Question A.2 (a) With the aid of diagram, discuss the structure and property difference between open cell foam and closed cell foams with reference to typical applications. [4 marks] (b) Briefly explain what a gas foaming process. [4 marks] (c) Sketch and discuss the stress-strain relationship of a cellular solid (e.g. Honeycomb structures) loaded in compression, point out the three deformation regimes on the curve, and briefly explain how the energy absorbed can be calculated.