Effects of various porosities on the damage evolution behavior of carbon fiber/epoxy composites using acoustic emission and micro-CT

Abstract

Void defects can reduce the mechanical properties of composites and increase the potential danger of composite components in service. The effects of various porosities on damage evolution behaviors of carbon fiber/epoxy composites are deeply investigated by combining the damage visualization and acoustic emission response. The results showed that the increased porosity accelerates the damage evolution from micro-scale to macro-damage. Acoustic signals in composites are captured in advance when the porosity is high, and the voids below the kink band accelerate matrix cracking and delamination, while specimens with low porosity easily cause fiber damage and fiber/matrix debonding. Additionally, applying extra pressure during the resin transfer molding process can decrease the porosity, but excessive extra pressure may result in an inverse result. The method combining acoustic emission and micro-CT can provide a reference for improving quality and the health monitoring of composites.

Effect of hybrid ratio on shape memory properties of graphene oxide‐carbon/glass fiber composites prepared based on vacuum infiltration hot‐press forming experimental system

“…Moreover, the interfiber bonding in the C6 specimen was too tight, and the local stress was difficult to be dispersed, and a slight fracture of CF occurred during bending and shaping (see Figure 8B). 24 Coupled with the fact that the fibers are prone to kinking, pulling out and other defects during the subsequent cyclic testing of multiple shape memory performance cycles, the probability of the length of the fiber bundle decreasing increases, and thus the probability of fiber fracture is improved, and a certain degree of fatigue accumulation occurs in the shape memory composites, all of which lead to specimen cracking and swelling.…”

Influence of extrusion pressures on shape memory properties of carbon fiber/basalt fiber hybrid composites with graphene oxide fabricated by the vacuum infiltration hot pressing system

“…With the increase of extrusion pressure, the infiltration of resin solution containing GO in the fiber bundles was smoother, the microstructure improved, and the properties also improved. However, when the extrusion pressure was 0.7 MPa and it was large, pores were generated at the fiber‐matrix interface, preventing resin from impregnating the fiber and resulting in weaker adhesion between the fiber layers 18 . In the shape memory property test, GO‐CF/BF hybrid composites experienced heating softening and cooling solidification.…”

“…However, when the extrusion pressure was 0.7 MPa and it was large, pores were generated at the fiber-matrix interface, preventing resin from impregnating the fiber and resulting in weaker adhesion between the fiber layers. 18 In the shape memory property test, GO-CF/BF hybrid composites experienced heating softening and cooling solidification. Because of the different coefficients of thermal expansion of polymer matrix and fiber, the stress caused by strain led to interfacial debonding between fiber and matrix.…”

“…This was due to large extrusion pressure and short infiltration time, and there was more time for the relaxation of the matrix layer. Wang et al 18 studied the effect of different extra pressures on the porosity and flexural properties of carbon fiber composites. The results showed that the carbon fiber composite had the minimum porosity and the best flexural properties when the extra pressure was 0.3 MPa.…”