Abstract
Composites made of S2 glass fibers and toughened epoxy with various lay-up configurations ([0°]24, [0°2/90°2]3S, [45°2/−45°2]35, and [0°3/45°3/90°3/−45°3]S) were tested under uniaxial tension at various temperatures from −60 to 125°C. The stress-strain curves are distinctly nonlinear, which can be attributed to various types of damage progression. Fiber breaks, fiber-matrix debonding, and fiber pull-out characterized damage in the [0°] and [0°/90°] specimens, which have stress-strain relations resembling those for quasi-brittle materials. Shear failure and delamination were dominant in the [±45°] specimens and resulted in stress-strain curves similar to those of quasi-ductile materials. The tensile behavior of the [0°/45°/90°/−45°] specimens, as expected, laid in between the two extremes. In addition to stacking sequence, temperature also exerted great influence on the stress-strain behaviors of these composites. In general, specimens tested at lower temperatures behaved more stiff and brittle than those tested at higher temperatures. Finally, micromechanics-based finite element analyses were conducted to verify the afore-mentioned various failure modes.
