Cure kinetics and autoclave-pressure dependence on physical and mechanical properties of woven carbon/epoxy 8552S/AS4 composite laminates

The final mechanical properties of composite laminates are highly dependent on their curing cycles in the autoclave. During this cycle, the temperature, pressure, vacuum, and treatment time will influence the quality of manufactured parts. The void content is considered the most harmful defects in carbon/epoxy laminates since they weaken the matrix-dominated mechanical properties such as interlaminar shear and compressive strengths. In the present work, differential scanning calorimetry is used to characterize the influence of time/temperature on the behavior of the epoxy resin. Then, a series of [0/90/−45/+45]s laminates composites are autoclave-cured under various applied pressures to evaluate their impact on microstructure and mechanical properties. The interlaminar shear modulus, interlaminar shear strength, laminate compressive modulus, and laminate compressive strength at room and operating engine temperature were measured. The correlation between microstructure and mechanical properties was also studied. The mechanical properties of manufactured carbon/epoxy laminates are found to be dependent on pressure and microstructure. These results are explored to establish an optimal autoclave pressure route that would minimize porosity without counterbalancing mechanical properties.