Performance of Hybrid Reinforced Composite Substrates in Adhesively Bonded Joints Under Varied Loading Rates.

Area of Science:

• Materials Science
• Mechanical Engineering
• Composite Materials

Background:

• Adhesive bonding is preferred for joining composites due to superior performance over traditional methods.
• Delamination is a critical failure mode in adhesively bonded composite joints, leading to premature failure.
• Enhancing through-thickness strength of composite substrates is key to mitigating delamination risks.

Purpose of the Study:

• To investigate substrate reinforcement techniques for preventing delamination in carbon fiber reinforced polymer (CFRP) single-lap joints (SLJs).
• To evaluate the impact of incorporating aluminum and polymer layers on joint failure load and mode under various loading rates.
• To numerically predict failure mechanisms using cohesive zone modeling (CZM).

Main Methods:

• Investigated reinforcement of CFRP substrates using aluminum and film adhesive layers (25% of substrate thickness).
• Tested bonded joints under quasi-static (1 mm/min), high-rate (0.1 m/s), and impact (2.5 m/s) loading conditions.
• Employed cohesive zone modeling (CZM) for numerical simulation of failure loads and mechanisms.

Main Results:

• Under impact loading, aluminum and polymer reinforcement significantly increased failure load and energy absorption.
• Aluminum-reinforced samples showed a 39% higher failure load and 15% greater energy dissipation than reference CFRP.
• Polymer reinforcement offered enhanced specific strength with minimal weight increase, suitable for aerospace.

Conclusions:

• Reinforcing CFRP SLJs with outer layers of aluminum or polymer effectively prevents delamination and enhances performance.
• Aluminum reinforcement provides substantial improvements in failure load and energy absorption, especially under impact.
• Polymer reinforcement presents a lightweight solution for improving specific strength in aerospace composite joints.