El-Sagheer Islam, Abd-Elhady Amr A, Sallam Hossam El-Din M, Naga Soheir A R
Mechanical Design Department, Faculty of Engineering, Helwan University, Cairo 11718, Egypt.
Materials Engineering Department, Zagazig University, Zagazig 44519, Egypt.
Polymers (Basel). 2021 Sep 16;13(18):3129. doi: 10.3390/polym13183129.
The main objective of this work is to predict the exact value of the fracture toughness () of fiber-reinforced polymer (FRP). The drawback of the American Society for Testing Materials (ASTM) E1922 specimen is the lack of intact fibers behind the crack-tip as in the real case, i.e., through-thickness cracked (TTC) specimen. The novelty of this research is to overcome this deficiency by suggesting unprecedented cracked specimens, i.e., matrix cracked (MC) specimens. This MC exists in the matrix (epoxy) without cutting the glass fibers behind the crack-tip in the unidirectional laminated composite. Two different cracked specimen geometries according to ASTM E1922 and ASTM D3039 were tested. 3-D FEA was adopted to predict the damage failure and geometry correction factor of cracked specimens. The results of the TTC ASTM E1922 specimen showed that the crack initiated perpendicular to the fiber direction up to 1 mm. Failure then occurred due to crack propagation parallel to the fiber direction, i.e., notch insensitivity. As expected, the of the MC ASTM D3039 specimen is higher than that of the TTC ASTM D3039 specimen. The of the MC specimen with two layers is about 1.3 times that of the MC specimen with one layer.
这项工作的主要目标是预测纤维增强聚合物（FRP）的断裂韧性（）的确切值。美国材料与试验协会（ASTM）E1922试样的缺点是，与实际情况一样，裂纹尖端后面缺乏完整的纤维，即全厚度裂纹（TTC）试样。本研究的新颖之处在于，通过提出前所未有的裂纹试样，即基体裂纹（MC）试样，来克服这一缺陷。这种MC存在于基体（环氧树脂）中，而在单向层合复合材料中，裂纹尖端后面的玻璃纤维未被切断。根据ASTM E1922和ASTM D3039测试了两种不同的裂纹试样几何形状。采用三维有限元分析（3-D FEA）来预测裂纹试样的损伤失效和几何修正因子。TTC ASTM E1922试样的结果表明，裂纹在垂直于纤维方向上起始至1毫米。随后由于裂纹沿纤维方向扩展而发生失效，即缺口不敏感。正如预期的那样，MC ASTM D3039试样的 高于TTC ASTM D3039试样。两层MC试样的 约为一层MC试样的1.3倍。
