Department of Biomaterials Science, Institute of Dentistry, University of Turku, Turku, Finland.
J Mater Sci Mater Med. 2012 Feb;23(2):325-8. doi: 10.1007/s10856-011-4480-7. Epub 2011 Nov 10.
The aim of this study was to determine the effect of different span lengths of flexural testing on some properties of test specimens made of experimental short fiber reinforced composite resin (FC). Bar shaped specimens with different lengths were made from experimental FC composite with an average fiber length of 3 mm and particulate filler composite (PFC, control: Z250). The specimens (n = 8) were polymerized with a hand light-curing unit for 40 s and dry stored in a room temperature for 24 h before testing. Three-point flexural test for determination of ultimate flexural strength, toughness and flexural modulus of specimens was made with different span lengths (20, 15, 10, 7, 6, 5 mm) with a speed of 1.0 mm/min until fracture. By shortening the span length for specimens made of FC or PFC, the flexural modulus decreased (from ca. 11 to 4 GPa) and flexural toughness increased (from ca. 0.25 to 2.25 MPa). Reduction in flexural strength by shortening the span length was found with PFC (from 170 to 125 MPa) but not with FC, which showed reduction by span lengths from 20 to 7 mm and considerable increase of flexural strength by further shortening the span length from 7 to 5 mm. Shortening of span length of flexural testing showed linear reduction of the measured and calculated flexural properties of PFC and some properties of FC, but flexural strength values for FC were non-linearly related to the span length: the highest values were obtained with the longest and the shortest span lengths. In reporting the flexural values of composites, the span length-specimen dimension ratio, and the length of the reinforcement need to be taken into consideration.
本研究旨在确定不同弯曲测试跨度对实验性短纤维增强复合树脂（FC）制成的试件某些性能的影响。用平均纤维长度为 3mm 的实验性 FC 复合材料和颗粒状填料复合材料（对照：Z250）制成不同长度的棒状试件。用手动光固化器对试件（n=8）进行聚合，聚合 40s 后在室温下干燥储存 24h 后进行测试。用不同跨度（20、15、10、7、6、5mm）的三点弯曲试验来测定试件的极限抗弯强度、韧性和抗弯模量，跨度以 1.0mm/min 的速度缩短，直至断裂。通过缩短 FC 或 PFC 试件的跨度长度，抗弯模量降低（约 11-4GPa），抗弯韧性增加（约 0.25-2.25MPa）。缩短跨度长度会降低 PFC 的抗弯强度（从约 170MPa 降至 125MPa），但对 FC 没有影响，FC 的抗弯强度随着跨度从 20mm 缩短至 7mm 而降低，从 7mm 缩短至 5mm 时抗弯强度会显著增加。缩短弯曲测试的跨度会导致 PFC 的测量和计算弯曲性能以及 FC 的一些性能呈线性降低，但 FC 的抗弯强度值与跨度长度呈非线性关系：最长和最短跨度的抗弯强度值最高。在报告复合材料的弯曲值时，需要考虑跨度长度-试件尺寸比和增强材料的长度。
