4. A composite material is fixed and loaded by a compressive stress = 0.2 MPa as shown below. The material can be considered cubic with the following material properties: C11 456 GPa and C44 = = 123 GPa, C12 = 45 GPa. surfaces are fixed Calculate the: (a) Write out the elastic stiffness tensor (2 marks) (b) Stresses and strains in the material (8 marks)