Instrumented falling weight impact (IFWI) properties of two-dimensional (2D) weft-knitted carbon-fiber (CF)-reinforced poly(ethyl methacrylate) (PEMA) and poly(ether ether ketone) (PEEK) composites with a reinforcement content of V f ≈ 35 and 51 vol.%, respectively, were studied under low-energy and perforation impact conditions. Results indicated that the transverse impact response of these thermoplastic composites strongly depends on the ductility of the matrix, on fiber/matrix adhesion, and on the stitch (rib) structure (size, stretching of the fabrics) of the knitted fabric reinforcement. The highest thickness-related perforation impact energy was found for the knitted CF-reinforced PEEK composite (≈15 J/mm) due to its high reinforcement content, high matrix ductility, and good fiber/matrix bonding.
After myocardial infarction, the implantation of stem cell seeded scaffolds on the ischemic zone represents a promising strategy for restoration of heart function. However, mechanical integrity and functionality of tissue engineered constructs need to be determined prior to implantation. Therefore, in this study a novel pulsatile bioreactor mimicking the myocardial contraction was developed to analyze the behavior of mesenchymal stem cells derived from umbilical cord tissue (UCMSC) colonized on titanium-coated polytetrafluorethylene scaffolds to friction stress. The design of the bioreactor enables a simple handling and defined mechanical forces on three seeded scaffolds at physiological conditions. The compact system made of acrylic glass, Teflon®, silicone, and stainless steel allows the comparison of different media, cells and scaffolds. The bioreactor can be gas sterilized and actuated in a standard incubator. Macroscopic observations and pressure-measurements showed a uniformly sinusoidal pulsation, indicating that the bioreactor performed well. Preliminary experiments to determine the adherence rate and morphology of UCMSC after mechanical loadings showed an almost confluent cellular coating without damage on the cell surface. In summary, the bioreactor is an adequate tool for the mechanical stress of seeded scaffolds and offers dynamic stimuli for pre-conditioning of cardiac tissue engineered constructs in vitro.
