第4页共6页 calculate the tensile modulus of the composite under isostrain condition?(4 pts) 0话 10 vea6瑞 A:The curve A is for isostrain condition.For a given volume fraction of fiber in a tensile modulus of the composite under isostrain condition by using the following formula: E(c)=E(f)V(f)+E(m)V(m)=E(f)V(f)+E(mX(1-V(f)) where E is the modulus of elasticity (elastic modulus)Vis volume fraction,(c)refers to the composite material,(f)refers tofibers,and (m)refers to matrix. VIII.Supplementary questions for extra points added to the total score(20pts). 1.Why is natural rubber used in automobile tires?Why are synthetic rubbers also used? (6pts Many have high hysteresis.This means hat deterioration rapidly due to great heat generated by constant flexing of automobile tires if a tire were made wholly these elastomers.In contrast.NR converts the stressing into elasticity and quickly rebounds with less heating In addition,the high hysteresis of age on wet surfaces and providing better abrasion resistance than NR.Thus rs are suitable for the tread of tires while NR is appropriate for the sidewalls第 4 页 共 6 页 4 calculate the tensile modulus of the composite under isostrain condition? (4 pts) A: The curve A is for isostrain condition. For a given volume fraction of fiber in a composite, isostrain condition is more efficient in increasing the modulus than isostress condition. If the tensile modulus of the fiber and matrix is known, we can calculate the tensile modulus of the composite under isostrain condition by using the following formula: E(c)= E(f)V(f) + E(m)V(m) =E(f)V(f) + E(m)(1-V(f)) where E is the modulus of elasticity (elastic modulus), V is volume fraction, (c) refers to the composite material, (f ) refers to fibers, and (m) refers to matrix. VIII. Supplementary questions for extra points added to the total score (20pts). 1. Why is natural rubber used in automobile tires? Why are synthetic rubbers also used? (6pts) A: Many synthetic elastomers have high hysteresis. This means that it would undergo deterioration rapidly due to great heat generated by constant flexing of automobile tires if a tire were made wholly these elastomers. In contrast, NR converts the stressing into elasticity and quickly rebounds with less heating. In addition, the high hysteresis of synthetic rubbers has an advantage in preventing slippage on wet surfaces and providing better abrasion resistance than NR. Thus, synthetic rubbers are suitable for the tread of tires while NR is appropriate for the sidewalls