A numerical study of coupling effects of hygrothermal environment and geometrical parameter on tensile characteristic length of open-hole composite laminates

Abstract

The open-hole mechanical properties are used to evaluate the superiority of a new composite material in highly-loaded aircraft structures. The critical open-hole tensile strength and characteristic length are significantly affected by both the hygrothermal environment and width-to-hole-diameter ratio (w/D). However, the coupling effects of these two factors remain unknown until now. This paper aims to reveal the coupling effects of hygrothermal environment and w/D on the tensile strength and characteristic length of an open-hole composite laminate by using a proposed two-level finite-element-based method. Seven hygrothermal conditions, which are characterized by a non-dimensional temperature T∗, and four w/Ds are considered. The obtained results show that, both the tensile strength and characteristic length change monotonously with the variation of T∗, suggesting a considerable influence of the hygrothermal condition. Among the seven hygrothermal conditions, −55°C/dry (CTD), 23°C/dry (RTD) and 70°C/wet (ETW) are the crucial conditions. Under the CTD, RTD and ETW conditions, both the tensile strength and characteristic length are significantly increased by the rising w/D. The increase rates of tensile strength and characteristic length are insusceptible to the hygrothermal condition, and they are respectively 81% and 83% when w/D rises from 2.10 to 8.40. For a certain value of w/D, the tensile strength and characteristic length under the CTD condition are larger than those under the RTD condition, and a reverse trend is observed under the ETW condition. The resulting deviation in tensile strength is slightly related to w/D, whereas the resulting deviation in tensile characteristic length strongly depends on w/D.