A Review of Damage Tolerance and Mechanical Behavior of Interlayer Hybrid Fiber Composites for Wind Turbine Blades

Abstract

This review investigates interlayer hybrid fiber composites for wind turbine blades (WTBs), focusing on their potential to enhance blade damage tolerance and maintain structural integrity. The objectives of this review are: (I) to assess the effect of different hybrid lay-up configurations on the damage tolerance and failure analysis of interlayer hybrid fiber composites and (II) to identify potential fiber combinations for WTBs to supplement or replace existing glass fibers. Our method involves comprehensive qualitative and quantitative analyses of the existing literature. Qualitatively, we assess the damage tolerance-with an emphasis on impact load-and failure analysis under blades operational load of six distinct hybrid lay-up configurations. Quantitatively, we compare tensile and flexural properties-essential for WTBs structural integrity-of hybrid and glass composites. The qualitative review reveals that placing high elongation (HE)-low stiffness (LS) fibers, e.g., glass, on the impacted side reduces damage size and improves residual properties of hybrid composites. Placing low elongation (LE)-high stiffness (HS) fibers, e.g., carbon, in middle layers, protects them during impact load and equips hybrid composites with mechanisms that delay failure under various load conditions. A sandwich lay-up with HE-LS fibers on the outermost and LE-HS fibers in the innermost layers provides the best balance between structural integrity and post-impact residual properties. This lay-up benefits from synergistic effects, including fiber bridging, enhanced buckling resistance, and the mitigation of LE-HS fiber breakage. Quantitatively, hybrid synthetic/natural composites demonstrate nearly a twofold improvement in mechanical properties compared to natural fiber composites. Negligible enhancement (typically 10%) is observed for hybrid synthetic/synthetic composites relative to synthetic fiber composites. Additionally, glass/carbon, glass/flax, and carbon/flax composites are potential alternatives to present glass laminates in WTBs. This review is novel as it is the first attempt to identify suitable interlayer hybrid fiber composites for WTBs.

Keywords: composite structures; damage tolerance; fiber hybridization; low-velocity impact; mechanical properties; wind turbine blade.

Figure 7

Schematic of different hybrid lay-up configurations of interlayer hybrid composites (rectangles are intended for illustration and do not represent an exact number of layers).

Figure 1

The fishbone diagram of impact loads and impact-susceptible regions in a wind turbine blade [12].

Figure 2

An overview of the kinetic energy and velocity of different accidental and operational impact loads in WTBs (data obtained from [12]).

Figure 3

The breakdown of fiber hybridization. A schematic of a hybrid composite with four layers is provided next to each hybrid fiber configuration: (a) Interlayer (sandwich), (b) interlayer (intercalated), (c) intralayer, and (d) intrayarn.

Figure 4

An overview of the methodology used in this review.

Figure 5

Key elements of the DTD framework (adapted from [17]).

Figure 6

The relation between damage size and residual strength [17].

Figure 8

Schematic of the most frequent EAMs in a composite laminate subjected to LVI (adapted from findings in [111,115,116]).

Figure 9

A schematic of a composite laminate subjected to tensile, flexural, compressive, impact (side-view), and shear (top-view) loads (solid arrows indicate the direction of the applied load).

Figure 10

Schematic stress-strain curve representation of LE-HS, HE-LS, and hybrid composites and the expected role of the synergistic effect in delaying the failure of the hybrid composite (adapted from [32]).

Figure 11

Tensile properties of hybrid and non-hybrid composites (the average value is given at the top of each bar chart and the error bars indicate the standard error of the mean (SEM). The number of samples, n and SEM for each label is given in the table).

Figure 12

Flexural properties of hybrid and non-hybrid composites (the average value is given at the top of each bar chart and the error bars indicate the standard error of the mean (SEM). The number of samples, n and SEM for each label is given in the table).

Figure 13

A comparison between (a) tensile strength and (b) tensile modulus of glass and other hybrid composites. The first number indicates the average tensile property, followed by the standard error of the mean (SEM) in brackets and number of samples in parenthesis (MATLAB code obtained from [190]).

Figure 13

A comparison between (a) tensile strength and (b) tensile modulus of glass and other hybrid composites. The first number indicates the average tensile property, followed by the standard error of the mean (SEM) in brackets and number of samples in parenthesis (MATLAB code obtained from [190]).

Figure 14

A comparison between (a) flexural strength and (b) flexural modulus of glass and other hybrid composites. The first number indicates the average flexural property, followed by the standard error of the mean (SEM) in brackets and number of samples in parenthesis (MATLAB code obtained from [190]).