Open hole tensile testing of 3D printed continuous carbon fiber reinforced composites

Abstract

In this study, the effects of stress concentration on the tensile properties of a 3D printed carbon fiber-nylon composite were investigated. The samples were 3D printed with continuous carbon fiber and chopped fiber reinforced nylon. Samples were manufactured with four different open hole sizes as 3. 175 mm (⅛ in), 6.35 mm (¼ in), 9.25 mm (⅜ in), and 12.7 mm (½ in). Five samples were manufactured for each hole size group. Continuous carbon fibers were printed in the longitudinal direction. Additional reinforcements were placed around the periphery of the open hole. Samples were tested under uniaxial tension. The results were compared with the prediction of fracture mechanics theories namely Average and Point Stress Criteria. The results show that failure was initiated at the stress concentration region but the progression into the hole was prevented with the presence of continuous fiber. The experimental findings show that the samples with larger holes are more sensitive to discontinuity than the ones with smaller holes. The results confirm that 3D printing can be used to strengthen the parts at the discontinuity region to mitigate the effect of stress concentration.

FDM-Based 3D Printing of Polymer and Associated Composite: A Review on Mechanical Properties, Defects and Treatments

“…The attraction towards the natural fibres such as flax, jute, basalt, bamboo and hemp are also increasing due to their eco friendliness and sustainability [ 137 , 138 , 139 , 140 , 141 , 142 ]. Most of the experiments have been performed with carbon fibre (CF) due to its excellent mechanical properties, lower density, corrosion, wear and moisture resistance, good thermal conductivity and electrical properties, low thermal expansion and piezoresistive behaviour, which is a special feature inherited from CF [ 143 , 144 , 145 , 146 , 147 , 148 ]. Hence, composites printed using CF as the reinforcement with matrix materials such as PEEK, PC, PE and PA are widely used in developing industrial applications, especially in the aerospace and automotive industries [ 149 ].…”

“… ( a ) Short CF immersed in Nylon matrix (onyx filament) [ 148 ]. ( b ) The orientation of the printed tensile specimens [ 152 ].…”

3D-Printed Carbon Fiber Reinforced Polymer Composites: A Systematic Review

“…(a) Analyzing the impact of process parameters on the mechanical behavior of specimens to optimize a certain property or group of properties [4][5][6][7][8][9]; (b) Analyzing the modes of failure to better understand the microstructural failure mechanisms of 3D printed fiber reinforced specimens [1,10,11]; The review is organized as follows. The following part of this section discusses the 3DP process of fiber reinforced composites based on a classification according to the type of fiber, matrix, 3D printer and process specifications.…”

Evaluating the effect of variable fiber content on mechanical properties of additively manufactured continuous carbon fiber composites

“…8,13,[16][17][18][19] Flexibility of 3D printing allows to direct the fiber in the desired direction to optimize the mechanical properties of interest. 20,21 Sanei et al 21 printed continuous carbon fiber around the periphery of open hole specimen to mitigate the effect of stress concentration. They observed that failure progression into the hole was blocked by the concentric fibers around the open hole.…”

“…20,21 Sanei et al. 21 printed continuous carbon fiber around the periphery of open hole specimen to mitigate the effect of stress concentration. They observed that failure progression into the hole was blocked by the concentric fibers around the open hole.…”