Evaluation of Tensile Strength of Woven Carbon/Epoxy Composite Laminates at Cryogenic Temperatures Using the Open Hole Specimens

Abstract

We propose a combined numerical-experimental method for the evaluation of the tensile strength properties of woven carbon fiber reinforced polymer (CFRP) composite laminates at cryogenic temperatures using the open hole specimens. Cryogenic tensile tests were conducted on the open hole specimens of quasi-isotropic woven CFRP laminates, and the length of the hole edge damage zone corresponding to the specimen failure was determined by the microscopic examinations of failed specimens. A finite element based method was developed for estimating the cryogenic tensile strength of the unnotched woven laminates using the experimentally determined failure load and damage zone length. In the damage zone, the material was assumed to carry a uniform normal stress equal to the tensile strength. The results demonstrate that the present method is an efficient approach to measuring the tensile strength of high-strength advanced composites at cryogenic temperatures.

Properties of cryogenic and low temperature composite materials – A review

“…dog bone instead of rectangular [270]) to those specified by standards, therefore increasing the sensitivity of specimens to boundary conditions such as free-edge effects and clamping [78]. Several authors reported inconsistency in material properties measured at CT in the literature [22,55,124,271], and the deviation from standards is believed to be one reason for this. achieved reduced fixture size by a self-designed jig [273].…”

“…1b) is shattered into several chunks due to its ductility and subsequent redistribution of load after local fibre failures. Poisson's ratio should become lower with decreasing temperature due to the increased stiffness of the resin [70], but several authors reported increased values at CT [45,55,59,60]. A possible explanation can be the difference in increase in longitudinal (𝐸 1 ) and transverse (𝐸 2 ) elastic modulus.…”

“…Charalambous et al used asymmetric cut-ply coupons for fatigue delamination growth measurement, as this configuration does not need monitoring of the delamination length during fatigue testing[108]. Shindo and his co-workers proposed using open hole testing for indirect measurement of tensile strength, as these specimens fail at lower load and are not affected by the stress concentration near clamping[55,272]. Shindo et al noted that compact tension coupons are preferred because they require the least amount of test material to evaluate crack growth behaviour[22].Pan et al …”