Composite Spool Case Study
CSS was tasked to design and develop a lightweight FRP composite spool for use in a performance sporting goods application.   The composite part had to match or exceed the incumbent machined aluminum spool performance, mate with existing hardware, and visually communicate a high end product story.
Composite Spool FEA Model
Designing a lightweight, low inertia structure capable of resisting deflection due to high out of plane flange loads and developing a cost-effective manufacturing approach in light of the spool's radical flange-body-flange cross section transitions were the main project challenges.
CSS conducted several design and manufacturing trade studies before settling on a Bladder Inflation Molded outer composite shell supported by an inner pultruded hollow composite core.
Braided carbon fiber biaxial sleeving was selected for the outer shell primary reinforcement.   The braid was sized to layup over the large diameter flange and neck down onto the small diameter body without reaching the braid's respective compression or tension jam states thereby maintaining flange to flange fiber continuity.   Die cut flexible core mat and carbon fiber fabric reinforcements added to the back face of each flange to create a lightweight sandwich construction with sufficient out of plane flange stiffness and strength.
Carbon Fiber Composite Spool Assemblies
CSS fabricated custom silicone bladders to support BIM molding of the carbon fiber composite outer shell. Near net-shape shell preforms were laid up over a bladder covered male layup form then packed into clamshell (female) aluminum tooling.   Vacuum was pulled between the aluminum tool and custom silicone bladder before infusing the preform with epoxy resin at elevated temperature.   Infused shells were demolded and trimmed to length prior to bonding a pultruded fiberglass tube length into the each shell using a quick set epoxy adhesive.
Several composite spool prototypes were fabricated and successfully tested under load at elevated temperature to demonstrate concept feasibility.   CSS' composite spool was 35% lighter than its aluminum counterpart and the continuous carbon fiber braid outer layer delivered the desired high end product story.