Initiation of structural defects in carbon fiber reinforced polymer composites under hygrothermal environments

Abstract

Exposure to hygrothermal environments affects mechanical properties of laminated composites through two principle mechanisms, namely, moisture absorption and the structural deterioration due to it. Previous studies have indicated that moisture plays a positive role in carbon fiber reinforced polymer composites by alleviating their damage under impact. In this study, carbon fiber reinforced polymer composites were exposed to long-term hygrothermal ageing to investigate the possibility of the initiation of structural defects due to it and their influences on the various behaviors of the laminated composites. A major type of observable structural defects was identified and the related initiation mechanism was proposed. It was found for the first time that the structural defects formed during hygrothermal ageing in turn changed the moisture uptake profile of the laminated composites. The effects of structural defects on the impact resistance of carbon fiber reinforced polymer composites were exclusively evaluated after removing the absorbed moisture. Tensile testing on vacuum-oven-dried laminates was conducted to assist the understanding of the mechanical strength of the carbon fiber reinforced polymer composites exposed to the hygrothermal environments.

Prediction of the mechanical behavior of flax polypropylene composites based on multi-scale finite element analysis

“…The coefficient of variation for tensile strength of flax/polypropylene composites is 9.78%. It was reported that the coefficient of variation for the tensile strength of carbon fiber composites was 3.49% [30]. Such coefficient of variation for glass fiber composites was reported to be 6.93% [31].…”

Multilayer Structural Diagnosis With Quasi-3d Microwave Imaging Using Ultrawideband Radio Frequency Noiselet Waveforms

“…Addressing the actual delaminations on FRP composite structures, Fig. 7 depicts defects caused due to hygrothermal environment [18]. It provides cross-sectional images showing the difference between unidirectional FRP samples without delaminations and with delaminations after immersing in water at 80 • C for 6 months.…”

“…It was noted that delaminations occurred in lateral directions within the range of (a) (b) centimeters; thus these structural characteristics of delaminations are investigated using our approach for both scale and depth detection. Delaminations can also be caused by moisture uptake in FRP laminates [18]. Interlaminar shear stress appear when the adjacent plies are ready to expand along different directions as a result of moisture uptake, as shown in Fig.…”

Predictive Model for Tensile Properties of Carbon Fiber-Reinforced Polymers at Various Moisture Contents

“…The size of the cavities is in the order of 10 -7 to 10 -6 m (Gdoutous 1993). Figure 1 shows an scanning electron microscope (SEM) image of the cross-section of a CFRP laminate after hygrothermal conditioning; and cavities with the size of microns can be observed (figure taken from (Zhong and Joshi 2015)). The clustering of water molecules results in the polymer molecules near the sub-micro-cavities to have a high chance of interacting with the water molecules.…”