Study on the Quality of Quasi-Isotropic Composite Laminates Containing a Circular Hole

Venkateswaran Santhanakrishnan Balakrishnan,Tilo Schumann,Holger Seidlitz,Marcello Ambrosio

doi:10.5539/jmsr.v6n4p67

Venkateswaran Santhanakrishnan Balakrishnan, Tilo Schumann + Show 2 more

Open Access

https://doi.org/10.5539/jmsr.v6n4p67

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Abstract

Composite structures used in modern engineering applications are often subjected to circular holes in order to join with metal components via riveting, bolting or pinning joints. These design based holes will interrupt the force flux in the direction of the fibers and create high stress concentrations near the notched area. Objective of the project is to understand the quality of the quasi-isotropic composite laminates ([45°, -45°, 0°, 90°]S) containing circular hole. To achieve this objective, a 3-phase portal milling machine and a 5kW continuous wave (cw) CO2 laser system were used to produce the circular holes in the composite laminates. The processing parameters for both the processes are varied to understand its influence. The quality of the circular hole produced by these methods are further investigated and compared in order to arrive at the optimum processing parameters for the given quasi-isotropic composite laminates.The hole qualities were evaluated by means of delamination factor caused by milling; cone angle, matrix evaporation for cw-CO2 laser system. For further comparisons, the optimal parameter combinations of both methods were selected for a tensile test according to the standard ASTM D5766-2002.

Highlights

Fiber reinforced polymer (FRP) laminates have high stiffness and strength to weight ratio
Introduction of the hole by cw-CO2 lasers caused a reduction of maximum force by 27.94% compared to unnotched specimen and the drilling results in a reduction of 26.06%
The optimal method for introducing the circular hole was determined by means of maximum loadable tensile force

Summary

Introduction

Fiber reinforced polymer (FRP) laminates have high stiffness and strength to weight ratio. The commonly used mechanical joining method are riveting, bolting or pinning joints These design based holes will interrupt the flux of the force in the direction of the fibers and create high stress concentrations near the notched area. These high notch stress concentrations are often the possible regions for failure in structural parts (Awerbuch & Madhu, 1985). As a consequence, this weaken the FRP component significant and prevent the optimal exploitation of the high anisotropic lightweight potential of the composites (Seidlitz et al, 2014). Since there is an Increasing usage of FRP laminates in the design of structural parts with high mechanical performance, fatigue behavior of holed FRP laminates requires a better understanding (Kroll et al, 2017; Toubal, Karama, & Lorrain, 2005)

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