Text Box: Selection and Focus

 

Because of the number of options in the composites world, the field of options had to be narrowed to bring this project into focus. After research and help from expert advisors, decisions were made based on the feasibility of each portion of the project.  In this case, a design matrix was not used because the nature of the project provided enough constraints to vastly narrow the field. The areas of research were materials, resin, molding, and curing.  

 

Material

 

Because of weight restrictions, the main fuselage shell will have to be constructed from carbon fiber.  Glass fiber and Kevlar are very strong, but in order to keep the fuselage within 130% of the weight of the current model, the shell must be made predominantly from light carbon fiber.

 

Resin

 

The first structures will be constructed with Epon epoxy because of strength and availability.  According to resources, this is one of the main industry standards for use with carbon fiber.  If weight reduction is required, less dense epoxy from Epon can be used.

 

Molding

 

To increase aerodynamics and shell integrity, the group will explore the possibility of creating a female mold.  The current fuselage is constructed from a male mold where the material is wrapped around the mold.  This makes the inside of the shell very smooth and precise and leaves the outside very susceptible to imperfections that can cause drag.  A female mold would lay the carbon fiber into a mold with the outside of the shell being formed by the mold. This increases aerodynamics and efficiency. 

 

 

 

 

 

Curing

 

The shell will be cured at room temperature because of the availability of an autoclave.  With proper catalysts, this process creates a strong part that allows for mass production without the requirement of a large autoclave.  

 

Focus

 

The new, narrowed focus will deal with the construction of more accurate and efficient female molds.  The team will examine the feasibility of making a mold that can produce multiple shells at one time.  Along with molding, the team will investigate the most efficient ways to reinforce the carbon fiber shell with composite foam, Kevlar and other materials.  This will increase the MAV’s ability to absorb energy on landing or impact without structural failure.   A new area of focus is fastening the two molded halves of the fuselage together.  Currently, the fuselage is assembled with polymer screws so that, on impact, the screws shear instead of cracking the shell.  The group will investigate other methods of joining these halves to more efficiently spread stress concentration and reduce weight.