Analysis of Impact Characteristics and Detection of Internal Defects for Unidirectional Carbon Composites with Respect to Fiber Orientation.

Sun-Ho Go,Alexandre Tugirumubano,Hong-Gun Kim

doi:10.3390/polym13020203

Abstract

With the increasing use of carbon fiber reinforced plastics in various fields, carbon fiber composites based on prepregs have attracted attention in industries and academia research. However, prepreg manufacturing processes are costly, and the strength of structures varies depending on the orientation and defects (pores and delamination). For the non-contact evaluation of internal defects, the lock-in infrared thermography was proposed to investigate the defects in the composites subjected to the compression after impact test (CAI). The drop-weight impact test was conducted to study the impact behavior of the composites according to fibers orientation for composite fabricated using unidirectional (UD) carbon fiber prepregs. Using CAI tests, the residual compressive strengths were determined, and the damage modes were detected using a thermal camera. The results of the drop weight impact tests showed that the specimen laminated at 0° suffered the largest damage because of susceptibility of the resin to impact. The specimens with 0°/90° and +45°/−45° fibers orientation exhibited more than 90% of the impact energy absorption and good impact resistance. Furthermore, the specimens that underwent the impact tests were subjected to compressive test simultaneously with the lock-in thermography defects detection. The results showed that internal delamination, fibers splitting, and broken fibers occurred. The temperature differences in the residual compression tests were not significant.

Highlights

In recent years, the research on composites materials and the industrial applications has rapidly expanded with the aim of decreasing the energy consumption and the development of new materials with lightweight characteristic
In the case of the specimen laminated with all fibers laminated in 0◦, the non-destructive inspection method was not conducted because the composite with all plies oriented in 0◦ was completely broken by the drop-weight impact test
The compression after impact test (CAI) test was not conducted on the specimen laminated at an angle of 0◦, as it was completely destroyed by the drop-weight impact test

Summary

Introduction

The research on composites materials and the industrial applications has rapidly expanded with the aim of decreasing the energy consumption and the development of new materials with lightweight characteristic. Carbon fiber-reinforced plastics (CFRPs) have been used in several industries that require weight reduction, due to their higher specific strength, higher specific stiffness, low density, their excellent chemical resistance, and electrical properties when compared with existing metallic materials [1,2,3]. The CFRPs are the composites where the carbon fibers are used as strengthening elements to provide high strength in polymer matrix. The common method of fabricating these composites is through laminating the dry carbon fibers fabrics and applying the polymer as binding element or laying up the carbon fibers fabrics pre-impregnated with resin (prepreg). The carbon fiber fabrics may be either unidirectional (UD) or woven. The properties of the CFRP depend on the lamination sequence, orientation of the fibers, and manufacturing methods

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