Industrial Robotics CFRP Structural Component

A large U-shaped composite structure, roughly 850 mm in depth and weighing 23 kg fully equipped, built to carry a robot end-effector and its associated tooling on an industrial robotics platform. The part was engineered as two bonded half-shells rather than a riveted assembly, keeping the structure lightweight, stiff, and free of stress-raising fastener holes.

Every bond line and every ply orientation was validated by nonlinear FEM under a full acceleration load case, and a dedicated draping guide was produced to control fibre orientation and ply placement zone-by-zone through manufacturing.

The component's laminate was built from paired-angle plies rather than a conventional 0/45/90/-45 quad stack, following a Double-Double laminate architecture: successive layers combined orientations such as [-60,60], [0,90], [45,-45], and [60,-60] within a compact six-layer global stack. This angle-pair approach gives finer control over in-plane and bending stiffness for a given laminate thickness, well suited to a part carrying combined bending, torsion, and dynamic robot-arm loads.

To avoid the stress concentrations and drilling operations that rivets would introduce, the component was designed as two half-shells bonded along a dedicated joint line running the full length of the part. Every bonded interface — between half-shells, between the outer woven skin and the structural laminate, and at the robot and tool-changer interfaces — was checked against an 11 MPa adhesive shear limit across three governing acceleration load cases (in-plane, out-of-plane, and rotational), with all results remaining within the adhesive's allowable.

A full nonlinear FEM model captured the assembly under these load cases, tracking both structural displacement and stress in the metallic robot-interface fittings. The first structural mode was found at 19 Hz, with the relative displacement between the two end-effector nozzles held below 0.33 mm under the governing out-of-plane acceleration case — a critical requirement for maintaining process accuracy at the tool tip.

Because ply orientation accuracy directly affects the laminate's stiffness and fatigue behaviour, a dedicated draping guide was produced alongside the FEM validation. It defined exact fibre orientation targets at multiple cross-sections around the part's curved and straight sections, and flagged where the as-draped geometry would exceed the mould's soyage (trim) boundary — giving the manufacturing team a clear, zone-by-zone reference for laying up each ply correctly.