Studies on the testing methods for interfacial fracture toughness for evaluating the interfacial property of dental prostheses.

通过改变试件的厚度、宽度、长度和初始裂纹长度，研究了不透明瓷/金属和粘接树脂/金属界面两种不同材料之间的界面断裂韧性(I、II型)的测试方法。试件为夹层结构，有初始裂纹。在I类试验中，试件用两个正方形截面块加载，在试件端部粘贴一个用于加载的孔。并结合边缘载荷和裂纹张开位移的测量，用移动显微镜测量了裂纹长度。采用三点弯曲试验进行II型试验。根据他们的测量结果，得到了界面断裂韧度的两个值。取得的结果如下。不透明瓷/金属试件的厚度为0.3~0.5 mm，宽度为3~5 mm，长度以30~40 mm为宜。初始裂纹长度在8~10 mm范围内较为合理。测试速度为0.05 mm/min。作为参考数据，该试件的界面断裂韧性约为15J/m~2。其次，对于树脂/金属粘接试件，其厚度在1.5~2.0 mm范围内是合理的，因为断裂韧性值在400~500J/m~2之间。考虑到粘接过程，5 mm的宽度比10 mm的宽度要好。长度仅为50 mm。顺便说一句，粘合树脂层的厚度约为70um。初始裂纹长度以15-20 mm为宜，因为扩展后的裂纹长度相对容易测量。因此，为了评价界面性质，人们认识到这种断裂韧性测试方法更有效。

Testing method for interfacial fracture toughness (modes I and II) between two different materials in a dental prosthesis, such as opaque porcelain/metal and adhesive resin/metal interfaces, was investigated by changing thickness, width, length and intial crack length of test specimen. Test specimen is of sandwich construction with an intial crack. In mode I testing, the test speciman was loaded by using two square cross-sectional block with a hole for loading bonded on test specimen end. And the crack length was measured by using a traveling microscope in conjunction with the measurement of the marginal load and crack opening displacement. Mode II testing was done by 3-point bending test. From their results of measurement, both values of interfacial fracture toughness was obtained. Results obtained are as follows. In case of the opaque porcelain/metal test specimen, its thickness of 0.3-0.5mm and its width of 3-5mm were appliciated, and its length was enough in region of 30-40mm. Initial crack length in region of 8-10mm was reasonable. Testing speed of 0.05mm/min was appreciated. As reference data, interfacial fracture toughness of this test specimen was about 15j/m^2. Next, in adhesive resin/metal test specimen, its thickness in region of 1.5-2.0mm was reasonable because the values of fracture toughness were shown for 400-500j/m^2. Width of 5mm was good than that of 10mm considering the procedure of adhesion. Length was 50mm only. By the way, thickness of adhesive resin layr was about 70mum. Initial crack length of 15-20mm was good because th crack length propagated was comparatively easy to measure. Therefore, in order to evaluate the interfacial property, it was recognized that such the testing methods for fracture toughness were more effective.