ENGINEERING PROPERTIES OF LAMINATES 



5-37 



TABLE 5-16. FIBERGLASS POLYESTER LAMINATES 

 PER CENT WET STRENGTH FOR EXTENDED PERIOD OF IMMERSION * 



Ref. (18) 



Wet strength retention expressed as a percentage of short term 

 dry strength. Dry strength tests at 73° F and 50% Relative 

 Humidity. Wet strength tests at 73° F after immersion in water. 

 All test samples cut parallel to warp direction. 



Not available. 



When exposed to the normal range of weathering temperatures, fiberglass polyester 

 laminates do not exhibit any appreciable change in mechanical properties. In general, 

 mechanical properties are adversely affected by increasing temperature (21). 



Most laminates, particularly those used in boat hulls, are covered by paints, finishes or 

 pigmented gel coats for appearances. These coatings protect the laminate by screening out 

 the ultra violet rays and minimizing moisture absorption. Severe weathering exposure tests 

 of 3 years duration have proven the efficiency of these and other protective coatings in pre- 

 venting the deterioration of fiberglass polyester laminates. 



While extended weather exposures do cause some limited reduction in the strength pro- 

 perties of fiberglass polyester laminates, these materials are considered superior to wood 

 under long term exposure. Wood under long term weather exposure is subject to swelling, 

 cracking, dry rot, warping and fungus attack. Ferrous and some other metals not pro- 

 tected by coatings, are also subject to severe deterioration under extended weather exposure. 



Chemical Resistance: Fiberglass polyester laminates, when properly cured, are resis- 

 tant to most acids, oils and solvents. They are affected by strong alkalis, acids and chlori- 

 nated solvents (4, 22). At normal outdoor exposure temperatures, fresh and salt water, 

 gasoline and fuel oils can be stored in fiberglass polyester tanks without any deteriorating 

 effect on the laminate. 



Both fuel and potable water tanks can be constructed as integral parts of a 

 fiberglass hull structure to utilize the tank sides as stiffening for the shell. This 



