Influences of in-plane and out-of-plane fiber waviness on mechanical properties of carbon fiber composite laminate

Abstract

Based on the curing process of carbon fiber/epoxy prepreg with autoclave, two kinds of unidirectional carbon fiber laminates with in-plane and out-of-plane waviness were fabricated by rolling prefabricated out-of-plane waviness and inserting prepreg strip, respectively. Fiber waviness defects in composites were characterized by waviness ratio. The specimens containing fiber waviness were successfully prepared with almost the same fiber content and low porosity. The influences of fiber waviness with different waviness ratio on tensile, compressive, and charpy impact properties of unidirectional laminates were studied, and the corresponding failure modes were observed. The mechanism of the effects of fiber waviness on mechanical properties was discussed. The experimental results show that tensile property and compressive property decrease by in-plane buckling and out-of-plane wrinkling, especially with large waviness ratio. Reduction of 33.0% of compressive strength with out-of-plane wrinkling is seen in the case of 0.037 waviness ratio, while 25.4% reduction is obtained for in-plane buckling under 0.038 waviness ratio. Charpy impact strength decreases by in-plane buckling, whereas increases by out-of-plane wrinkling. Failure morphologies of various specimens are changed by fiber waviness, which are consistent with the mechanical degradation. In addition, there are some differences on the sensitivity of mechanical properties to different types of fiber waviness. Tensile strength is more sensitive to in-plane buckling in comparison with out-of-plane wrinkling, and compressive property is more sensitive to out-of-plane wrinkling.

Effect of the attitude fine-adjustment of compaction roller on automated fiber placement defects and trajectory

“…The fiber pull-up is similar to the wrinkling (buckling) and has important influence on composites mechanical performance. 29–33 When the fiber is deposited on a curved path, it will result in compressive forces and tensile forces applied through the width of the fiber. If tensile forces are too high, fiber will be lifted beyond the mandrel surface on the outside the steered tow.…”

An Experimental and Numerical Investigation to Characterize an Aerospace Composite Material with Open-Hole Using Non-Destructive Techniques

“…All these processes belong to autoclave manufacturing methods, and each of them produces different manufacturing fiber, waviness defects being one of the most relevant [ 4 , 5 , 6 ]. The waviness is produced due to the axial compression of the fibers by the non-uniform pressure distribution between films and has a predominant effect on mechanical properties such as tensile, compressive, flexural and fatigue strength, being one of the most studied defects in the literature [ 7 , 8 , 9 , 10 , 11 ].…”

Influences of out-of-plane fiber waviness on the curved beam strength of glass fiber composite laminates

“…Wang et al [24] developed the transverse strip method and the ply-drop method for the outof-plane waviness. Placing a thin rod at the interface between plies was another frequently used method to generate in-plane and out-of-plane fiber waviness [17], [27]- [29]. In order to generate out-of-plane waviness, Hasiao and Daniel [22] and Allison et al [25] stacked plies that were pre-cured on curved mold between plies pre-cured on flat mold, thus, local out-ofplane fiber waviness were obtained between the flat plies.…”

“…Therefore, the influence of fiber waviness and wrinkling on the mechanical properties of the parts should be considered. Many studies were conducted to establish an appropriate manufacturing technique to generate artificial inplane fiber waviness [16]- [23], and out-of-plane fiber waviness [16], [17], [24]- [30] and to measure the degradation ratio of the mechanical properties. Wang et al [24] developed the transverse strip method and the ply-drop method for the outof-plane waviness.…”

“…First, prepreg plies were laid down on a flat mold, and then the stacked plies pressed into L-shaped mold causing the fibers on the inner side to buckle. Wu et al [17] measured the effect of inplane and out-of-plane fiber waviness on tensile, compressive, and impact properties of the flat laminate. It was found that both in-plane and out-of-plane waviness significantly reduced the compressive properties.…”