The role of ply orientation on the resin flow under compaction in thermoplastic composites
Topic(s) : Manufacturing
Co-authors :
Alejandro JIMENEZ DEL TORO (NETHERLANDS), Julie TEUWEN (NETHERLANDS)Abstract :
The use of carbon fibre reinforced thermoplastic composites and their inherent in-situ consolidation (ISC) capabilities hold a large potential for automated manufacturing of composite parts. Within these manufacturing technologies, automated fibre placement (AFP) could deliver in-situ consolidated parts with high design flexibility and scrap minimisation, which would be attractive for numerous industries.
However, ISC can only be adequately achieved at placement speeds of a few tens of millimetres per second. As the placement speed is increased, only partial consolidation between the incoming tape and substrate is reached. This diminishes the mechanical properties at the interfaces, causing a drop in relevant mechanical and physico-chemical properties. Current research suggests that the limiting factor to achieve ISC at higher placement speeds is the lack of intimate contact due to the presence of dry areas at the surfaces of both, incoming tape and substrate. It also suggests that, to achieve full intimate contact, both squeeze and percolation resin flow are required. Squeeze flow refers to the resin flow within the tape's plane, i.e. longitudinal and transverse directions; and percolation flow refers to the through-thickness, normal to the tape's plane, resin flow.
Squeeze flow has been extensively studied in CFTP and models have been proposed. It is the most dominant resin flow in AFP and has a distinct anisotropy. It is favoured in the transverse fibre direction of the unidirectional tape, with the fibres and resin being displaced by the normal compression forces. Little to no resin flow occurs in the longitudinal direction, due to the large extensional viscosity that the resin experiences caused by the presence of the inextensible carbon fibres. Earlier studies suggest that a [0,90]n layup hinders transverse squeeze flow and promotes percolation flow under normal compression compared to a [0]n one. This would occur as unidirectional, inextensible fibres are present in both longitudinal and transverse direction, increasing the extensional viscosity and effectively hindering squeeze flow in the tape's plane.
These results suggest that the substrate might play a relevant role on promoting squeeze or percolation flow in AFP. Thus, further investigation on the role of the substrate on the development of ISC could lead to improved understanding of the compaction phase in AFP. On doing so, further AFP optimisation towards achieving ISC at higher placement speeds could be achieved.
Thus, this work studies the effect of the substrate’s ply orientation on the resin flow behaviour upon compaction. The material used is commercially available carbon fibre reinforced polyphenylene sulphide unidirectional tape. The compaction experiments are done in a dynamic-mechanical analyser, in which the tape's orientation, pressure and compaction time are varied. The characterisation involves optical microscopy and micro-CT scans of the compacted composites.
However, ISC can only be adequately achieved at placement speeds of a few tens of millimetres per second. As the placement speed is increased, only partial consolidation between the incoming tape and substrate is reached. This diminishes the mechanical properties at the interfaces, causing a drop in relevant mechanical and physico-chemical properties. Current research suggests that the limiting factor to achieve ISC at higher placement speeds is the lack of intimate contact due to the presence of dry areas at the surfaces of both, incoming tape and substrate. It also suggests that, to achieve full intimate contact, both squeeze and percolation resin flow are required. Squeeze flow refers to the resin flow within the tape's plane, i.e. longitudinal and transverse directions; and percolation flow refers to the through-thickness, normal to the tape's plane, resin flow.
Squeeze flow has been extensively studied in CFTP and models have been proposed. It is the most dominant resin flow in AFP and has a distinct anisotropy. It is favoured in the transverse fibre direction of the unidirectional tape, with the fibres and resin being displaced by the normal compression forces. Little to no resin flow occurs in the longitudinal direction, due to the large extensional viscosity that the resin experiences caused by the presence of the inextensible carbon fibres. Earlier studies suggest that a [0,90]n layup hinders transverse squeeze flow and promotes percolation flow under normal compression compared to a [0]n one. This would occur as unidirectional, inextensible fibres are present in both longitudinal and transverse direction, increasing the extensional viscosity and effectively hindering squeeze flow in the tape's plane.
These results suggest that the substrate might play a relevant role on promoting squeeze or percolation flow in AFP. Thus, further investigation on the role of the substrate on the development of ISC could lead to improved understanding of the compaction phase in AFP. On doing so, further AFP optimisation towards achieving ISC at higher placement speeds could be achieved.
Thus, this work studies the effect of the substrate’s ply orientation on the resin flow behaviour upon compaction. The material used is commercially available carbon fibre reinforced polyphenylene sulphide unidirectional tape. The compaction experiments are done in a dynamic-mechanical analyser, in which the tape's orientation, pressure and compaction time are varied. The characterisation involves optical microscopy and micro-CT scans of the compacted composites.