Yoshihara Hiroshi, Yoshinobu Masahiro, Maruta Makoto
Faculty of Science and Engineering, Shimane University, Matsue 690-8504, Japan.
Faculty of Science and Technology, Shizuoka Institute of Science and Technology, Fukuroi 437-8555, Japan.
Polymers (Basel). 2024 Jun 28;16(13):1857. doi: 10.3390/polym16131857.
Extruded polystyrene (XPS) is frequently used in the construction of many different structures. Therefore, it is necessary to appropriately characterize its mechanical properties to ensure the safety of said structures. Among the available characterization tests, static bending tests are simple and easy to perform; owing to these characteristics, they should be performed more frequently than other tests. In static bending tests on XPS, there are several challenges owing to the high flexibility of XPS, and the chosen testing method and sample configuration affect the accuracy of characterization. For cellular plastics, including XPS, three-point bending (TPB) test methods are standardized by the International Organization for Standardization (ISO) and Japanese Industrial Standards (JIS) as in ISO 1209-2:2007 and JIS K 7221-2:2006, respectively, where the sample configurations are determined. Therefore, TPB tests of cellular plastics have been conventionally performed based on these standardized methods to characterize the bending properties. In contrast, investigations on the effects of testing methods and sample configurations have often been neglected due to the existence of these standardized methods. However, to characterize the bending properties of XPS accurately, the effects of the testing method and sample configuration must be examined in detail. In this study, three bending properties (Young's modulus, proportional limit stress, and bending strength) of samples cut from an XPS panel were determined using three-point bending (TPB), four-point bending (FPB), and compression bending (CB) tests with varying sample span/depth ratios from 5 to 50 at intervals of 5, and statistical analyses were performed to determine the relevance of the tests. The effect of sample configuration on Young's modulus could be reduced when the span/depth ratio range was 25-50, 25-50, and 15-50 in the TPB, FPB, and CB tests, respectively, whereas that on the proportional limit stress was reduced in the span/depth ratio range of 5-50, 20-50, and 15-50 in the TPB, FPB, and CB tests, respectively. Additionally, the effect on the bending strength was reduced when the span/depth ratio range was 5-50, 20-50, and 5-50 in the TPB, FPB, and CB tests, respectively. Therefore, these results suggest that the TPB and CB tests were more feasible than the FPB test when the span/depth ratio was determined as being 25-50 and 15-50, respectively. However, clear differences were observed in the sample bending properties determined in these tests. In light of these findings, further studies should be conducted to elucidate these differences.
挤塑聚苯乙烯（XPS）常用于多种不同结构的建造。因此，有必要对其力学性能进行适当表征，以确保这些结构的安全性。在现有的表征测试中，静态弯曲测试简单易行；由于这些特点，它们应比其他测试更频繁地进行。在对XPS进行静态弯曲测试时，由于XPS的高柔韧性存在几个挑战，并且所选的测试方法和样品配置会影响表征的准确性。对于包括XPS在内的泡沫塑料，国际标准化组织（ISO）和日本工业标准（JIS）分别在ISO 1209-2:2007和JIS K 7221-2:2006中对三点弯曲（TPB）测试方法进行了标准化，其中确定了样品配置。因此，传统上一直基于这些标准化方法对泡沫塑料进行TPB测试，以表征其弯曲性能。相比之下，由于存在这些标准化方法，对测试方法和样品配置影响的研究常常被忽视。然而，为了准确地表征XPS的弯曲性能，必须详细研究测试方法和样品配置的影响。在本研究中，使用三点弯曲（TPB）、四点弯曲（FPB）和压缩弯曲（CB）测试，以5为间隔，从5到50改变样品跨度/深度比，测定了从XPS板切割的样品的三种弯曲性能（杨氏模量、比例极限应力和弯曲强度），并进行了统计分析以确定测试的相关性。在TPB、FPB和CB测试中，当跨度/深度比范围分别为25-50、25-50和15-50时，样品配置对杨氏模量的影响可以降低，而在TPB、FPB和CB测试中，当跨度/深度比范围分别为5-50、20-50和15-50时，对比例极限应力的影响降低。此外，在TPB、FPB和CB测试中，当跨度/深度比范围分别为5-50、20-50和5-50时，对弯曲强度的影响降低。因此，这些结果表明，当跨度/深度比分别确定为25-50和15-50时，TPB和CB测试比FPB测试更可行。然而，在这些测试中确定的样品弯曲性能存在明显差异。鉴于这些发现，应进一步开展研究以阐明这些差异。
