6 research outputs found
Entwicklung einer Messzelle zur Bestimmung von Kompaktierungs- und Permeabilitätskennwerten bei flächigen Faserhalbzeugen
The popularity of composite materials is constantly growing, which can be verified by
the rising number of composite parts in our everyday life. Examples of composite
parts can be found in the Airbus A 380 or the constantly increasing number of wind
turbines which contain composite rotor blades of over 50m length. Because of the
main features of composites, which are light weight combined with high strength and
the possibility of tailoring the strength and the stiffness of the composite according to
the requirements, their application is highly efficient and economic.
In order to manufacture a composite part by employing a Liquid Composite Molding
Process (LCM), it is first necessary to select an appropriate manufacturing process
such as the Resin Transfer Molding Process (RTM) and to design a mold which corresponds
to the requirements of the selected process. Then the stacking sequence of
the individual fibrous reinforcements is designed to withstand the loads on the final
part. To achieve an efficient composite manufacturing process, pre-shaped, handable,
dry reinforcing structures, so called preforms, need to be applied. Such preforms
can be assembled either by using conventional binder technologies or by the
recently developed “cut and sew approach”. A variety of available software simulation
tools support the design engineer in this task. These tools are, on the one hand, a
fast way of gaining information about the expected loads the mold has to endure during
the injection process. On the other hand, they provide the possibility to optimize
the injection process and its process parameters and to identify critical points of incomplete
saturation. With this information at hand, the design of the mold can be adjusted
in order to obtain optimal processing conditions for a slim and efficient production
cycle.
A prerequisite for employing these powerful simulation tools is to obtain thorough
knowledge of the required input parameters concerning the fibrous reinforcement to
be used. The most important input parameters are the compaction behavior and the
permeability of the fibrous stacking sequence. Because of the absence of modelbased
tools to provide this input information experimental determination methods
have to be employed.
This work introduces two semi-automated measurement cells which determine the inplane
permeability of fibrous reinforcements in an efficient manner, i.e. the dielectrical permeability work cell and the optical compaction and permeability work cell. The
latter of which can determine both the required compaction and the permeability information
in one single experiment. The design and manner of operating of the optical
compaction and permeability work cell is described and its functionality is validated
by a comparison of experimental results
Entwicklung einer Messzelle zur Bestimmung von Kompaktierungs- und Permeabilitätskennwerten bei flächigen Faserhalbzeugen
The popularity of composite materials is constantly growing, which can be verified by
the rising number of composite parts in our everyday life. Examples of composite
parts can be found in the Airbus A 380 or the constantly increasing number of wind
turbines which contain composite rotor blades of over 50m length. Because of the
main features of composites, which are light weight combined with high strength and
the possibility of tailoring the strength and the stiffness of the composite according to
the requirements, their application is highly efficient and economic.
In order to manufacture a composite part by employing a Liquid Composite Molding
Process (LCM), it is first necessary to select an appropriate manufacturing process
such as the Resin Transfer Molding Process (RTM) and to design a mold which corresponds
to the requirements of the selected process. Then the stacking sequence of
the individual fibrous reinforcements is designed to withstand the loads on the final
part. To achieve an efficient composite manufacturing process, pre-shaped, handable,
dry reinforcing structures, so called preforms, need to be applied. Such preforms
can be assembled either by using conventional binder technologies or by the
recently developed “cut and sew approach”. A variety of available software simulation
tools support the design engineer in this task. These tools are, on the one hand, a
fast way of gaining information about the expected loads the mold has to endure during
the injection process. On the other hand, they provide the possibility to optimize
the injection process and its process parameters and to identify critical points of incomplete
saturation. With this information at hand, the design of the mold can be adjusted
in order to obtain optimal processing conditions for a slim and efficient production
cycle.
A prerequisite for employing these powerful simulation tools is to obtain thorough
knowledge of the required input parameters concerning the fibrous reinforcement to
be used. The most important input parameters are the compaction behavior and the
permeability of the fibrous stacking sequence. Because of the absence of modelbased
tools to provide this input information experimental determination methods
have to be employed.
This work introduces two semi-automated measurement cells which determine the inplane
permeability of fibrous reinforcements in an efficient manner, i.e. the dielectrical permeability work cell and the optical compaction and permeability work cell. The
latter of which can determine both the required compaction and the permeability information
in one single experiment. The design and manner of operating of the optical
compaction and permeability work cell is described and its functionality is validated
by a comparison of experimental results
Prospective Isolation of Poised iPSC Intermediates Reveals Principles of Cellular Reprogramming
Regulation of transcriptional elongation in pluripotency and cell differentiation by the PHD-finger protein Phf5a
Pluripotent embryonic stem cells (ESCs) self-renew or differentiate into all tissues of the developing embryo and cell-specification factors are necessary to balance gene expression. Here we delineate the function of the PHD-finger protein 5a (Phf5a) in ESC self-renewal and ascribe its role in regulating pluripotency, cellular reprogramming, and myoblast specification. We demonstrate that Phf5a is essential for maintaining pluripotency, since depleted ESCs exhibit hallmarks of differentiation. Mechanistically, we attribute Phf5a function to the stabilization of the Paf1 transcriptional complex and control of RNA polymerase II elongation on pluripotency loci. Apart from an ESC-specific factor, we demonstrate that Phf5a controls differentiation of adult myoblasts. Our findings suggest a potent mode of regulation by the Phf5a in stem cells, which directs their transcriptional program ultimately regulating maintenance of pluripotency and cellular reprogramming