Investigation of the mechanical and ballistic properties of hybrid carbon/aramid woven laminates

High-performance ballistic fibers,such as aramid fiber and ultra-high-molecular-weight polyethylene(UHMWPE),are commonly used in anti-ballistic structures due to their low density,high tensile strength and high specific modulus.However,their low modulus in the thickness direction and insufficient shear strength limits their application in certain ballistic structure.In contrast,carbon fiber reinforced epoxy resin matrix composites(CFRP)have the characteristics of high modulus in the thickness direction and high shear resistance.However,carbon fibers are rarely used and applied for protection purposes.A hybridization with aramid fiber reinforced epoxy resin matrix composites(AFRP)and CFRP has the potential to improve the stiffness and the ballistic property of the typical ballistic fiber composites.The hybrid effects on the flexural property and ballistic performance of the hybrid CFRP/AFRP laminates were investigated.Through conducting mechanical property tests and ballistic tests,two sets of reliable simulation parameters for AFRP and CFRP were established using LS-DYNA software,respectively.The experimental results suggested that by increasing the content of CFRP that the flexural properties of hybrid CFRP/AFRP laminates were enhanced.The ballistic tests'results and the simulation illustrated that the specific energy absorption by the perforation method of CFRP achieved 77.7%of AFRP.When CFRP was on the striking face,the shear resistance of the laminates and the resistance force to the projectiles was promoted at the initial penetration stage.The proportion of fiber tensile failures in the AFRP layers was also enhanced with the addition of CFRP during the penetration process.These improvements resulted in the ballistic performance of hybrid CFRP/AFRP laminates was better than AFRP when the CFRP content was 20 wt%and 30 wt%.

Microstructural evolution,tensile property and dynamic compressive property of FSWed Ti-6Al-4V alloy

Friction stir welding was applied to Ti-6 A1-4 V plates with 5 mm in thickness.The microstructure and mechanical properties were investigated.A full lamellar microstructure was developed near the top surface,and the size of priorβgrain gradually decreases as the distance from the top surface increases.The microstructure of the bottom is fine equiaxed a grains,and the mean size is2μm.A mixture microstructure consisting of primary a,lamellarα+βand fine equiaxedαis discovered in thermomechanically affected zone(TMAZ).Results of transverse tensile test show that the tensile strength of the joint reaches 98%that of the base material(BM).Quasi-static compression test shows that the joint exhibits larger compressive strength and failure strain than the BM.Dynamic compressive strength of the joint is close to that of the BM;furthermore,the strain at the peak stress and energy absorption of the joint are larger than those of the BM.