ENGINEERING PROPERTIES OF LAMINATES 5-33 



M8 = 1 ply 1-1/2 ounce mat, 2 plies 25-27 ounce woven roving. 



M9 = 1 ply 1-1/2 ounce mat, 1 ply 25-27 ounce woven roving, 1 ply 3/4 ounce mat, 

 1 ply 25-27 ounce woven roving. 



M10 = 1 ply 25-27 ounce woven roving, 1 ply 3/4 ounce mat, 1 ply 25-27 ounce woven 

 roving, 1 ply 3/4 ounce mat, 1 ply 25-27 ounce woven roving. 



Test Procedures 



The test procedures, conditioning and cutting of specimens were the same as those used 

 for the basic test program with the following exceptions: 



All samples were conditioned for 48 hours at 72 degrees F and 50 per cent relative 

 humidity before being immersed in distilled water for 30 days. The shear test samples 

 were not immersed in water. 



The shear test samples were tested dry at 72 degrees F and 50 per cent 

 relative humidity. 



Per cent glass by volume and weight are determined by an Owens Corning Fiber- 

 glas test procedure instead of by the USAF method used in the basic test program. 



All flexural test specimens were cut 1 inch wide instead of the 1/2 inch width 

 specified in LP-406-b, 1031.1. 



Evaluation of Test Data 



Since the purpose of this supplementary program was to evaluate various types of lami- 

 nate constructions within a limited time, it was necessary to restrict the scope of this pro- 

 gram to a minimum number of test panels and specimens which would provide maximum 

 data. All of the panels were fabricated and tested by a single laboratory. These panels 

 were made with one polyester resin and only one panel was made for each type of lami- 

 nate construction. 



The effects of differences in fabricators, laboratories and thicknesses could therefore 

 not be evaluated in this program and only the effect of variations in laminate reinforcements 

 was obtained. 



Simple average values without confidence limits were determined from 5 tests per 

 property, per specimen, per direction except for moduli values which were taken on 

 two specimens. 



FACTORS AFFECTING ENGINEERING PROPERTIES 



In addition to the type of reinforcement and molding method used, shop practice, 

 environmental conditions and duration of loading are other primary factors affecting the 

 engineering properties of fiberglass reinforced laminates. 



Careless production methods which lack proper handling and storage of basic materials 

 and adequate quality control will produce laminates with defects that will reduce the engineer- 

 ing properties of the laminates. All fabricators should investigate their facilities and molding 

 operations to improve their production methods and quality of their products. 



