Pore Structure and Deformation Correlation of an Aluminum Foam Sandwich Subject to Three-Point Bending

An Al-Si matrix foam sandwich (AFS) with 6063 Al alloy cover sheets was fabricated by hot rolling combined with melt foaming. A foamable AlSiMg1/SiCp matrix precursor was prepared by the melting route. Hot rolling at 480 °C was carried out to obtain a mechanical bonding interface between the cover sheet and the foamable precursor. Meanwhile, the pore structure of the AFS was deeply affected by the foaming temperature and foaming time during the foaming process. Different pore growth mechanics of the crack-like pore disappearance mechanism (CDM) and pore active expansion mechanism (AEM) were concluded based on the pressure difference in pores inside and outside. Three bending tests were applied to three types of AFSs with different pore structures to evaluate the relation between pore structures and AFS mechanical properties. The bending property of the AFS with fewer layers of pores is like that of a dense material. The bending property of the AFS with a pore size in the range of 0~1 mm presents a typical sandwich shear failure mode. The AFS with a uniform pore structure, in which the shapes of the pores are predominately polygons and the pore diameter is concentrated in the range of 0.5~3 mm, processes a good energy absorption capacity, and the bending stress-strain curve fluctuates greatly after the first stress drop.

Process Optimization for the Continuous Production of a Gastroretentive Dosage Form Based on Melt Foaming

Several drugs have poor oral bioavailability due to low or incomplete absorption which is affected by various effects as pH, motility of GI, and enzyme activity. The gastroretentive drug delivery systems are able to deal with these problems by prolonging the gastric residence time, while increasing the therapeutic efficacy of drugs. Previously, we developed a novel technology to foam hot and molten dispersions on atmospheric pressure by a batch-type in-house apparatus. Our aim was to upgrade this technology by a new continuous lab-scale apparatus and confirm that our formulations are gastroretentive. At first, we designed and built the apparatus and continuous production was optimized using a Box-Behnken experimental design. Then, we formulated barium sulfate-loaded samples with the optimal production parameters, which was suitable for in vivo imaging analysis. In vitro study proved the low density, namely 507 mg/cm3, and the microCT record showed high porosity with 40 μm average size of bubbles in the molten suspension. The BaSO4-loaded samples showed hard structure at room temperature and during the wetting test, the complete wetting was detected after 120 min. During the in vivo study, the X-ray taken showed the retention of the formulation in the rat stomach after 2 h. We can conclude that with our device low-density floating formulations were prepared with prolonged gastric residence time. This study provides a promising platform for marketed active ingredients with low bioavailability.