Experimental Study of Repeated Low‐Velocity Impact Damage and Residual Compressive Strength of Double‐Double Laminates

ABSTRACT Double‐Double (DD) laminates, with a stacking sequence of [±Φ/±Ψ] rT , show strong potential for reducing structural weight while enhancing mechanical performance. However, their behavior under repeated low‐velocity impacts (LVI), which is crucial for long‐term structural reliability, remains insufficiently understood. In this study, stiffness‐equivalent DD and legacy quad laminates (LQL) were experimentally evaluated through repeated single‐point impact tests at three energy levels (10, 15, and 30 J), followed by compression‐after‐impact (CAI) testing. Internal delamination was characterized using ultrasonic C‐scanning. The DD laminates exhibited a 15.59%–36.80% higher peak impact force, a 32.21%–44.12% smaller delamination projection area (DDPA), and a 2.95%–15.99% higher residual compressive strength (RCS) compared with the LQL. These results demonstrate that DD laminates can sustain higher impact loads, delay delamination propagation, and retain greater post‐impact strength, highlighting their superior resistance to repeated impacts and potential for application in lightweight composite structures.