Mechanical Properties Of Porous Composites Research Articles

A fractal model of effective mechanical properties of porous composites

In this work, a simple but effective fractal model is proposed to predict the mechanical properties of complex porous composites. By extending the Mori-Tanaka and Double Inclusion models, we develop a computationally efficient algorithm based on the mean-field homogenization, to quickly determine the macroscopic elastic properties of the random porous media by the fractal theory. The random pore sizes and locations are properly characterized by a single fractal dimension, and the fractal model agrees well with the numerical results obtained by the finite element homogenization technique and the existing experimental data from literature. Moreover, the effect of pore size distribution has been investigated, indicating that the elastic properties decrease with the increase in the fractal dimension. In particular, the computation time can be reduced from 4 h for the finite element analysis to 15 s based on the fractal model. Based on the mathematically analogous governing equations, the present fractal modeling has great potential to determine the other significant physical properties such as thermal conductivity and coefficient of thermal expansion.

Ultra-high mechanical properties of porous composites based on regenerated cellulose and cross-linked poly(ethylene glycol)

The ultra-high mechanical, biocompatible and biodegradable porous regenerated cellulose/poly(ethylene glycol) (RC/PEG) composites with double network structure were fabricated via an simple method to dissolve cellulose followed by UV irradiation. The porous structure of RC/PEG was sensitively altered by PEG contents, which led to the porous structure morphology transition from 3D fibrillar network to close-grained sheet-like-network with the loading of cross-linked PEG. The porous RC/PEG showed excellent mechanical properties, i.e., the compressive strength can reach 33 times higher than that of neat RC (0.07MPa) at the compressive strain of 30%. Porous RC/PEG also displayed outstanding properties with openly porous structure and structural stabilization. Besides, porous RC/PEG exhibited good water absorbency, which the water absorbency ratio at equilibrium state was 83% higher than that of porous RC. This work provides an environmentally friendly and simple pathway to prepare non-toxic and biocompatible porous regenerated cellulose-based composites with high strength, structural stabilization and good water absorbency, which could be useful for packaging, biomedical applications, sewage purification, etc.

Mechanical properties of porous β-tricalcium phosphate composites prepared by ice-templating and poly(ε-caprolactone) impregnation.

In this study ceramic scaffolds of the bioresorbable and osteoconductive bioceramic β-tricalcium phosphate (β-TCP) were impregnated with the bioresorbable and ductile polymer poly(ε-caprolactone) (PCL) to investigate the influence of the impregnation on the mechanical properties of the porous composites. The initial β-TCP scaffolds were fabricated by the ice-templating method and exhibit the typical morphology of aligned, open, and lamellar pores. This pore morphology seems to be appropriate for applications as bone replacement material. The macroporosity of the scaffolds is mostly preserved during the solution-mediated PCL impregnation as the polymer was added only in small amounts so that only the micropores of β-TCP lamellae were infiltrated and the surface of the lamellae were coated with a thin film. Composite scaffolds show a failure behavior with brittle and plastic contributions, which increase their damage tolerance, in contrast to the absolutely brittle behavior of pure β-TCP scaffolds. The energy consumption during bending and compression load was increased in the impregnated scaffolds by (a) elastic and plastic deformation of the introduced polymer, (b) drawing and formation of PCL fibrils which bridge micro- and macrocracks, and (c) friction of ceramic debris still glued together by PCL. PCL addition also increased the compressive and flexural strength of the scaffolds. An explanatory model for this strength enhancement was proposed that implicates the stiffening of cold-drawn PCL present in surface flaws and micropores.