Effect of embedded periodic fiber placement gap defects on the microstructure and bistable behavior of thermoplastic composite laminates.

By inducing periodic gaps, conventional automated fiber placement avoids overlap defects, which are generally prohibited in composite component manufacturing. However, bistable laminates are highly sensitive to imperfections, and it is critical to explore the effect of periodic gaps on the performance of bistable laminates. The principal curvatures and load–displacement curves of thermoplastic composite laminates with manually embedded periodic gaps was studied using experimental and numerical methods in this paper. SEM microscopy was used to observe the gap areas of the cross section of laminates to assess the microstructure of gaps with width variations after curing. In addition, a numerical method was proposed based on the experimentally determined evolution of gap widths and thicknesses of laminate. Subsequently, the effects of gap width, single‐layer thickness, and total thickness on the principal curvature were investigated. Gaps embedded in the 0° and 90° layers of bistable laminates demonstrated a substantial decrease in the snap load of the laminates. Interestingly, by embedding different gap widths in the 0° layers of the laminates, the snap load discrepancy between the snap‐through and snap‐back processes increased as the gap width widened, and the same trend was also found in the curvatures in the two stable states. Highlights: Bistable characteristics of laminates with periodic gap defects.Utilizing gaps embedding in 0° layer to tailor the mechanical properties. [ABSTRACT FROM AUTHOR]