Study On Properties Of 3-D Braided UHMWPE Fiber/Carbon Fiber Hybrid Composites

3-D braided composites have high flexural strength and impact toughness and fatigue life and damage tolerance, and they are promising biomedical materials for high-load applications. As a new polymer fiber with high performance, UHMWPE fiber which exhibits very low friction coefficient, high wear resistance and high impact strength is widely used in biomedical applications. So study on the 3-D braided composites using as biomedical materials is of academic and practical significance.3-D braided UHMWPE fiber reinforced epoxy resin composites (UH3D/ER) were prepared by resin transfer molding (RTM) process. At the same time, carbon fiber and UHMWPE fiber were used to produce the 3-D braided hybrid composites (3-D UH/CF/ER) in order to improve weak compressive and creep properties of the UH3D/ER composites, and their mechanical, moisture absorption, friction and wear and fatigue properties were studies in this paper.The results show that, with the increase of the CF/UHMWPE fiber hybrid ratio, the flexural and longitudinal compressive performance of the 3-D UH/CF/ER composites improves, and their longitudinal shear strength and impact toughness decrease. The fracture mechanism of the 3-D UH/CF/ER hybrid composites is determined by the properties of the two fibers and their hybrid ratio. The fiber dispersion, distributing mode, hybrid ratio and load model have obvious effects on the hybrid effect coefficient of the 3-D UH/CF/ER hybrid composites, and the computation values of the transverse and longitudinal shear strength of the hybrid composites through hybrid effect coefficient have good coherence with the experimental values.Under the relative humidity of 75%,the moisture absorption rate of CF and UHMWPE fiber is about zero and 0.35%, respectively, while that of KF exceeds 5%. Compared with epoxy resin, the moisture absorption velocity and rate of the UH3D/ER and UHL/ER composites in 37℃distilled water are higher. Fiber surface treatment can effectively reduce the moisture absorption velocity and rate of the UH3D/ER composites. The moisture absorption dynamics curves of the 3-D UH/CF/ER hybrid composites in 37℃distilled water distribute between those of the UH3D/ER and CF3D/ER composites, and all of these curves show similar two-stage characteristics, viz. the first stage is typical Fick's diffusion, and the moisture absorption rate and the square root of time still satisfy linear relation in the second stage, while the curves in this stage can not be described with Fick's law. The two-stage mathematics model is successfully used to forecast the moisture absorption behaviors of the UH3D/ER and 3-D UH/CF/ER hybrid composites in this paper.At the sliding velocity of 0.42 m/s and the normal load of 100 N, the friction coefficient and wear rate of the UH3D/ER composites decrease with the improvement of fiber volume fraction, and adhesive wear and light abrasive wear occur in thissituation. The friction coefficient of the CF3D/ER composites is higher than that of the UH3D/ER and KF3D/ER composites, while the wear rate of the CF3D/ER composites is lowest among the three materials. Similar to the UH3D/ER composites, adhesion wear occurs on the surface of the KF3D/ER composites, while abrasive wear appears on the CF3D/ER composites surface. With the same total fiber volume fraction, the friction coefficient of the 3-D UH/CF/ER hybrid composites increases and their wear rate decreases with the increase of the CF/UHMWPE fiber hybrid ration. The wear mechanism of the hybrid composites intensively depends on the CF/UHMWPE fiber hybrid ration. Abrasive wear is dominant when the hybrid ratio is high, and contrarily adhesion wear is leading. The mixture load distributing mode is used to forecast the friction coefficient of the UH3D/ER composites, and the result shows that the computation value equals to the experimental one whenθ=0.74 (p<0.05), while this mode is not fit for the 3-D UH/CF/ER hybrid composites.Under the same experimental condition (0.4σo, 105 times), the fatigue performance of the CF3D/ER composites is better than that of the UH3D/ER and KF3D/ER composites. The flexural fatigue damage forms of 3-D braided composites mainly are these types as follows: (a) crack extension in the fiber bundles/resin matrix interface, (b) fiber/matrix interface fracture, (c) resin matrix rupture, (d) fiber fracture and so on. Among these damage forms, the crack extension in the fiber bundles/resin matrix interface is the uppermost, and this is obvious difference between the 3-D and unidirectional composites. Moisture absorption will lead to the decrease of the fatigue tolerance of the UH3D/ER composites. The fatigue life of the UH3D/ER composites under the flexural load of 0.4σo is 5×106 times, and it reduces to 8×104 times under 0.5σo.The hybrid effect coefficient the 3-D UH/CF/ER hybrid composites and friction coefficient and fatigue life of the UH3D/ER composites were successively forecasted in this paper. This is significant to reduce study period and cost of the 3-D braided and hybrid composites.