Forces and Stresses

• It is vital a designer takes forces and stress into account when designing, how something is stretched, bent, pulled and twisted will have an impact on its effectiveness, durability and quality
• Tension


  Tensile strength is the how something withstands a pulling force
• Tension


  • Suspension bridges
  • Garden hammock
• Compression


  The opposite of tension, this is how well a material can with stand a force pressing down
• Compression


  • Table legs
  • Heavy weight squashing an object
• Bending


  When a long item is pushed down in the centre it is subjected to bending
• Bending


  • Chair withstanding bending from people sitting on it
• Torsion


  Torsion twists objects
• Torsion


  • Drill
  • Propeller
• Shear


  Shear force is when an object moves in opposite directions to create a force
• Shear


  • Cutting action of scissors
  • Guillotine
• Materials


  • Can be adapted to withstand forces and stresses better
• Lamination


  Materials can be laminated with a sandwich of something else to improve its strength
• Lamination


  • Paper made water resistant with a plasticised layer
  • Fabrics laminated with layers for waterproof, breathability and warmth (Goretex)
  • Corrugated card with a zig zag of card laminated by thin card for strength
  • Plywood with layers of wood laminated together at right angles
• Bending


  The series of bends inside corrugated card makes it difficult to bend unless it's scored
• Folding


  When a material is folded it becomes harder to bend but the fold edge (crease) becomes more flexible
• Webbing


  Woven in several directions to increase its strength, used for fabrics that must have a high tensile strength like seatbelts and climbing ropes
• Interfacing


  Applying a heat set interfacing to the underside of fabrics keeps the softness of the outer fabric whilst stiffening and stabilising it from the inside, useful for light fabrics with cuffs, collars and waistbands