Influence of voids on interlaminar shear strength of carbon/epoxy fabric laminates

The effects of voids(void content,void shape and size)on the interlaminar shear strength of[(±45)_(4)/(0,90)/(±45)_(2)]_(S) and [(±45)/0_(4)/(0,90)/0_(2)]_(S) composite laminates were investigated.Specimens with void contents in the range of 0.2%-8.0%for [(±45)_(4)/(0,90)/(±45)_(2)]_(S) and 0.2%-6.1%for[(±45)/0_(4)/(0,90)/0_(2)]_(S) were fabricated from carbon/epoxy fabric through varying autoclave pressures.The characteristics of the voids were studied by using optical image analysis to explain the interlaminar shear strength results.The influences of voids on the interlaminar shear strength of the two stacking sequences were compared in terms of the void content and size and shape of the void.The effect of voids on the initiation and propagation of interlaminar failure of both stacking sequence composites was found.

Experimental investigation of vibration pretreatment-microwave curing process for carbon fiber reinforced resin matrix composites

The vibration pretreatment-microwave curing process is an efficient,low energy consumption,and high-quality out-of-autoclave curing process for carbon fiber resin matrix composites.This study aims to investigate the impact of vibration pretreatment temperature on the fiber weight content,microscopic morphology and mechanical properties of the composite laminates by using optical digital microscopy,universal tensile testing machine and thermo-gravimetric analyzer.Additionally,the combined mode of Bragg fiber grating sensor and temperature measurement fiber was employed to explore the effect of vibration pretreatment on the strain process during microwave curing.The study results revealed that the change in vibration pretreatment temperature had a slight impact on the fiber weight content when the vibration acceleration remained constant.The metallographic and interlaminar strength of the specimen formed at a vibration pretreatment temperature of 80℃ demonstrated a porosity of 0.414% and a 10.69% decrease in interlaminar shear strength compared to autoclave curing.Moreover,the introduction of the vibration energy field during the microwave curing process led to a significant reduction in residual strain in both the 0°and 90°fiber directions,when the laminate was cooled to 60℃.

Corrosion damage evolution and mechanical properties of carbon fiber reinforced aluminum laminate

Fiber metal laminates(FMLs),a kind of lightweight material with excellent comprehensive performance,have been successfully applied in aerospace.FMLs reinforced with carbon fiber have better mechanical properties than those with glass or aramid fiber.However,carbon fiber binding metal may lead to galvanic corrosion which limits its application.In this paper,electrochemical methods,optical microscope and scanning electron microscope were used to analyze the corrosion evolution of carbon fiber reinforced aluminum laminate(CARALL)in corrosive environment and explore anti-corrosion ways to protect CARALL.The results show that the connection between carbon fiber and aluminum alloy changes electric potential,causing galvanic corrosion.The galvanic corrosion will obviously accelerate CARALL corroded in solution,leading to a 72.1%decrease in interlaminar shear strength,and the crevice corrosion has a greater impact on CARALL resulting in delamination.The reduction of interlaminar shear strength has a similar linear relationship with the corrosion time.In addition,the adhesive layers between carbon fiber and aluminum alloy cannot protect CARALL,while side edge protection can effectively slow down corrosion rate.Therefore,the exposed edges should be coated with anti-corrosion painting.CARALL has the potential to be used for aerospace components.

Effects of electrochemical oxidation on surface and mechanical properties of dry-jet wet spun carbon fibers

The surface of dry-jet wet spun carbon fibers(CFs)is relatively smooth compared with those of wet spun CFs,which results in weak interfacial interactions between the fiber and the polymer resin.A surface functionalization treatment is particularly important to unleash the full potential of the superior mechanical properties of dry-jet wet spun CFs.In this study,the effects of electrochemical oxidation treatment time and current density on the surface structures and the mechanical properties of dry-jet wet spun CFs were investigated.The interlaminar shear strength of the CFs improves significantly from 69 to 84 MPa after 120 s of treatment.Further structural analysis reveals that the improvements are due to the addition of oxygen-containing functional groups and the optimization of the morphology on the surface of the CFs.

Hybrid Polymer Membrane Functionalized PBO Fibers/Cyanate Esters Wave‑Transparent Laminated Composites

Hybrid polymer membrane(TA-APTES),synthesized by tannic acid(TA)and aminopropyl trethoxysilane(APTES)based on the Schif’s base and Michael addition reaction,is deposited on the surface of poly(p-phenylene-2,6-benzobisoxazole)(PBO)fbers,and then grafted with epoxy-terminated polysesquisiloxane(POSS)to obtain POSS-g-PBO@TA-APTES fbers.The POSS-g-PBO@TA-APTES fbers reinforced bisphenol A dicyanate ester(BADCy)resins(POSS-g-PBO@TAAPTES fbers/BADCy)wave-transparent laminated composites are prepared.The interlaminar shear strength and fexural strength of POSS-g-PBO@TA-APTES fbers/BADCy composites are respectively enhanced from 36.7 and 587.4 MPa to 42.8 and 645.8 MPa,increased by 16.6%and 9.9%compared with those of PBO fbers/BADCy composites.At 1 MHz,the corresponding dielectric constant and dielectric loss are reduced to 2.85 and 0.0047,respectively,lower than those of PBO fbers/BADCy(3.06 and 0.006)composites.Meanwhile,the simulated wave transmittance rate of POSS-g-PBO@TA-APTES fbers/BADCy composites with the thicknesses of 1.5–3.5 mm is higher than 86.2%at 0.3–40 GHz.The volume resistivity and breakdown strength of POSS-g-PBO@TA-APTES fbers/BADCy composites are 2.8×10^(15)Ω·cm and 19.80 kV/mm,higher than PBO fbers/BADCy composites(2.2×10^(15)Ω·cm and 17.69 kV/mm),respectively.And the corresponding heat resistant index is 221.5℃,lower than PBO fbers/BADCy composites(229.6℃).