Modeling of Compressive Strength for Unidirectional Fiber Reinforced Composites with Nanoparticle Modified Epoxy Matrix

Abstract

Incorporation of nanoparticles into polymer matrix was found to considerably improve the compressive performance of unidirectional fiber reinforced composites. In our experimental study, an increase by 62.7% in the longitudinal compressive strength of unidirectional carbon fiber reinforced composites is attained by dispersing 8.7 vol.% SiO2 nanoparticles into epoxy matrix. A compressive strength model is established to quantitatively describe the reinforcing effects of nanoparticles, which combines a modified microbuckling model for unidirectional fiber reinforced composites and a constitutive model for nanocomposite matrices under compression. In the two models, the coupling of damage and plasticity is considered to contribute to the nonlinear response of nanocomposite matrix. The proposed strength model demonstrates excellent prediction capability in experimental verification. A small relative deviation below 8.2% is achieved between the predicted compressive strength of unidirectional fiber reinforced composites and the measured values, which is at the same level of random error in experiments.

A Review on Mechanical Performance of Hybrid Natural Fiber Polymer Composites for Structural Applications

“…The configuration of fibers in a composite’s system plays a major role affecting the compressive properties of the hybrid composites. Chen et al [ 120 ] mentioned that unidirectional fiber-reinforced composites have inferior compressive properties due to the shape instability of the fiber especially at a high aspect ratio. The microbuckling of fibers can occur at a stress level considerably below the strength of the fiber followed by I kinking of fibers, and matrix-tuning is an approach to enhance the compressive strength of unidirectional fiber-reinforced composites.…”

Enhancing the Longitudinal Compressive Strength of Freeform 3D-Printed Continuous Carbon Fiber-Reinforced Polymer Composite Laminate Using Magnetic Compaction Force and Nanofiber Z-Threads

“…Table 4 compares the longitudinal compressive strength values of unidirectional (0 • ± 5 • ) laminates from this study with those of 2 • and 10 • offaxis misaligned carbon fiber/nano-SiO 2 /epoxy composites produced via vacuum-assisted resin transfer molding (VARTM) processes. These composites include varying volume fractions (0 vol%, 1.1 vol%, and 8.7 vol%) of nano-SiO 2 to reinforce the matrix [20]. The comparison indicates that the longitudinal compressive strength of the 2 • off-axis 8.7 vol% nano-SiO 2 -reinforced T700 CFRP/VARTM case is similar to, albeit slightly lower than, the AS4 CFRP/MCFA-AM (0.5 bar) case.…”

“…In theory, a higher fiber volume fraction (FVF) leads to nearly linearly increased tensile strength, although this may not hold true for the compressive strength of the composite. The compressive strength, highly susceptible to fiber buckling failure micromechanics, is also significantly influenced by factors such as the matrix material, presence of voids, and the bonding between the matrix and fibers, and even a few degrees of the off-axial angle of the carbon fiber misalignment [20], especially if no nanoparticle reinforcement is considered. Equation ( 1) can be applied to calculate the fiber volume fraction (FVF) of an FRP prepreg:…”

“…While the micromechanics cannot be fully investigated by this experimental study, the experimental discovery shows that it would be of interest for future numerical analysis (such as finite element analysis) to further understand the micromechanics details, especially for CNF Z-threaded CFRP. According to [20], the SiO 2 nanoparticles can help increase the elastic modulus of the epoxy matrix, thus helping stabilize the carbon fibers to delay the fiber micro-bucking under the longitudinal compression. Following the same rationale, one can also expect the CNF z-threads embedded inside a CFRP can enhance the elastic support given to the carbon fibers and mitigate fiber micro-buckling, and the elastic support provided by the CNF z-threads could likely be increased with a higher compaction pressure applied during the manufacturing process or a ZT-CFRP laminate with a lower resin content.…”

“…With further improvements to the control system and resin shelf life, MCFA-AM could meet or even surpass OOA-VBO in producing high-quality CFRP composites. Table 4 showcases the comparative compressive strength values of the unidirectional (0 • , with an estimated uncertainty of ±5 • ) laminates from this paper and off-axial strength values of CF/nano-SiO 2 /epoxy composites [20]. Table 4 compares the longitudinal compressive strength values of unidirectional (0 • ± 5 • ) laminates from this study with those of 2 • and 10 • offaxis misaligned carbon fiber/nano-SiO 2 /epoxy composites produced via vacuum-assisted resin transfer molding (VARTM) processes.…”