Material Selection Requirements

• The load bearing ability of a part depends both on its design and the material from which it is made. The two must work hand in hand.
  
  
• Whenever possible, use design features/geometry to help stiffen the part. For example; a surface with a "crown" will deflect far less than a flat surface.
  

• Plastics vary greatly in physical properties. Some have lower stiffness and higher elongation at break. Others contain reinforcing fillers such as mica or glass fibers, for greater stiffness and higher load carrying capability.
  

• Select a material with adequate stiffness to keep the deflection under load within desired limits, and the stress within the limits of the material.
  
  
• Molded parts rarely exhibit properties equal to the published data for the raw material. Therefore, it is necessary to provide an adequate factor of safety in the product design so that the elastic limit of the material is not exceeded.
  
  
• Factor of safety is material and application dependant.
  
  
• Bayer MaterialScience provides static stress/strain curves for its materials, including published data for elastic limits.