Metal Space Frame or Composite Frame

This is the first major system level design decision for MSXII. MSXI was our first car to be built without a metal space frame. Although in theory a composite frame can produce a more lightweight car, the added challenge is perhaps more than Midnight Sun feels comfortable taking on for MSXII. This page will evaluate the advantages and disadvantages of each option to better guide our decision.

Decision Matrix

	Metal Space Frame	Composite Frame	Hybrid
What do other teams do?	Principia Appalachian Iowa State ETS Quebec	Stanford Calgary Michigan Dunwoody Toronto Missouri Poly Montreal	Illinois State Berkeley
Manufacturability	Waterloo student shop has a welding room. We would need to purchase a MIG or TIG welder and other welding equipment (probably < $500)	Would require careful use of adhesives and precision layups to create a good chassis
Potential Sponsors	VR3 sponsored the tubes for the control arms and roll cage on MSXI. They could be a sponsor for a space frame for MSXII
Weight	Steel has a better strength to weight ratio than aluminum. Thin walled steel is difficult to weld Aluminum is also difficult to weld	If done correctly, composites can be more lightweight than a metal chassis. Rework can be costly in terms of weight, for example, the body filler used to patch MSXI was very costly in terms of weight
Strength
Feasibility of FEA	Steel trusses have been used for decades and there are is a wealth of literature explaining techniques for analyzing stresses in steel frames "FEA steel tube chassis" - 132K hits on Google Forces in each member can be calculated and tube characteristics (wall and diameter) can be selected to a specific safety factor.	Orthotropic material properties make a composite frame more difficult to model using FEA Composites undergo very little plastic deformation before failure which can lead to abrupt, catastrophic failure. "FEA composite chassis" - 110K hits on Google Would require more advanced tool packages to perform FEA effectively.	Easier to model stresses in areas of the car where greater stiffness is crucial to the car's safety and performance - since these parts will be steel.
Team knowledge	Devon took a welding course last year and has some experience with welding steel. There is also a lot of knowledge amongst other student teams at waterloo with regards to building space frames (Baja, Formula SAE, Formula Hybrid, etc.)
Repair and Rework	Easy to modify welded steel parts ("grinder and paint makes me the welder I ain't").	Difficult to rework without adding weight or compromising strength

Mechanical

Metal Space Frame or Composite Frame

Analytics

Decision Matrix

Links and Literature

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