Face Damage Growth of Sandwich Composites under Compressive Loading: Experiments, Analytical and Finite Element...

Area of Science:

• Materials Science
• Mechanical Engineering
• Aerospace Engineering

Background:

• Composite sandwich panels are crucial in aerospace and automotive industries.
• Barely Visible Impact Damage (BVID) significantly degrades structural integrity.
• Understanding BVID effects under compression is vital for safety and performance.

Purpose of the Study:

• To analyze the failure mechanisms of composite sandwich panels with BVID under edge compression.
• To investigate the influence of fiber orientation on delamination propagation (Mode-I vs. Mode-II).
• To develop and validate analytical and numerical models for predicting failure strength and local buckling.

Main Methods:

• Edge compression tests on sandwich panels with a specific [(±45C)2,(0C,0G)4,(±45C)2] stacking sequence and induced BVID.
• Ultrasonic C-Scan and cross-section visual analysis to characterize impact damage morphology.
• Digital Image Correlation (DIC) for real-time delamination evolution monitoring.
• Development of an analytical model for Mode-I delamination and an FE model for local buckling prediction.

Main Results:

• Two distinct failure behaviors were observed based on fiber orientation relative to the load.
• Transverse fiber orientation led to Mode-I (opening) delamination propagation.
• Parallel fiber orientation resulted in Mode-II (shear) delamination propagation.
• Local buckling of the composite face was identified as the primary failure phenomenon preceding static strength.
• Experimental measurements of static load for local buckling and failure were obtained.

Conclusions:

• Fiber orientation critically dictates the delamination mode and failure behavior in BVID composite sandwich panels under compression.
• The developed analytical and FE models accurately predict the static strength and local buckling failure modes, correlating well with experimental data.
• This research provides valuable insights for designing damage-tolerant composite structures.