| Firstly, In this paper, E-51/DDS/BMI systems was modified using different contents of BMI, and the heat resistance, mechanical properties and microstructure of the bending sections of E-51/DDS/BMI composites were studied by DSC, DMA, TGA, SEM and mechanical property test.Secondly, BMI/DBA/Nano-Si O2/DDS/E-51 composite systems were toughened and modificated by using nano silicon dioxide(Nano-Si O2). The 4,4’-diaminodiphenylsufone(DDS) was used as curing agent. The effects of different Nano-Si O2 content on the thermal and mechanical properties of BMI/DBA/Nano-Si O2/DDS/E-51 composite systems were studied by means of differential scanning calorimetry(DSC), dynamic mechanical thermal analyzer(DMA), thermal gravimetric analysis(TGA) and mechanical property test. The results showed that, adding a certain amount of nano-Si O2 can improve mechanical strength and heat resistance of the composite systems of BMI/DBA/Nano-Si O2/DDS/E-51, when the mass fraction of nano-Si O2 was 2%, E-51/BMI/DDS/ nano-Si O2 composite had better mechanical property and its tensile strength, flexural strength and notched impact strength were improved by 24.1%, 25.4% and 83.8%, respectively, compared to the E-51/BMI/DDS composites. Simultaneously, when the content of nano-Si O2 is 2%, E-51/BMI/DDS/nano-Si O2 composite had good heat resistance, and the initial thermal decomposition temperature and the maximum thermal decomposition temperature were 375.53℃, 401.79℃, respectively. In addition, the fracture surface micro-morphology of BMI/DBA/Nano-Si O2/DDS/E-51 composite were characterized by scanning electron microscope(SEM), the analytic results showed that the fracture surface of BMI/DBA/nano-Si O2/DDS/E-51 composite system was rougher than BMI/DBA/DDS/E-51 composite without nano-Si O2. With the increase of nano-Si O2, composite bending fracture roughness increased, which suggested that due to the addition of nano-Si O2, the propagation path of micro-cracks was changed, and the micro-crack propagation was more difficult. Therefore, the existence of nano-Si O2 particles may interfere with direction of micro-crack propagation, thus changing the path of propagation of micro-cracks, so nano-Si O2 particles added to the composites improved their flexural strength.Finally, with short cut carbon fiber, E-51/BMI/DBA/DDS/CF composites were prepared, and the influence of carbon fiber(CF) contents on mechanical and thermal properties of composites prepared, i.e., DSC, TGA, DMA and mechanical property test of the samples cured were studied. The results showed that, when content of the short carbon fiber was 0.25wt%, the mechanical properties of the E-51/BMI/DBA/DDS/CF composites increased maximum, and the tensile strength, flexural strength, flexural modulus and impact toughness were increased by 48.52%, 32.15%, 25.77% and 150.91%, respectively, compared to E-51/BMI/DBA/DDS composite without short carbon fiber. In addition, morphology of bending sections of the composites was analyzed by SEM, which found that when content of the carbon fibers was lower than 0.25wt%, the carbon fibers were well dispersed in the resin matrix. In the process of composites subjected to external load, with micro crack propagation growth, if encountering carbon fibers, the propagation direction will be changed. Simultaneously, the bridging effect also prevented crack growth, thereby increasing the flexural strength of the composites. The number of river stripe increased, the distance between the stripes reduced, and the surface roughness increased, which implied, with addition of carbon fibers into composites, micro-crack propagation path was changed, so that the propagation and growth of microcracks became more difficult. When content of the short carbon fibers increased from 0.25wt% to 0.35wt%, agglomeration of short carbon fibers was observed. Therefore, when content of the short carbon fibers was higher than 0.25wt%, the flexural strength began to gradually decline. |
PDF Full Text Request