1. Objective 1 Objective 2 Objective 3 Conclusion Objectives
Design of a Fiberglass Skateboard
Auteur(e)s : Damien SOMMER Encadrement : Dr. Anastasios P. Vassilopoulos / Prof. Jean-François MOLINARI 2
Master 2015
1 Composite Construction Laboratory (CCLAB) EPFL / 2 Computational Solid Mechanics Laboratory (LSMS), EPFL
Objectives
Produce skateboard decks made of 100% of composite materials, with the same properties as a traditional skateboard.
Identify a parameter that could characterize the quality of a skateboard: a physical quantity that changes between an intact and a damaged board.
Create a finite element model that can predict the behaviour of a fiberglass skateboard.
Objective 1
Objective 2
Objective 3
Step 1: Choose what materials to use.
Strong unidirectional glass fibers (UD)
Light mat fibers
Step 1: Determine the initial static and dynamic properties of the boards.
Step 1: Import the geometry of a skate to Gmsh (meshing software).
List the main points defining the ¼ of geometry of a skate and apply symmetries.
3-points bending testing to get the initial stiffness k [N/mm] of the manufactured boards.
Step 2: Obtain the design of the cross section of the skate.
Classical Lamination Theory (CLT) to determine how to stack UD and mat fibers.
Step 2: Create a mesh for the simulation.
Creation of a structured mesh to control the computational time.
Dynamic testing with accelerometer to get the eigenfrequency and dumping ratio.
Step 3: Simulate 3-points bending for a fiberglass skateboard.
Obtain elastic constants of UD and mat fibers theoretically and experimentally.
Set boundary conditions.
Write a script simulating 3-points bending with the library Akantu.
Step 3: Manufacture of skateboard decks.
Manufacture by hand lay-up technique and vacuum bag moulding.
Step 2: Damage the boards.
Controlled high energy impacts inflicted by a drop load tower.
Step 3: Repeat step 1 and 2 to obtain the static and dynamic properties of damaged boards.
Compare the results of eigenfrequency, dumping ratio and stiffness before and after the damages.
Step 4: Finalize the shape of the boards.
Rotatory drilling and hand trimming.
Step 4: Compare the results of the FEM simulation with the CLT and with the 3-points bending tests realised in lab.
Get displacement, stress and strain profiles along significative axis.
Step 5: Prepare the boards for static and dynamic testing ► Objective 2.
Conclusion
The experimental tests showed that the stiffness and eigenfrequency decrease proportionally to the level of damages inflicted to the board.
Step 5’: Set up a pair of trucks and wheels and skate it !
The manufacture process of fiberglass skateboard has been elaborated and permits the creation of boards of similar characteristics (stiffness, weight, geometry, etc…).
The FEM can simulate the behaviour of any stacking sequences of isotropic/orthotropic fibers, but needs to be calibrated with other experimental material data.