On the Issue of Determining the Engine Power of Tensioners When Winding Products Made of «Wet» Composite Material

Products made by the method of «wet» winding from composite material are widely used in various indus-tries. The quality of future products is largely determined by the tension with which the «wet» tape is placed on the product. Until now, the electric motor of the tensioning device was selected from the condition of providing the specified maximum tension value of the composite tape, without taking into account the specific features of the tensioning device used and the geometry of the wound product. However, when winding a product with a complex geometric shape, dynamic moments occur in the electric drive, which cause additional heating of the engine. The paper analyzes the tensioning devices used for winding. They are grouped into two classes: linear and angular movement of tension rollers. For the considered tensioning devices, analytical expressions are ob-tained that relate the tension during winding with the force that the Executive electric motor must provide in static and dynamic modes. A method for selecting the drive power of tensioning devices is proposed, which takes into account the features of winding composite products made of «wet» composite material. As an exam-ple, the drive of a tensioning device is calculated when winding a pressure cylinder with a diameter of 0.2 m. the Calculations are carried out taking into account the possibility of using a worm self-braking gearbox or a planetary gearbox. Graphs of the dependence of static and dynamic moments on the motor shaft are plotted. It is shown that the use of a worm gearbox requires a more powerful drive, but when using a planetary gearbox, the electric motor must be able to stand under full load. The results obtained in this work can be used in the de-sign of new winding equipment or modernization of existing ones.

The Processing Characteristics and Mechanical Properties of Semi-Prepreg RTM Composites

A novel semi-prepreg resin transfer molding (RTM) process was developed to address difficulties associated with RTM process and to improve the mechanical properties of the resulting composites. Unidirectional semi-prepregs exhibiting relatively good overlay characteristics were prepared via prepolymerization of bismaleimide resin followed by wet winding. The processing characteristics and mechanical properties of composites fabricated via semi-prepreg RTM technology were compared with those of composites produced using a normal-prepreg compression molding process. Experimental results showed that the laminates fabricated by the semi-prepreg RTM process were of better internal quality and had superior mechanical properties as compared with laminates fabricated by the normal-prepreg compression molding process.

Crushing Behavior of Composite Hexagonal Ring System

An extensive experimental investigation of inplane crushing of composite hexagonal ring system between platens has been carried out. Woven roving glass/epoxy hexagonal ring system with different angles and arrangement were employed. The rings angles are varying between 45 and 70°. The wet winding process was used to fabricate the woven E-glass fabric /epoxy specimens. Four layers of woven E-glass fabric/epoxy wrapped over wooden mandrel to get thickness of about 3 mm. The composite hexagonal tubes were then cured at room temperature (32oC) for 24 hours to provide optimum hardness and shrinkage. Repeatability of the results was ensuring by performing the experiments on three identical specimens. Typical histories of their crushing mechanism are presented. Behavior of ring as regards the initial crushing load, post crushing load, energy absorbed and mode of crushing has been presented and discussed. Results showed that the crush failure loads and energy absorption capability are greatly affected by the hexagonal ring geometry, arrangement and loading conditions. As the ring angle increases the energy absorption capacity increases. Composite hexagonal ring with 70 degree exhibited the highest energy absorption capability among tested specimens. It is also found that energy absorption capability for systems crushed in-plane X2 higher than X1.