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The structural properties of braided composite laminates are significantly affected by the low‐velocity impact (LVI). In this paper, the impact resistance and damage tolerance of triaxial braid structure laminates at different positions were mainly studied. Three hybrid biaxial (B)/triaxial (T) braided composite structures of BBTT, BTTB, and TTBB were designed, and LVI test and post‐impact compression tests were carried out. The results show that the triaxial braided fabric with quasi‐isotropic on the impact side caused more significant matrix cracks along the axis yarn direction, and the matrix damage area and delamination area were larger. For triaxial braided ply with high curl levels, severe fiber fracture and relatively concentrated damage occurred first on the non‐impact side. Interestingly, triaxial braided fabrics exhibited better impact resistance in terms of mechanical response when distributed across the specimen surface. However, a global damage pattern appears at high energy levels, which seriously reduced the residual strength of the structure and showed the worst damage tolerance. The damage quantification analysis of cracks, dent depths, delamination and residual compressive strength caused by the LVI of hybrid shaft number braided laminates was carried out in this work, which provided a valuable reference for engineering failure analysis and rational structure optimization of composite laminates. [ABSTRACT FROM AUTHOR]

• The transverse impact response of hybrid biaxial/uniaxial braided tube was studied. • The effects of architecture hybridization and stacking sequence were identified. • Proposed FE model provided accurate predication of the impact behaviors. Tubular composites in automobile engineering are susceptible to transverse loading events. This paper deals with transverse low-velocity impacts on interply hybrid tubes made of biaxial/uniaxial braided fabric layers. For comparison, drop weight tests were performed on hybrid tubes with biaxial braided surface layers and uniaxial braided inner layer (BUB), with contrary stacking sequence (UBU), pure biaxial and uniaxial braided tubes (BBB and UUU). Numerical models were established to predict the impact behaviors and evaluate the hybrid effects. X-ray micro-computed tomography (Micro-CT) was also employed to identity the cracking location and characterize the damage mechanism. The results showed that the impact response of braided tube was related to its structural deformation resistance, which was determined by properties of reinforced layers varying with different stacking sequence. The hybrid effect became more obvious at higher impact energy. At impact energy of 15.4 J, hybrid tube (BUB) yielded the highest impact resistance with small structural deformation. The biaxial braided layer protected the specimen surface by constraining intralaminar crack propagation through the interlacing patterns. Meanwhile, it promoted crack tip propagating to the subsequent uniaxial braided layer and transferred the impact load. Thus, the material involvement of the inner layer was improved, which was responsible for providing a higher in-plane tensile property due to its low yarn crimp. [ABSTRACT FROM AUTHOR]

• Advantages of asymmetric hybridization on impact resistance and resilience. • Rules of external damage area and internal crack volume distribution. • Damage mechanism of carbon/Kevlar hybridization laminates. The ply structure has a significant effect on the impact resistance and failure behavior of composite laminates. In this paper, carbon/Kevlar hybrid fabric reinforcements were prepared with different Kevlar ratio (0%, 25%, 50%, 75%, 100%) by replacing carbon fabric plies on the non-impact side by Kevlar plies. The low-velocity impact tests for all configurations were carried out under 15 J and 25 J energy respectively. The results show that the maximum deflection, impact duration, impact absorption energy and absorption energy efficiency of hybrid laminates increased with the Kevlar hybrid ratio, whereas the peak force presented a decreasing trend, which indicates that the adding of Kevlar layer makes the laminates more ductile than non-hybrid carbon structure. The damage mechanism of the carbon fiber ply was brittle fiber fracture, resin cracking and resin shedding, while the fibers pull-out and tows splitting was found in Kevlar ply. The critical structural damages start from the non-impact side and evolve to the impact side. And the rules of internal crack volume distribution with Kevlar plies are consistent with the trend of external damage area on the non-impact side. It is suggested that in order to take into account the peak strength and excellent structural resilience, Kevlar asymmetric-hybrid ratio of 25% is the most appropriate. The reason is that an appropriate small ratio of Kevlar cushion ply can not only effectively avoid the tensile fracture at non-impact side happened in the non-hybrid carbon structure, but also withstand enough impact load by maintaining a high carbon fiber content. [ABSTRACT FROM AUTHOR]