Please clear handwriting if you write by hand SECTION A dens

SECTION A density for EIGHT of Figure 1 the between streness and the main classes of engineering Ceramics 1.000 Co posies Wood and wood product 2 Ace 10 Metals Ceramics and alloys ste Polymers Rubbers 1,000 3,000 10.000 30.000 300 100 DENSITY (kg/m Heavy Figure 1 Graph showing the relationship between stiffness and density for a range of classes of engineering materials In the context of the information in Figure 1: (i) EXPLAIN why wood is a versatile material with many applications. [4 marks] (ii) COMPARE the properties of steel, aluminium alloys and carbon fibre reinforced plastic (CFRP) (a composite), showing approximately where the three materials lie on the graph. [6 marks] (iii) DESCRIBE factors in material selection that are not captured in Figure 1. [6 marks]

Solution

1. Wood is a light material and its density ranges from 100 to 1500 kg/m³. Wood is placed at the left of the graph in the \"Light\" range. Its stiffness or Young\'s modulus ranges from 0.1 to 30 Gpa, a wide range which makes it suitable for a variety of applications. For some categories of wood the Young\'s modulus is same as that for a few metals. As wood is light as well as structurally strong and available in a variety of strenght to weight ratios it is a widely used engineering material.

2. Young\'s modulus (GPa) Density Kg/m³

Steel 200 7800

Aluminium 70 2700

Carbon fibre reinforced plastic 150 1600

3. Factors include tensile strength, hardness, ductility, toughness, fatigue strength, creep, thermal coductivity, resistance to corrosion etc .