Study On The Damaged Interface Healing Of PBO Fiber Composites Based On Photothermal Effects

In fiber reinforced composites,"interface"is the interface region between fiber and resin matrix,which is considered to be the key factor to determine the overall properties of composite materials.However,during the long-term use of composite materials,the interface is easily affected by mechanical force,chemical,thermal and ultraviolet radiation,resulting in cracks or microcracks,which eventually leads to the the failure of overall performance of composite materials.Because these cracks exist in the deep of composite structure,it is difficult to detect and heal them.To prolong the service life of composite materials,it has been a hot research topic for researchers to endow composite interface damage healing performance.This paper focus on the problem that it is difficult to detect the interface damage and accurately heal multiple times of thermoplastic resin matrix composites.Taking PBO fiber as the research object,the construction and mechanism of PBO fiber composite interface damage healing based on photo-thermal effect are studied.BN-PDA-PBO fibers with photo-thermal interface photo-thermal conversion properties are prepared by the method of coating.By adjusting the impregnation time and mass concentration of PBO fibers in boron nitride-polydopamine（BN-PDA）nanosheets solution,BN-PDA nanosheets are uniformly and densely loaded on the surface of PBO fibers.The TPU-BN-PDA-PBO monofilament composite is prepared with polyurethane（TPU）as resin matrix and BN-PDA-PBO fiber as reinforcement.Monofilament pull-out test is used to evaluate the photo-thermal repair performance of PBO monofilament composites.The results show that the photo-thermal healing efficiency of TPU-BN-PDA-PBO monofilament composite is 72.72% under Xe light irradiation,and the photo-thermal healing efficiency can still be maintained at 70% after five repair cycles.In contrast,PBO monofilament composites without BN-PDA nanosheets have no interface damage healing.The reason is that BN-PDA nanosheets in the interface layer can absorb light energy and convert it into heat energy,which make the interface temperature of TPU-BN-PDA-PBO monofilament composite increases.When the interface temperature reaches above T_gof resin matrix,the molecular chain of the resin matrix moves to heal the interface damage.Due to the coupling of Cu₂S and Ag nanoparticles can lead to the enhancement of local surface plasmon resonance effect of nanoparticles under illumination,so Cu₂S-Ag nanoparticles have a strong synergistic photo-thermal conversion ability.By optimizing the concentration of silver nitrate,the concentration of cuprous sulfide seed solution,the mass concentration of PBO fiber and the reaction time,Cu₂S-Ag-PDA nanoparticles are loaded on the surface of PBO fiber compactly and evenly.The obtained Cu₂S-Ag-PDA-PBO fiber exhibit the surface photothermal conversion performance.At the same time,TPU-Cu₂S-Ag-PDA-PBO monofilament composite is prepared by using polyurethane as resin matrix and Cu₂S-Ag-PDA-PBO fiber as reinforcement.The results show that Cu₂S-Ag-PDA nanoparticles can efficiently absorb light energy and convert it into heat energy under Xe light irradiation,which leads to in-situ heating of the resin matrix at the interface damage of TPU-Cu₂S-Ag-PDA-PBO monofilament composite,eventually realizing the interface damage healing.The computational results show that the interface shear strength healing efficiency of TPU-Cu₂S-Ag-PDA-PBO monofilament composite can reach 80.97%,which is higher than that of TPU-BN-PDA-PBO monofilament composite.Simultaneously,the healing efficiency of TPU-Cu₂S-Ag-PDA-PBO monofilament composite can be maintained at 75%-81% within 5 cycles.The PBO fiber composite is prepared by molding with the BN-PDA-PBO,Cu₂S-Ag-PDA-PBO and PBO@NH₂-MIL-88B-Fe-GO fiber fabric as reinforcement and polyurethane as resin matrix.The loading effect of Cu₂S-Ag-PDA,BN-PDA,NH₂-MIL-88B-Fe-GO on the surface of PBO fiber fabric is controlled by optimizing reaction time,mass concentration of photothermal conversion reagent and PBO fiber.Three-point bending test is used to evaluate the photothermal healing performance of PBO molded fiber composites.The results show that the bending strength photo-thermalhealingefficiencyoftheTPU-BN-PDA-PBO,TPU-Cu₂S-Ag-PDA-PBO,TPU-PBO@NH₂-MIL-88B-Fe-GO molded fiber composites is 55.2%,64.9%and 67.1%,respectively,which is much higher than that of TPU-PBO fiber composite.The interface damage healing strategy of PBO fiber composites based on photo-thermal effect proposed in this paper is not only limited to PBO fiber composites,but also has a wide application prospect in other material repair fields.