Part 1 of this article, published in the March/April 2015 issue of Reinforced Plastics, presented an insight into multiaxial reinforcements specialist FORMAX's approach to materials characterization, simulation of processing and composites performance. In this concluding article, Liam O'Sullivan, KTP Associate and Composite Engineer at FORMAX, presents a case study of a typical automotive part and examines the benefits of this approach, including the development of optimized fabric architecture. This process involves the use of FORMAX's recently developed capabilities to measure drape and permeability characteristics of reinforcement fabrics, which have been developed as part of a two-year Knowledge Transfer Partnership (KTP) with the University of Nottingham and Innovate UK.
Evaluating the structural integrity of a laminate lay-up
The laminate lay-up for the case study automotive floor was specified based on typical automotive laminate construction and consisted of quasi-isotropic full coverage layers, with a series of unidirectional layers along the tunnel caps to provide extra rigidity.
FORMAX partnered with Autodesk, a provider of 3D design and engineering software, to conduct a finite element (FE) analysis on the design to analyse the stresses and deflections in the floor under loading. The floor was subjected to torsional load up to failure. Analyses were conducted with standard mechanical properties and both a 10% increase and decrease in strength and modulus of the fabrics. The stress concentrations show that the fiber directions and geometry of the floor panel cause increased stresses at the top of the intersections between the tunnels, and thus laminate integrity at this point is critical. Any discontinuities in the fibers at this point, such as darting to avoid wrinkles, should be avoided if possible.
This article appeared in the Nov/Dec issue of Reinforced Plastics.