5-36 



ENGINEERING PROPERTIES OF LAMINATES 



Figs. 5-15 and 5-16 give the relationships between fiberglass content, per cent voids and 

 wet strength retention for 10 ounce cloth and 25-27 ounce woven roving with silane finishes. 

 The graphs in these Figures, developed from limited data (19), indicate that laminates with 

 fiberglass contents within the average fabrication ranges have wet strength retentions of 

 approximately 80 to 95 per cent with the exception of compressive strength which has ap- 

 proximately 50 to 80 per cent retention. Laminates with lower fiberglass contents than the 

 average fabrication range have higher percentages of wet strength retention even though 

 they have lower initial strengths. 



3 Z 



a 



*- m 



in > 



< 



I- Q 



5 o 



t- o 



10 20 30 40 50 60 70 80 90 100 

 WEIGHT PERCENT FIBERGLASS 



10 20 30 40 SO 60 70 80 90 10 

 WEIGHT PERCENT FIBERGLASS 



Fig. 5-15. Fiberglass Polyester Lami- 

 nates - Contact Molded 10 Oz. Cloth 

 with Silane Finish. Relationships Between 

 Fiberglass Content, Per Cent Voids and 

 Wet Strength Retention 



Fig. 5-16. Fiberglass Polyester Lami- 

 nates - Contact Molded 25-27 Oz. Woven 

 Roving with Silane Finish. Relationships 

 Between Fiberglass Content, Per Cent 

 Voids and Wet Strength Retention 



Equivalent data for fiberglass mat laminates relating fiberglass content, per cent voids 

 and wet strength retention are presently not available. Limited data indicates that fiberglass 

 mat laminates with silane finish on the reinforcement and fiberglass content within the 

 average fabrication range, have wet strength retentions of approximately 80 to 95 per cent 

 for most of the mechanical properties. 



Recent tests on fiberglass polyester laminates immersed in water for one year have 

 been conducted (18) and the results are given in Table 5-16. 



In most instances, laminates subjected to extended periods of continuous water immer- 

 sion will have reduced percentages of wet strength retention. When properly coated with an 

 effective paint or the more commonly used pigmented gel coat, fiberglass polyester lami- 

 nates used in boat hull construction will satisfactorily resist the adverse affects of exposure 

 to normal environmental conditions. 



Weathering: Clear or translucent fiberglass polyester laminates exposed to direct sun- 

 light and weather over a period of years will tend to yellow and show some reduction in 

 mechanical properties. Fire-retardant resins containing chlorine in their molecular 

 structure will deteriorate at a faster rate (20). Ultra-violet rays contained in the sunlight 

 are considered to be the chief cause of weather deterioration. 



