Fatigue of fibre-reinforced plastics due to cryogenic thermal cycling

Abstract

Due to the different thermal expansion of the constituent materials, cyclic thermal loading of fibre reinforced plastics induces alternating stresses in the material at two scales: (1) at the microscale (level of fibre–matrix-interaction) and (2) at the macroscale (level of the multidirectional laminate). Especially the effect of the thermal-induced stresses at the microscale is not comprehensively investigated yet. In the present paper, the effects of both scales are analysed. For the investigation of the microscale effect, unidirectional laminates are thermally cycled between 293 K and 90 K up to 1000 times. Afterwards, by mechanical tests at room temperature, the elasticity and strength properties in the different material directions are determined as function of the number of thermal cycles. Additionally, thermally cycled specimens are microscopically investigated in order to observe the matrix crack forming process at thermal fatigue loading. Contrary to the expectations, no significant matrix cracking and therefore no significant reduction of the elasticity and strength properties due to the thermal cycling are observed. In order to analyse the effect of the superposition of the thermal-induced stresses on micro- and macroscale, cross-ply laminates are investigated in the same manner. In these laminates matrix cracks are detected after 1000 cycles, which, however, do not reduce the stiffness and strength of the cross-ply laminates.

Numerical prediction of the ballistic performance of hygrothermally aged CFRP laminates using a multi-scale modelling approach

“…(b), in line with the thermal cycling results in[1]. Initial fibre-matrix interface damage (a) and transverse matrix cracks (b).…”

“…Cyclic loading and environmental conditions during the lifetime of CFRP components can have significant negative effects on their material properties and performance. Previous studies on mechanical fatigue, hygroscopic absorption, temperature and thermal cycling have shown reductions in stiffness, strength, fracture toughness properties can be caused by a combination of chemical changes in the constituents and different types of damage, including micro-damage at the fibre-matrix interfaces (and/or toughening particles) as well as larger scale matrix cracking and/or delamination [1,2].…”

Properties of cryogenic and low temperature composite materials – A review

“…Finally, the plateau is present because the matrix cracks relieve the stress concentrations in the material [119]. Other authors experienced first decreasing, then increasing, then plateauing properties [116,117,140]; constantly decreasing properties [117,135,[141][142][143][144], constantly increasing [47], and unchanged properties [135,145,146].…”

A review on critical aspects of thermal shocks and thermal cycles in fiber reinforced polymer composites

“…Moreover, for off-shore construction or aeronautics, investigating the effects of cyclic freeze–thaw conditions on mechanical response of FRPCs are vital. 63,64 An aircraft which descends from a cryogenic temperature of sky, i.e., −50 o C, to the ground levels with atmospheric temperature of 30 o C, is frequently exposed to thermal cycles and thermal shocks. 65 Therefore, clarification of the influences of temperature conditions such as thermal cycles and thermal shocks on mechanical response and efficiency of FRPCs is of great importance.…”

“…Most research works have followed thermal cycle regimes that the composite material during life-time would experience under a specific environmental condition of interest. However, Lüders and Sinapius 64 conducted a research considering the operational conditions of repeated refueling and discharge of hydrogen storage tanks exposed to cyclical thermal and mechanical loading. They investigated the effects of thermal cycles (293 K and 90 K up to 1000 cycles) on elasticity and strength of unidirectional and multidirectional FRPCs.…”