Liu Dong, Šavija Branko, Smith Gillian E, Flewitt Peter E J, Lowe Tristan, Schlangen Erik
1School of Physics, University of Bristol, Bristol, BS8 1TL UK.
5Present Address: Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH UK.
Int J Fract. 2017;205(1):57-72. doi: 10.1007/s10704-017-0181-7. Epub 2017 Jan 12.
In this work, porosity-property relationships of quasi-brittle materials are explored through a combined experimental and numerical approach. In the experimental part, hemihyrate gypsum plaster powder ( ) and expanded spherical polystyrene beads (1.5-2.0 mm dia.) have been mixed to form a model material with controlled additions of porosity. The expanded polystyrene beads represent pores within the bulk due to their light weight and low strength compared with plaster. Varying the addition of infill allows the production of a material with different percentages of porosity: 0, 10, 20, 30 and 31 vol%. The size and location of these pores have been characterised by 3D X-ray computed tomography. Beams of the size of mm were cast and loaded under four-point bending to obtain the mechanical characteristics of each porosity level. The elastic modulus and flexural strength are found to decrease with increased porosity. Fractography studies have been undertaken to identify the role of the pores on the fracture path. Based on the known porosity, a 3D model of each microstructure has been built and the deformation and fracture was computed using a lattice-based multi-scale finite element model. This model predicted similar trends as the experimental results and was able to quantify the fractured sites. The results from this model material experimental data and the lattice model predictions are discussed with respect to the role of porosity on the deformation and fracture of quasi-brittle materials.
在这项工作中，通过实验与数值相结合的方法探究了准脆性材料的孔隙率与性能之间的关系。在实验部分，将半水石膏粉（ ）与膨胀球形聚苯乙烯珠粒（直径1.5 - 2.0毫米）混合，以形成一种具有可控孔隙率添加量的模型材料。由于膨胀聚苯乙烯珠粒与石膏相比重量轻且强度低，它们代表了材料整体中的孔隙。改变填充材料的添加量可以制备出具有不同孔隙率百分比的材料：体积分数为0%、10%、20%、30%和31%。这些孔隙的尺寸和位置已通过三维X射线计算机断层扫描进行了表征。浇铸尺寸为 毫米的梁，并在四点弯曲下加载，以获得每个孔隙率水平的力学特性。发现弹性模量和抗弯强度随孔隙率增加而降低。已开展断口分析研究以确定孔隙在断裂路径中的作用。基于已知的孔隙率，建立了每个微观结构的三维模型，并使用基于晶格的多尺度有限元模型计算变形和断裂情况。该模型预测的趋势与实验结果相似，并且能够量化断裂部位。结合孔隙率对准脆性材料变形和断裂的作用，对该模型材料实验数据和晶格模型预测结果进行了讨论。
