Experimental Investigation of Impactor Diameter Effect on Low-Velocity Impact Response of CFRP Laminates in a Drop-Weight Impact Event.

Hongyi Cao,Aiqin Tian,Lei Zhang,Mingshun Jiang,Lin Sun,Mengyuan Ma,Jianying Liang,Lei Jia

doi:10.3390/ma13184131

Abstract

The present study delved into the effect of impactor diameter on low velocity impact response and damage characteristics of CFRP. Moreover, the phased array ultrasonic technique (PAUT) was adopted to identify the impact damages based on double-sided scanning. Low-velocity impact tests were carried out using three hemispherical impactors with different diameters. The relationship of impact response and impactor diameters was analyzed by ultrasonic C-scans and S-scans, combined with impact response parameters. Subsequently, the damage characteristics were assessed in terms of dent depth, delamination area and extension shape via the thickness, and the relationships between absorbed energy, impactor displacement, dent depth and delamination area were elucidated. As revealed from experiment results, double-sided PAUT is capable of representing the internal damage characteristics more accurately. Moreover, the impactor diameter slightly affects the impact response under small impact energy, whereas it significantly affects the impact response under large impact energy.

Highlights

Carbon fiber reinforced polymer (CFRP) has been extensively employed in lightweight design(e.g., aerospace, automotive and rail traffic) for its merits of high specific strength and stiffness.CFRP is susceptible to damage caused by out-of-plane impact force, which is one of the major concerns in the design of structures made of CFRPs [1,2]
Damage response behavior of composites under impact remains unclear for the multitude of CFRPs that can be synthesized by a variety of stacking sequence and manufacturing procedures
Nondestructive testing (NDT) is considered a critical testing method to detect and characterize internal damages in CFRPs, which has been employed in different stages of the life of Materials 2020, 13, 4131; doi:10.3390/ma13184131

Summary

Introduction

CFRP is susceptible to damage caused by out-of-plane impact force, which is one of the major concerns in the design of structures made of CFRPs [1,2]. Its vulnerability to low velocity impact events will induce Barely Visible Impact Damages (BVID) in the composite structures, which is manifested mostly by delamination and matrix crack with limited fiber breakage [3,4,5] that cannot be detected macroscopically. BVIDs pose significant safety issues since they are capable of generating extended damage and decreasing the residual strength and durability of the structure, which may cause catastrophic failure [6,7,8]. Impact damages of CFRP refer to a sophisticated mechanism that consists of matrix cracking, delamination and fiber breakage. Nondestructive testing (NDT) is considered a critical testing method to detect and characterize internal damages in CFRPs, which has been employed in different stages of the life of Materials 2020, 13, 4131; doi:10.3390/ma13184131 www.mdpi.com/journal/materials

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Conclusion