A Voronoi-diagram analysis of the microstructures in bulk-molding compounds and its correlation with the mechanical properties

Investigation on crashworthiness and mechanism of a bionic antler-like gradient thin-walled structure

Inspired by an impact-resistant antler, a novel size-gradient thin-walled structure is designed as an energy absorber. Its crashworthiness and mechanism are investigated by finite element simulation. The results show that the bionic-antler gradient structure has excellent crashworthiness performance with the specific energy absorption (SEA) of 2.17 and 1.29 times that of cylinder and fractal spider web, respectively, and the crushing force efficiency as high as 91.54%. Furthermore, when its SEA is the same as that of the fractal spider web, the peak crushing force can be reduced by 35%. The bionic-antler gradient structure produces many folds due to small folding wavelength, which expands the scope of energy storage area and improves the value of energy storage. Increasing properly the cell size-gradient or decreasing the average cell size can further enhance the crashworthiness performance of the bionic-antler gradient structure.

Absorbable mineral nanocomposite for biomedical applications: Influence of homogenous fiber dispersity on mechanical properties

Electrospun micro- and nanosized fibers are frequently used as reinforcing elements in low temperature ceramic composites for biomedical applications. Electrospinning of fibers yield, however, not individual fibers, but rather fiber-mats that are difficult to separate. Most investigations have been performed on diced mats and highly nonhomogenous composites. We examined the influence of dispersed electrospun single micro- and nanometer fibers on the mechanical properties of calcium phosphate cement composites. Absorbable poly-l-lactic-acid was electrospun yielding fibers with diameters of 244 ± 78 nm, named nanofibers (NF), and 1.0 ± 0.3 μm, named microfibers (MF). These fibers were cut using a particle assisted ultrasonication process and dispersed with hydroxyapatite nanoparticles and composites of low (5%) and high (30%) NF/MF content were engineered. The homogeneity of the fiber distribution was investigated by analyzing fracture areas regarding the number of fibers and Voronoi area size distribution. Variation of fiber distribution was significantly lower in the NF group as compared to the MF group. For composites containing 5% NF (V/V), an eightfold increase in the compressive fracture strength, and for the 30% NF (V/V) a threefold increase compared was measured. The composite containing 5% NF was identified as optimal regarding fiber distribution and strength. Our new method of engineering these composites allows for high volume fractions of NF with low variation in fiber distribution to be incorporated into composites, and shows the importance of using single filaments as reinforcing agents. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 850-857, 2018.