Study on the Forming Quality of Carbon Fiber Composite Braided-punched Preforms
The braided-punched composite forming technology can achieve the integrated forming of large thickness rotary-shaped composite preforms.To investigate the forming quality of braided-punched composite mate-rial preforms with different yarn K-numbers and braiding angles,as well as woven-punched performs as a control group,were experimentally produced.The morphology of the backside punched fiber bundles and the damage to the base fabric were considered,and the preform fiber bundles elongation χf was proposed to quantitatively charac-terize the punched fiber bundle morphology.By combining the actual changes in the peeling curve of the punched preforms,the average values of all peaks and troughs within the effective peeling curve were used to describe the interlaminar peeling force.The results show that when the yarn K-number is 6K,the average elongation of the brai-ded-punched preforms is increased by 7.2%compared to the woven-punched preforms,making the fiber bun-dle morphology of the braided-punched preforms more ideal.When the yarn K-number increases from 6 to 12,the average elongation of the fiber bundles on the back of the woven-punched preforms increases by 78.9%.In com-parison,that of the braided-punched preforms decreases by 30.6%due to the yarn being displaced at the punching site,increasing the fiber bundle's projected area.The braided-punched preforms show significant ad-vantages in interlaminar peeling force,with each sample showing an increase of over 38.0%compared to the wov-en-punched preforms.The interlaminar peeling strength of the 12K yarn braided-punched preforms is 78.3%greater than that of the 6K yarn.As the braiding angle increases from 30° to 60°,the average peeling strength of the braided-punched preforms decreases by 46.6%.
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