In this study, the effect of fiber orientation on the temperature history during the layup process is comprehensively investigated experimentally and numerically. Specimens with three different fiber orientations (i.e. [0°/0°/0°], [0°/45°/0°], and [0°/90°/0°]) are manufactured at two layup speeds and characterized for determining the degree of intimate contact and then calculating the thermal contact resistance. Then, an improved thermal model with thermal contact resistance is developed and validated to predict the temperature history accurately. The experimental results indicate that the degree of intimate contact decreases by increasing the difference in fiber orientation between the interfaces of successive plies, revealing a relationship between substrate fiber orientations and cooling rates. The effect of cooling rate on the degree of crystallinity is studied for all stacking configurations at two layup speeds and found that as the angle between the subsequent plies decreases, the cooling increases, leading to a drop in the degree of crystallinity. The outcomes of this study address the need for an improved thermal model approach for accurately predicting the thermal history of the manufactured composite by the laser-assisted fiber placement process.

Improving the quality of fiber-reinforced composite laminates using out-of-autoclave techniques has been a challenge for a long time. The recent trends toward the replacement of autoclave processes with out-of-autoclave processes for thermoplastic composites still lack a compressive recipe. This study first develops an understanding of the integrated effect of the automated fiber placement (AFP) lay-up process parameters (compaction force and lay-up velocity) and the type of post-processing: i) autoclave and ii) vacuum bag only (VBO) processing with two vacuum hold times, 2 and 24 h. The void content results highlight the potential of the VBO process to replace the autoclave with an improved void content of VBO with 24 vacuum hold times. Then, this result has been correlated with the morphology of voids after the AFP lay-up as isolated or connected via air permeability characterization. This study reveals that the high air permeability to effective porosity ratio of samples after AFP lay-up which is achievable with low compaction force facilitates the air removal mechanism during the VBO process with sufficient vacuum hold times.