Ultimate Strength Study of Structural Bionic CFRP-Sinker Bolt Assemblies Subjected to Preload under Three-Point...

Area of Science:

• Materials Science
• Mechanical Engineering
• Composite Materials

Background:

• Countersunk head bolted joints are essential for joining carbon fiber-reinforced plastics (CFRP).
• Understanding failure modes and damage evolution in these joints under bending load is crucial for structural integrity.
• The unique adaptability of tardigrades inspired a novel approach to studying material behavior.

Purpose of the Study:

• To investigate the failure mechanisms and damage progression in CFRP countersunk bolted joints subjected to bending loads.
• To develop and validate a 3D finite element model for predicting failure in these assemblies.
• To analyze the influence of bolt preload on stress distribution and ultimate load capacity.

Main Methods:

• Development of a 3D finite element failure prediction model for CFRP countersunk bolted assemblies, utilizing the Hashin failure criterion.
• Benchmarking the finite element analysis (FEA) model against experimental data to ensure accuracy.
• Parametric studies were conducted to examine stress distribution and the effect of bolt preload on bending limit load.

Main Results:

• FEA simulation results showed good correlation with experimental findings, accurately reflecting three-point bending failure and fracture.
• Stress distribution around the countersunk hole was found to be dependent on the laminate direction.
• Increasing bolt preload reduced initial damage load but an appropriate preload increased the ultimate load capacity.

Conclusions:

• The validated FEA model effectively predicts the failure behavior of CFRP countersunk bolted joints under bending.
• Bolt preload significantly influences the load-bearing capacity and failure initiation of CFRP joints.
• Optimizing bolt preload is a key strategy for enhancing the performance and durability of CFRP bolted structures.