4 



Materials and Molding 



Methods 



MATERIALS 



Fiberglass laminates are essentially a combination of high strength glass fibers bonded 

 together with relatively low strength resin. The glass fibers are distributed throughout the 

 laminate and provide the strength to the combination. Although individual glass filaments 

 can develop tensile strengths between 250, 000 and 400, 000 pounds per square inch, the 

 mechanical distribution of the filaments in a laminate does not permit the combination to 

 develop this strength. 



Structural laminates usually contain 2 to 60 per cent by weight of fiberglass reinforce- 

 ment. The strength of a laminate is primarily dependent upon the type and the amount of 

 fiberglass reinforcement it contains. The amount or per cent of fiberglass reinforcement 

 that can be placed in a laminate depends upon the molding process and type of reinforcement. 



Other important factors affecting the strength of a laminate are the resin, chemical 

 finish on the fiberglass filaments (1,2) and the handling of these basic materials. 



The selection of the type of reinforcement, resin and molding method should be made to 

 meet the necessary requirements for a specific application. High unit strengths, compara- 

 ble to other engineering materials such as wood, aluminim and steel, can be developed. 



To obtain high stiffness weight ratio economically, molded-in stiffeners or sandwich 

 construction are used. Sandwich panels are usually made by bonding fiberglass laminate 

 facings to various low density core materials such as honeycomb, foam plastics, balsa wood 

 and lightweight plastic spheres embedded in resin (3, 4). 



Due to the rapid development and modifications of basic materials and molding methods, 

 changes in the cost of materials, and variation of laminate construction will continuously 

 occur in the future. Since such changes cannot be considered within the scope of this text, 

 the following discussion is limited to presently available materials and molding methods. 



To obtain maximum efficiency and economy, selection of basic materials and molding 

 methods for specific applications should be in accordance with manufacturers' recommenda- 

 tions. 



REINFORCEMENTS 



The glass filament used in boat hull construction is a lime -alumina borosilicate E 

 glass of low alkali content which has high chemical stability and moisture resistance. It 

 is commonly known as E glass because of its initial development for electrical applications. 



4-1 



