Research on Low-Velocity Impact Response of Novel Short-Fiber-Reinforced Composite Laminates

Abstract

Short-fiber-reinforced polymers (SFRPs) based on unidirectionally arrayed chopped strands (UACSs) have excellent formability and outstanding mechanical response. The low-velocity impact response, such as the delamination, damage tolerance and energy absorption of UACS composites, are essential to guarantee the stability and safety of composite components in service. The current study investigates the low-velocity impact response of continuous carbon-fiber-reinforced polymer (CFRP) and UACS laminates with vertical slits under drop-weight impact with various impact energies (4, 7 and 11 J). The in-plane size of the studied samples is 100 mm × 100 mm, and the stacking sequence is [0/90]4s. The time–history curves of load and energy are examined during low-velocity impact experiments, as well as the nonvisible damages are obtained by ultrasound C-scan imaging technique. A user-defined subroutine VUMAT, including the Johnson–Cook material and failure model, which is used to simulate the elastic–plastic property of the slits filled with resin, is coded in ABAQUS/Explicit. According to C-scan inspections of the impact-damaged laminates, UACS specimens show more severe delamination as impact energy increases. The damaged area of continuous CFRP laminates under impact energy of 11 J is 311 mm2, while that of UACS laminates is 1230 mm2. The slits have a negative effect on the load-bearing capacity but increase the energy absorption of UACS laminates by approximately 80% compared to the continuous CFRP laminates at 7 J. According to the variables of different damage modes in numerical simulation, cracks appear at the slits and then expand along the direction perpendicular to the slits, leading to the fracture of fiber. Nevertheless, as the damage expands to the slits, the delamination confines the damage propagation. The existence of slits could guide the path of damage propagation.

Effect of slit size on low‐velocity impact behavior of composite laminates with regularly arrayed chopped strands: Experimental and numerical analysis

“…UACS laminates with two different slit sizes were prepared for LVI experiments to compare their impact performance with that of UACS laminates with 25 mm slits that had been tested. 36 The structure diagram of UACS laminates with vertical slit sizes of 5, 10, and 25 mm, respectively, is illustrated in Figure 1. All the specimens were prepared with a stacking sequence of [0/90] 4s and a 2 mm thickness.…”

“…Regular vertical slits were introduced in unidirectional CFRP prepreg utilizing a numerical control cutting machine. UACS laminates with two different slit sizes were prepared for LVI experiments to compare their impact performance with that of UACS laminates with 25 mm slits that had been tested 36 . The structure diagram of UACS laminates with vertical slit sizes of 5, 10, and 25 mm, respectively, is illustrated in Figure 1.…”

Simulation and Experiment on the Low-Velocity Impact Response of Flax Fabric Reinforced Composites

“…In order to precisely simulate the impact damage of woven fabric reinforced composites, Wu et al [26] developed yarn-level finite element models of hybrid 3D carbon/glass woven orthogonal composites, including failure criteria and progressive damage behavior. Huang et al [27] simulated the effect of slits filled with resin on the impact properties of unidirectionally arrayed chopped carbon fiber reinforced composites by using the Johnson-Cook material and failure model to describe the elastic-plastic property of the slits in the finite element models and found that the slits had a negative effect on the load-bearing capacity but increased the energy absorption. The aforementioned research shows that finite element modeling is an effective way to simulate and analyze the damage mechanism of woven fabric reinforced composites under low-velocity impact by introducing accurate failure criteria and progressive damage behavior and building an appropriate geometric model.…”