Low-velocity impact behavior of carbon-Kevlar fiber intraply hybrid composites

An important issue that fiber-reinforced composites face in applications is their sensitivity to low-velocity impact. Low-velocity impact not only causes material penetration and perforation but also introduces internal damage in the forms of delamination, matrix cracking, and fiber breakage. This reduces the damage tolerance of fiber-reinforced composites, posing a potential threat to their protective performance. The research objective of this paper is to enhance the impact resistance through fiber hybridization and to explore the influence of the fabric structure on the impact resistance of carbon-Kevlar fiber intraply hybrid composites.

In this study, carbon-Kevlar fiber intraply hybrid composites with different fabric structures were fabricated using the vacuum assisted resin infusion (VARI) process. Through low-velocity impact tests using a drop hammer under 30- and 60-J energy, the reinforcement effect of intraply hybridization on the composites and the influence of the fabric structures on the mechanical properties and impact resistance of carbon-Kevlar fiber intraply hybrid composites were investigated. Low-velocity impact was simulated through an impact simulation model of hybrid fiber composites, and the damage mechanism of the specimens under impact loads was explored. The impact response behaviors and impact resistance of each specimen were comparatively analyzed using the load - displacement, load - time, and energy - time curves.

Results show that: (1) At an energy of 30 J, the specimen with the maximum peak load is the plain warp carbon weft Kevlar (P-CC/KK) specimen, reaching 3.30 kN, which is 72.77% and 106.25% higher than the maximum peak loads of plain carbon (P-C) and twill warp carbon weft Kevlar (T-CC/KK) specimens (with the minimum peak load), respectively. At an energy of 60 J, the specimen with the maximum peak load is also P-CC/KK, reaching 3.68 kN, which is 97.85% higher than the maximum peak load of the P-C specimen (with the minimum peak load). (2) Comparing the maximum deflection of rebounded specimens, the T-CC/KK specimen has the largest deflection at 30- and 60-J energy, reaching 24.74 and 31.92 mm, respectively. (3) From the energy absorption curve, the energy absorption of the hybrid specimens is significantly increased compared with that of P-C. At an energy of 30 J, the plain carbon-Kevlar alternate (P-CK/CK) specimen just stops the impactor, absorbing the most energy of 29.54 J, which is 132% higher than the energy absorbed by P-C. At an energy of 60 J, the T-CC/KK specimen absorbs the most energy of 59.65 J, which is 324% higher than the energy absorbed by P-C, suffering greater bending deformation and internal damage. (4) The low-velocity impact simulation study based on the finite element model on the P-CC/KK specimens shows that the load - time and load - displacement curves from the tests and simulation results have a high degree of consistency, and errors in the peak loads of the curves and maximum deflections of the specimens are less than 10%.

The low-velocity impact resistance of the carbon-Kevlar hybrid composites is significantly improved compared to that of pure carbon fiber. The energy absorption of the hybrid specimens is greatly enhanced compared to that of P-C. During impact, P-CC/KK has the highest peak load and T-CC/KK has the largest deflection. The warp carbon weft Kevlar (CC/KK) structure has better impact resistance than the carbon-Kevlar alternate (CK/CK) structure, and the plain weave structure has superior low-velocity impact resistance compared to the twill weave structure. The established finite element model has relatively high accuracy, and the numerical simulation model well reflects the in-plane damage of the composites under the nonpenetration condition.