Thermoplastic Mandrel for Manufacturing Composite Components with Complex Structure

Abstract

This study was to solve the mandrel demolding problem after curing the composite component with complex structure. In this paper, a reusable thermoplastic mandrel with heating softening characteristics was developed by resin transfer molding (RTM). The glass transition temperature (Tg), surface roughness, and reusability of the mandrel, as well as the shape, surface roughness, thickness uniformity, and internal quality of the formed structure, were tested. The result showed that the Tg of the mandrel was between 80 and 90 °C and the surface roughness was less than Ra 0.5 μm. Additionally, the mandrel can be recycled and can still maintain a good shape after 20 times of deformation. By using this method, the demolding process can be realized by heating and softening the mandrel. The profile error of the formed structure was within 0.5 mm, the surface roughness was less than Ra 0.5 μm, the thickness error was within 0.2 mm, and the average porosity of the upper and lower halves of composite parts was 0.72% and 0.61%. All those data showed that the formed part was in good shape and of good quality. The thermoplastic mandrel can solve the demolding problem of composite materials with complex shapes.

Variable Shape Tooling for Composite Manufacturing: A Systematic Review

“…One study (7%) investigates a cyanate-ester-based SMP [23]. Two studies (13%) focus on blends of thermoplastic resins based on PMMA with an epoxy-based thermoset [16,50]. Two studies (13%) investigate thermoplastics: PMMA (7%) [51] and PP, PA6, and PBT (7%) [43].…”

“…Everhart et al (2006) [23] and Koury (2005) [44] (13%) used high-strain fiber reinforcement not specified elsewhere, which allow for elongations of up to 150%. Jing et al (2021) [50,51] and Lu et al [16] (20%) used carbon fiber fabric reinforcement. Since they only utilized the softening-by-heating effect, no elongation of the polymer was required.…”

“…However, the process enables the production of fiber-reinforced mandrels without dry spots and voids. Jing et al ( 2021) used RTM to manufacture their carbon fiber fabricreinforced thermoplastic/thermoset-blend mandrel [50,51]. Pfledderer et al [45] used vacuum-assisted RTM for manufacturing their high-strain fiber-reinforced mandrel.…”

“…All studies except [43] (93%) focus on reusable mandrels, which can be reformed for each production cycle. On the other hand, only in [46] and [50] (13%), the durability of the tooling regarding cycles is investigated. In [46] (7%), "the mandrels with diameter deformation ratios 25%, 50%, 75% and 100% could undergo 100, 38, 15 cycles and only one cycle before fail."…”

“…In [46] (7%), "the mandrels with diameter deformation ratios 25%, 50%, 75% and 100% could undergo 100, 38, 15 cycles and only one cycle before fail." In [50] (7%), 20 cycles were possible. Miadowitz (2019) [43] (7%) investigated single-use blow-molded mandrels, which are shredded after demolding and re-feed to the extruder.…”