness of the paper core. The best results were obtained for LiquidWood® epoxy resin and modified starch. An important parameter of cell geometry affecting their rigidity is the angle of the cell wall φ, as well as the arrangement of the common cell wall in relation to the direction of load. The numerical models developed were positively verified.

Influence of Impregnation with Modified Starch of a Paper Core on Bending of Wood-Based Honeycomb Panels in Changing Climatic Conditions

“…A series of scientific publications [ 66 , 67 , 68 ] describes in detail the method of selecting cell geometry and its production processes. On this basis, keeping the previously used determinations, cores with cells geometry C, E, F were selected for the tests ( Figure 1 ).…”

“…C and E cores are made of the most used paper in the furniture industry [ 66 , 69 ]. The decision to use cores based on C, E, F cells to create light furniture panels results from a thorough analysis of the elastic constants of individual cores carried out in the publication of Słonina et al [ 68 ]. The exact dimensions of individual types of cells and their relative density are presented in Table 1 .…”

“…Depending on their thickness and impregnation, these papers were marked with the symbols 15N, 25N, 15S, 25S, respectively. The paper [ 68 ] presents in detail the method of paper impregnation, forming cells, and obtaining cores. In addition, the results illustrating the elastic properties of paper, which were determined following the PN-EN ISO 1924-2 standard [ 70 ], are also presented.…”

“…The first group of beams was stored in dry conditions (D), i.e., in the climate of the production hall at the temperature T = 25 °C and relative air humidity H = 45%, while the second group of beams was stored in a climate similar to tropical (W), i.e., at the temperature T = 28 °C and relative air humidity of H = 85%, until the mass of the samples stabilizes. The selected air temperature and relative humidity complied with EN 318 (2002) requirements and were used as variable factors in the works [ 68 , 75 , 76 ].…”

Properties of Plywood Made from Perforated Veneers

“…Wood materials with a weight of less than 500 kg•m −3 are defined as lightweight panels, less than 350 kg•m −3 very lightweight panels, and less than 200 kg•m −3 ultra lightweight panels. Properties of lightweight wood-based materials have been researched by several authors [11][12][13][14][15][16][17][18][19]. One of the lightweight wood materials (plywood type), with patented production technology, won several awards in 2019 and 2020 [20].…”