Temperature effects on mixed mode I/II delamination under quasi-static and fatigue loading of a carbon/epoxy composite

Abstract

© 2015 The Authors.Abstract This paper addresses the effect of temperature on the mixed-mode interlaminar fracture toughness and fatigue delamination growth rate of a carbon-fibre/epoxy material, namely IM7/8552. Quasi-static and fatigue characterisation tests were carried out at -50 °C, 20 °C, 50 °C and 80 °C, using asymmetric cut-ply coupons. The experimental results show that temperature may have an accelerating or delaying effect on delamination growth, depending on the loading regime, i.e. either quasi-static or fatigue. Fractographic examinations were also carried out in order to assist the interpretation of the experimental data. A semi-empirical equation is introduced to describe the experimentally observed fatigue delamination growth rates at elevated temperatures

Mixed Mode I/II interlaminar fracture toughness of carbon Fiber/RTM‐6 laminates manufactured by VARTM

“…) it is possible to conclude that they have the same length about 1.6 ± 0.13 mm, confirming that the stick‐slip behavior is directly related to the fabric architecture. Some variations in toughness values and stick‐slip shape for the material system studied herein may be attributed to several factors such as resin‐rich or fiber‐rich regions along the longitudinal direction, misalignment of the fibers and voids, as well as fiber waviness, void and fiber breakage . The stick slip behavior may also be interfered by the equipment set up.…”

“…. According to open literature the increase of toughness value at cryogenic temperature can be promoted by two different factors: one is influenced by the failure mechanism knew as fiber breakage and other could be influenced by the addition of fillers into the matrix to increase the toughness at cryogenic temperatures. Using the SEM analyses was possible to notice that the factor‐contributing to increase the toughness at cryogenic temperature for the material studied in the present work was the fiber breakage.…”

“…The fracture toughness values may have increased at cryogenic temperature due to this deviation in the crack propagation front direction . Besides that, it is possible to observe a significant amount of matrix was still attached on the fibers (fiber surrounded by resin) when the fiber breakage occurs, this also can result in an increase in toughness so the crack continues propagating .…”

“…a[C] and c[C]) due to fiber debonding. However, as the Mode II component increases, the cracks are reoriented and they develop an angle to the laminate plane under pure Mode II (Fig. a[D] and c[D]), for this reason, it is possible to observe cusps formation (Fig.…”

Static and Fatigue Delamination

“…In the literature several cases are presented where the upper limit coincides with approximately 0.7-0.8 times the G Ic [35,36].…”