FATIGUE ENDURANCE OF REINFORCED THERMOPLASTICS


PLASTICS FAIL UNDER REPEATED CYCLIC STRESS AT A LEVEL BELOW THEIR STATIC STRENGTH. THE NUMBER OF CYCLES REQUIRED TO CAUSE FAILURE IS DEPENDENT ON STRESS, TEMPERATURE, AND FREQUENCY. THE ENDURANCE LIMIT IS THE STRESS LEVEL BELOW WHICH A MATERIAL WILL WITHSTAND CYCLIC TESTING INDEFINITELY.


LISTED BELOW ARE A NUMBER OF REINFORCED THERMOPLASTICS TESTED PER ASTM D671 @ 1800 cpm.
BASE RESIN FIBER TYPE
& CONTENT		 CYCLIC FAILURE STRESS (psi)
10(4) 10(5) 10(6) 10(7)
ACETAL (CO) 30% GLASS 9000 7000 7000 7000
NYLON 6/10 30% GLASS 6800 5750 5600 5500
NYLON 6 30% GLASS 7000 6000 5750 5750
NYLON 6/6 ---- 6500 5900 5300 5200
NYLON 6/6 30% GLASS 8000 6500 6000 5900
NYLON 6/6 40% GLASS 10500 9300 9100 9100
NYLON 6/6 30% CARBON 13000 10500 8000 8000
NYLON 6/6 40% CARBON 15000 10300 8800 8500
POLYCARBONATE --- 5400 2000 1000 800
POLYCARBONATE 20% GLASS 9000 6000 5200 5000
POLYCARBONATE 30% GLASS 12500 7000 5500 5350
POLYCARBONATE 40% GLASS 14500 8750 6100 6000
POLYSULFONE 30% GLASS 14000 6500 5000 4500
POLYPROPYLENE 30% GLASS 5500 4500 4500 4500
POLYSTYRENE 30% GLASS 8000 7000 6000 5000
SAN 30% GLASS 8500 7500 6500 5500
PPS 30% CARBON 13000 9700 9500 9500
POLYESTER PBT 30% GLASS 11000 7200 5600 5100
POLYESTER PBT 30% CARBON 13000 9200 7400 6500

A RELATIVE RANKING OF GLASS REINFORCED PLASTICS FOR USE IN APPLICATIONS WHERE A GREAT MANY FATIGUE CYCLES CAN BE ENCOUNTERED IS AS FOLLOWS:

NYLON 6/6 > NYLON 6/10 = POLYCARBONATE > ACETAL > POLYPROPYLENE > POLYSULFONE = POLYSTYRENE.

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