6-84 



DESIGN OF LAMINATES 



The values of E]_, and Et, modulus of elasticity, in the L and T direction respective- 

 ly, were assumed to be constant throughout the range of the stress-strain curve. 

 For the laminates tested this assumption appears valid since the stress-strain 

 curves are almost straight lines. 



Since fiberglass laminates do not exhibit a true proportional limit, the values used 

 were ultimate values obtained by testing. 



The panels were considered loaded along the "a" dimension with the warp fibers 

 running parallel to the "b" dimension. 



For the development of Tables 6-4 through 6-15, the following low average values from 

 the tables in Chapter 5 were used: 



2 Oz. Mat 



Ultimate Flexural Stress (Table 5-9) 



s F bL = F bT " 20,500 psi 



25-27 Oz. Woven Roving : F bL = F bT = 28,200 psi 

 10 Cz. Cloth : F bL = F bT = 31,100 psi 



Flexural Modulus of Elasticity (Table 5-10) 

 2 Oz. Mat : E L = 0.86 x 10° psi- E T = 0.86 x 10° psi 



25-27 Oz. Woven Roving : E L = 1.81 x 10° psi E T = 1.5b x 10° psi 



10 Oz. Cloth 



,6 



E T = 1.96 x 10° psi 



Ju 



,6 



F cL = F cT = 19 > 2 °° pSi 



T = 1.70 x 10° psi 

 Ultimate Compressive Stress (Table 5-11) 



2 Oz. Mat 



25-27 Cz. Woven Roving : F cL = F cT = 19,200 psi 



10 Oz. Cloth : F cL = F cT = 18,900 psi 



Ultimate Shear Stress, Parallel (Table 5-14) 



2 Oz. Mat : F sL = F sT = 10,100 psi 



25-27 0z. Woven Roving : F s l = F s ? = 9,500 psi 

 10 Oz. Cloth : F sL = F gT = 10,500 psi 



Shear Modulus 

 (Table 5-14) 



Poisson's Ratio 

 (Tables 5-8 and 5-13) 



2 Oz. Mat 



25-27 0z. Woven Roving : G 



: G LT = O.IiO x 10 u psi 



LT 



10 Oz. Cloth 



G. 



LT 



0.U5 x 10 u psi 

 0.52 x 10 psi 



°LT =°TL = - 37 

 °LT =°TL = - 19 



a LT o TL 



= 0.20 



