6-34 



DESIGN OF LAMINATES 



,uiuiii;uuniiii 



1 



IIIHIIUHI tl IMtMl 



p 



.1/2" 



! 



Fig. 6-23. Woven Roving 

 Laminate in Compression 



From Table 5-11 the ultimate compressive strength, F c , selected is 9600 psi. 

 The allowable design stress, based on a factor of safety of 2, is then: 



9600 

 f = -x— = U800 psi 



Then; 





35000 

 U800 



7.29 sq.in. 



(6. 12e) 



and; 



A 



t 



7.29 

 0.50 



= lit. 58 in. 



Column Characteristics of Laminates 



When the length of the compression member is such that buckling will occur, the critical 

 load, P cr , can be calculated with equation 6. 12 provided that the ultimate stress, F c , is 

 reduced to allow for the unsupported length of the member (13). Structural members, in 

 the buckling range, can be divided into two groups, namely: 



1. Members in which the compressive stress is less than the proportional limit 



of the material or follows Hooke's Law under a critical load P 



cr* 



2. Members in which the compressive stress exceeds the proportional limit of the 

 material, under a critical load P cr . 



If the member is in the first group the following equations can be used to determine 



the load P 



cr- 



cr 



(6. 17) 



(6. 17a) 



(If 



