Abstract
In this work, a new method of through-thickness reinforcement of composites has been developed which does not have a detrimental effect on the in-plane properties.
An initial study was undertaken to determine the best method for producing the
through thickness polymeric reinforcement. This involved placement of molten
polymeric strands and room temperature polymeric strands into a dry fabric preform to determine which was the best route. In the preferred method a blunted hypodermic needle was inserted through the dry fabric preform allowing a room temperature polymer coated carbon filament to be inserted through the needle. The needle was then withdrawn leaving the filament in place and the filament was then cut with approximately 5mm of the filament protruding from each side of the preform. This process was repeated for the remainder of the composite plaque to give the required pin density. The dry pinned preform was then pressed in a heated tool to bend the filaments over and press them into the fibres.
Thermoset epoxy resin was infused through the tool using the RTM method and cured to form the composite. Several plaques were produced for tensile, bearing and mode 1 tests. These were at a nominal volume fraction of ~47%.
No statistically significant reduction in the in-plane tensile properties was
observed between the pinned and unpinned laminate. Mode I delamination testing is ongoing, but preliminary testing has been positive, and it is expected that this method will significantly improve the interlaminar properties. Further work will investigate optimising the procedure, with potential to look at other filaments, pin densities and providing additional benefits such as through-thickness conductivity. Given the repetitive nature of the pinning, the potential for automation may also be investigated.
Recently a curved preform was produced using the technique; it offers excellent
preform stability with low bulk-factor.
An initial study was undertaken to determine the best method for producing the
through thickness polymeric reinforcement. This involved placement of molten
polymeric strands and room temperature polymeric strands into a dry fabric preform to determine which was the best route. In the preferred method a blunted hypodermic needle was inserted through the dry fabric preform allowing a room temperature polymer coated carbon filament to be inserted through the needle. The needle was then withdrawn leaving the filament in place and the filament was then cut with approximately 5mm of the filament protruding from each side of the preform. This process was repeated for the remainder of the composite plaque to give the required pin density. The dry pinned preform was then pressed in a heated tool to bend the filaments over and press them into the fibres.
Thermoset epoxy resin was infused through the tool using the RTM method and cured to form the composite. Several plaques were produced for tensile, bearing and mode 1 tests. These were at a nominal volume fraction of ~47%.
No statistically significant reduction in the in-plane tensile properties was
observed between the pinned and unpinned laminate. Mode I delamination testing is ongoing, but preliminary testing has been positive, and it is expected that this method will significantly improve the interlaminar properties. Further work will investigate optimising the procedure, with potential to look at other filaments, pin densities and providing additional benefits such as through-thickness conductivity. Given the repetitive nature of the pinning, the potential for automation may also be investigated.
Recently a curved preform was produced using the technique; it offers excellent
preform stability with low bulk-factor.
| Original language | English |
|---|---|
| Number of pages | 20 |
| Publication status | Published (in print/issue) - 3 Jan 2020 |
