Influence of specimen size and density variation in the foam rise direction on the compressive behavior of PVC foams

• Published in: Materials today communications 2023-06, Vol.35, p.106003, Article 106003
• Main Authors: Rahimidehgolan, F., Magliaro, J., Altenhof, W.
• Format: Article
• Language: English
• Subjects: Compressive deformation; Density; Intermittent unloading-reloading; Materials characterization; Polymeric foam; Specimen size
• ISSN: 2352-4928; 2352-4928
• DOI: 10.1016/j.mtcomm.2023.106003

Mechanical properties governing the localized deformation mechanisms, apparent elastic modulus and their correlation to specimen geometry in polymeric foams are important phenomena that are not well understood. Despite the well-studied density variation in Functionally Graded Foams (FGF), density variation in the foam rise direction of conventional foams has not received adequate attention in the current literature. The influence of specimen size and density variation on the deformation mechanisms and mechanical properties observed in the rise direction of H-series rigid PVC foams were experimentally investigated in this study by considering four distinct specimen sizes and five nominal densities. PVC foams with different nominal densities exhibited various density variation patterns, in a range of 2.6–26.3 % variation, in the foam rise direction which were found to govern the polymeric foams’ localized deformation mechanisms and the post-yield stress drop-off behavior. The plateau stress was observed as most sensitive to the foam density; specimens with higher densities exhibited up to 19 % higher plateau stress within the foam panel with a 200 kg/m3 nominal density. While specimen thickness significantly influenced the loading elastic modulus. Intermittent unloading-reloading cycle testing was conducted on thick and thin specimens to characterize the influence of specimen thickness on the apparent elastic modulus. The influence of thickness on the unloading elastic modulus was negligible, for example, reducing the specimen thickness from 25.40 mm to 6.35 mm decreased the loading and unloading elastic moduli by 39 % and 7 %, respectively, for PVC foams with a nominal density of 200 kg/m3. Therefore, the unloading elastic modulus should be utilized in future studies for more accurate cross-comparison between the mechanical properties of specimens with significantly different thicknesses. [Display omitted]