Continuous lattice fabrication of ultra-lightweight composite structures

This paper introduces continuous lattice fabrication (CLF) - a novel additive manufacturing (AM) technique invented for fiber-reinforced thermoplastic composites - and demonstrates its ability to exploit anisotropic material properties in digitally fabricated structures. In contrast to the layer-by-layer approaches employed in most AM processes, CLF enables the directed orientation of the fibers in all spatial coordinates, that is in the x-, y-, and z-directions. Based on a serial pultrusion and extrusion approach, CLF consolidates commingled yarns in situ and allows for the continuous deposition of high fiber volume fraction (>50%) materials along a programmable trajectory without the use of molds or sacrificial layers by exploiting the high viscosities of fiber-filled polymer melts. The capacity of CLF to produce high-performance structural components is demonstrated in the fabrication of an ultra-lightweight load-bearing lattice structure with outstanding stiffness-to-density and strength-to-density performance (compression modulus of 13.23 MPa and compressive strength of 0.20 MPa at a core density of 9 mg/cm(3)). This digital fabrication method enables new approaches in load-tailored design, including the possibility to build freeform structures, which have previously been overlooked due to difficulties and limitations in modern fiber composite manufacturing capabilities. (C) 2017 Elsevier B.V. All rights reserved.