Experimental study on mechanical responses of 3D needle‐punched composite preforms at different needling densities: Failure structures, tensile and interlayer peeling strengths

In this study, needle‐punched quartz fiber felt / fabrics preforms (NQFFPs) with a wide needling densities (NDs) range from 70 to 280 punches/cm2 were manufactured, then the inner correlation among the NDs, mechanical properties and structural failure modes were studied and revealed. Firstly, the effects of NDs on mechanical strengths, which included tensile and interlayer peeling strengths of NQFFPs, were analyzed through experimental methods. Moreover, MATLAB software was applied to fit the NDs‐mechanical strength curves, then best fitting equations were defined to characterize the change rules between NDs and mechanical strengths. Additionally, with NDs increment, tensile strengths decreased from 0.727 to 0.0925 MPa, whereas interlayer peeling strengths increased from 83.46 to 135.04 N/m. Afterwards, the 3D image technology was utilized to capture failure morphologies of NQFFPs at different NDs from tensile and interlayer peeling experiments, which furtherly revealed the failure mechanisms of NQFFPs at different NDs. This work is significant for the engineering manufacturing and application of needle‐punched preforms and the composites. Highlights Failure structure characteristics of NQFFPs at different NDs were captured. Change rules between NDs and strengths were characterized by math equations. The correlation among NDs, fracture morphologies and strengths was revealed. Tensile and inter‐layer reponse analysis of 3D needle‐punched composite preforms.