Selective Microwave Sintering for Preparation of Organic Fiber Network‐Reinforced Thermoplastic Composites

ABSTRACT High‐performance thermoplastic polymer‐matrix composites (PMCs) were critical materials in high‐end manufacturing. However, short fiber‐reinforced composites exhibited limited mechanical properties, while the processing of continuous fiber‐reinforced composites was rather complex. Herein, we proposed a selective microwave sintering strategy that enabled the in situ formation of a continuous UHMWPE fibers network modified with graphite and Fe 3 O 4 within polyamide 11 (PA11) composites. During microwave sintering, the modified short fibers absorbed microwaves and generated heat, resulting in interfacial sintering and bonding of the fibers to form a continuous network within the PA11 matrix. The bonding point density of fibers in the composite material reached 330 units/cm 3 . A notable notched impact strength of 45.8 kJ/m 2 was achieved in the UHMWPE fiber‐reinforced composite containing only 3 wt% graphite and 3 wt% Fe 3 O 4 after microwave treatment, representing a 154% enhancement compared to the PA11 matrix. Furthermore, when compared to untreated short‐fiber composites: the tensile strength of microwave‐treated PA11/UHMWPE@3Fe 3 O 4 3G composite was 51 MPa, a 79% increase over the untreated short fiber composite (28.5 MPa), while the flexural strength showed a 22.7% improvement, reaching 93.5 MPa. This was a new paradigm for designing high‐performance thermoplastic composites with promising potential for lightweight structural applications.