Static Residual Tensile Strength Response of GFRP Composite Laminates Subjected to Low-Velocity Impact

Jong-Il Kim,Yong-Hak Huh,Yong-Hwan Kim

doi:10.3390/app10165480

Abstract

The dependency of the static residual tensile strength for the Glass Fiber-Reinforced Plastic (GFRP) laminates after impact on the impact energy level and indent shape is investigated. In this study, two different laminates, unidirectional, [0°2]s) and TRI (tri-axial, (±45°/0°)2]s), were prepared using the vacuum infusion method, and an impact indent on the respective laminates was created at different energy levels with pyramidal and hemispherical impactors. Impact damage patterns, such as matrix cracking, delamination, debonding and fiber breakage, could be observed on the GFRP laminates by a scanning electron microscope (SEM), and it is found that those were dependent on the impactor head shape and laminate structure. Residual in-plane tensile strength of the impacted laminates was measured and the reduction of the strength is found to be dependent upon the impact damage patterns. Furthermore, in this study, stress concentrations in the vicinity of the indents were determined from full-field stress distribution obtained by three-dimensional Digital Image Correlation (3D DIC) measurement. It was found that the stress concentration was associated with the reduction of the residual strength for the GFRP laminates.

Highlights

IntroductionIt has been revealed that composite structures are considerably sensitive to damage caused by accidental impact events, especially those of a low velocity, during fabrication and in service [1], and the damage may not be easy to inspect visually or with Non-Destructive Evaluation (NDE) use.in order to apply the composite laminates in the structures reliably and cost-effectively, it may be important to understand the impact response of the laminates.The complex nature and anisotropic properties of the polymeric composites can lead to the formation of various types of damage, which may be associated with failure in complex patterns.Under the low-velocity impact loading, damage patterns, including delamination, matrix cracking, debonding, and fiber breakage, which are similar to common damage modes in composite laminates, occur, and the damage is significantly dependent on the impact energy levels and impactor shapes [2,3,4,5,6].The consequences of the damage may greatly reduce the stiffness and residual strength of the laminates.Mechanical performance of the impacted composite laminates could be characterized through inspecting the damage by nondestructive techniques such as ultrasonic C-scan, X-radiography and infrared thermography
Under the low-velocity impact loading, damage patterns, including delamination, matrix cracking, debonding, and fiber breakage, which are similar to common damage modes in composite laminates, occur, and the damage is significantly dependent on the impact energy levels and impactor shapes [2,3,4,5,6]
Two different indent shapes were introduced in the respective TRI and UD Glass Fiber-Reinforced Polymer (GFRP)

Summary

Introduction

It has been revealed that composite structures are considerably sensitive to damage caused by accidental impact events, especially those of a low velocity, during fabrication and in service [1], and the damage may not be easy to inspect visually or with Non-Destructive Evaluation (NDE) use.in order to apply the composite laminates in the structures reliably and cost-effectively, it may be important to understand the impact response of the laminates.The complex nature and anisotropic properties of the polymeric composites can lead to the formation of various types of damage, which may be associated with failure in complex patterns.Under the low-velocity impact loading, damage patterns, including delamination, matrix cracking, debonding, and fiber breakage, which are similar to common damage modes in composite laminates, occur, and the damage is significantly dependent on the impact energy levels and impactor shapes [2,3,4,5,6].The consequences of the damage may greatly reduce the stiffness and residual strength of the laminates.Mechanical performance of the impacted composite laminates could be characterized through inspecting the damage by nondestructive techniques such as ultrasonic C-scan, X-radiography and infrared thermography. It has been revealed that composite structures are considerably sensitive to damage caused by accidental impact events, especially those of a low velocity, during fabrication and in service [1], and the damage may not be easy to inspect visually or with Non-Destructive Evaluation (NDE) use. Under the low-velocity impact loading, damage patterns, including delamination, matrix cracking, debonding, and fiber breakage, which are similar to common damage modes in composite laminates, occur, and the damage is significantly dependent on the impact energy levels and impactor shapes [2,3,4,5,6]. Mechanical performance of the impacted composite laminates could be characterized through inspecting the damage by nondestructive techniques such as ultrasonic C-scan, X-radiography and infrared thermography. The threshold of barely visible impact damage in the laminates was investigated with the ND techniques [7], and Tuo et al [8,9] assessed the low-velocity impact damage induced at four

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Conclusion