Evaluation of mechanical behaviour of unidirectional fibre-reinforced composites considering the void morphology

Abstract

Voids are one of the most common defects in fibre-reinforced composite materials. Insightful understandings of the correlation between void morphology and material properties can benefit the desired performance of industrial products. A two-level analysis method for unidirectional fibre-reinforced composites containing voids is developed based on micromechanical modelling. Representative volume cells at different levels are developed based on the description of fibre distribution and void geometry. Finite element analysis was performed on the representative volume cell to determine the effective elastic moduli. Good agreements are found among the finite element analysis results, theoretical results of Halpin-Tsai equation and experimental characterization from literature. Results show that the mechanical properties of composites are significantly affected by void morphology. Larger width-height aspect ratio leads to a less modulus reduction of in-plane modulus, but it produces larger reduction of out-of-plane modulus. Moreover, the finite element analysis results can give good explanation to the discreteness of the experimental characterization. It indicates that typical voids that are formed in the autoclave process have significant impact on the out-of-plane modulus. The study considered the temperature effect on the composite containing voids. Results show that there is no coupling effect between porosity and temperature.

Voids formation and their effects on mechanical properties in thermoformed carbon fiber fabric‐reinforced composites

“…Extensive studies have shown that voids content leads to a significant decrease in composites’ mechanical properties, especially those dominated by the resin matrix behavior such as flexural strength, and ILSS . Certainly, the mechanical properties are also closely related to the fiber volume fraction and laminate with the larger volume fraction exhibits higher strength and modulus within a certain range.…”

3-Phase hierarchical graphene-based epoxy nanocomposite laminates for automotive applications

“…Studies of fractured surfaces showed that a smooth, featureless surface is attributed to brittle failure, while rougher fracture surfaces are attributed to tougher nanocomposites [52]. Furthermore, the fractured surface of sample CF-A-0.8Gr-AVA clearly shows the presence of micron-size voids, a common type of defects, arising from the manufacturing process [53]. It is suggested that the mechanical properties are negatively affected by increasing porosity which is correlated with the decrease of GIC in the case of the Gr-AVA samples having significantly larger voids.…”

State‐of‐the‐art review on developing lightweight fiber‐metal laminates based on synthetic/natural fibers

“…When scrutinizing the internal structures, voids typically form in the interlaminar regions of composite laminates. [136][137][138] Voids in FMLs during the VARTM process exist because the vacuum pump alone does not generate sufficient pressure to evacuate them. Thus, additional high pressure is generally required to purge the interlaminar voids.…”

“…Furthermore, the VARTM process cannot attain the high‐performance level of the autoclave process. When scrutinizing the internal structures, voids typically form in the interlaminar regions of composite laminates 136–138 . Voids in FMLs during the VARTM process exist because the vacuum pump alone does not generate sufficient pressure to evacuate them.…”