The effects of glass weave on the low temperature flexure properties of composite laminates

A variety of glass fiber weaves are being considered for use in insulation materials in the International Thermonuclear Experimental Reactor central solenoid. In this study, three candidate glass weaves (1581, 7781, and 38050) were used with a Di-Glycidyl Ether of Bisphenol F (DGEBF) anhydride epoxy matrix to produce composite laminates of constant thickness. These laminates were compared at room temperature (295 K) and liquid nitrogen temperature (77 K) via three-point flexure tests. The material variables among these glass products were type of weave pattern (eight-harness satin versus plain), fiber surface treatment (epoxy compatible surface treatment versus no treatment), and cloth areal density. Based on the flexural elastic modulus and strength data at both 77 K and 295 K, the 7781/epoxy composites showed the highest values followed closely by 1581/epoxy. The 38050/epoxy performed quite poorly. The correlations of the laminate density with modulus and strength at both temperatures were almost linear. It was also found that the failure modes of samples having fibers with epoxy compatible surface treatment differed from those having no surface treatment.