# Repeated Impact Performance of Carbon Spread-Tow Woven Stitched Composite with Anti-Sandwich Structure

## TL;DR

This paper studies a new composite material with an anti-sandwich structure that shows strong resistance to repeated impacts, suitable for aerospace applications.

## Contribution

The novel anti-sandwich composite structure with STW core and hybrid surface layers is introduced for enhanced impact resistance.

## Key findings

- Increasing core layer thickness improves impact resistance stiffness.
- NW felt in surface layers enhances energy absorption but reduces stiffness.
- The composite with 2:1 core-to-surface thickness ratio achieved a peak impact load of 17.43 kN.

## Abstract

Spread-tow woven fabrics (STWs) have attracted considerable attention owing to their thin-layered characteristics, high fiber strength utilization rate and superior designability, finding wide application in the aerospace field. To meet the application requirements for materials with high specific strength/specific modulus in the aerospace field, this study designed an anti-sandwich structured composite with high specific load-bearing capacity. Herein, the core layer was a load-bearing structure composed of STW, while the surface layers were hybrid lightweight structures made of STW and nonwoven (NW) felt. Repeated impact test results showed that increasing the thickness ratio of the core layer enhanced the impact resistant stiffness of the overall structure, whereas increasing the proportion of NW felt in the surface layers improved the energy absorption of the composites but reduced their load-bearing stiffness and strength. The composite exhibited superior repeated impact resistance, achieving a peak impact load of 17.43 kN when the thickness ratio of the core layer to the surface layers was 2:1 and the hybrid ratio of the surface layers was 3:1. No penetration occurred after 20 repeated impacts at the 50 J or 3 repeated impacts at 100 J. Meanwhile, both the maximum displacement and impact duration increased, whereas the bending stiffness declined as the number of impacts increased. The failure mode was mainly characterized by progressive interfacial cracking in the surface layers and fracture in the core layer.