FEB 2016


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FEBRUARY 2016 10 CompositesWorld DESIGN & TESTING led to successful validation of the Trace theory and associated development methodology (see "Learn More"). To prove the benefts of this new theory, CompoSIDE conducted a series of studies benchmarking the Trace-based design approach to CFRP composites and compared the results with those obtained from standard FE modeling, using CompoSIDE's FESpace modeling capabilities. Flat and curved composite panels with diferent laminate confgurations were designed. More than 25 design options were investigated, including single-skin and sandwich designs. Material Trace Value, Universal Laminate Factor Charts (see "Learn More") and simple scaling functions were used to fnd alternative designs and to quantify weight savings compared to a baseline panel. Te outcome of this benchmark was very promising. Te results from trace-based scaling for both curved and fat panels correlated well with the FE results. Te discrepancy in most cases was less than 3.5%. Engineers were quite impressed with how efciently they could evaluate alternative options. Having solved one boundary problem for reference design, an engineer is able to replace either the material or even the entire laminate without rerunning additional FE modeling. Using scaling with the material trace and laminate factors would yield a good answer in most cases, especially in an early design phase. Tis could save a lot of time in design feasibility and trade studies. ยป Te development of composite parts and products is gener- ally characterized by extensive design and testing requirements when compared to plastic or metal equivalents. Composite materials and related engineering activities are regarded as inher- ently complex. It is generally true that these activities require advanced knowledge, tools and experience that, sometimes, are inaccessible. Yet there is strong market demand for high-strength and lightweight composite components, leading to continuous research and development activities to meet growing demand and overcome developmental barriers. Designers have to deal with these complexities, which include multiple variables, anisotropic properties and ply-based material architecture. And the complexity goes to the next level when it comes to processing and manufacturing. Most of today's composites industry works with thick plies layered in composite laminates. Tis practice presents a lot of tough challenges in manufacturing and design activities. Ply stacking sequence management and complex parts manufac- turability could be mentioned, among others. A lot of structural design challenges, such as delamination, coupling and shape distortions, resin-driven failures, local stress concentration, etc., are also inherited from laminate architecture. Tere are a lot of eforts in the industry to address these limitations and fnd better solutions. Our contention is that the real solution could be found in simplifcation and that the industry has to look at the problem diferently. In 2015, I teamed with Professor Research Emeritus of Stanford University Dr. Stephen Tsai to evaluate and apply his Trace approach into CompoSIDE's (Cowes, Isle of Wight, UK) composite design and analysis platform. Trace is, in essence, a simple invariant of tensorial transformation in matrix algebra and is a fundamental parameter for composite materials. Te research revealed that stifness and strength data for all modern carbon fber/polymer composite laminates converge to almost iden- tical values if normalized by their respective stifness trace. Tis universal stifness means that a master ply and simple scaling by means of material trace can be used to dimension laminate parts, just like they can for homogeneous materials. (Master ply is trace- normalized material which is shared for CFRP materials and the trace of this material is equal to 1. See "Learn More," p. 12). Tis is a truly powerful discovery. Following a call for a pilot project in 2014, Tsai and Compo- SIDE held collaborations with textile manufacturer Chomarat (Le Cheylard, France), which resulted in the practical development and commercialization of the latter's trademarked C-Ply carbon composite reinforcements, which feature thin plies, of-axis angles and non-crimp fber (NCF) material, resulting in stronger, lighter and homogeneous composite structures. Tis frst project Changing the design game with Trace FIG. 1 Inverting the testing pyramid This graph shows traditional and Trace-based testing strength pyramids. By adopting a trace and master ply material model, the cost of testing CFRP materials and structural components can be greatly reduced. Signifcantly reduced numbers of coupons can be tested. Only basic uniaxial testing is required to characterize any CFRP material, using stifness and strength invariants, which makes a testing program much more afordable and very similar to testing of metals. Additionally, Trace can help in quality assurance processes, enabling test personnel to quantify variations attributable to material quality or the manufacturing process by testing components. Source | CompoSIDE Ltd. Traditional Test Pyramid for Composites Trace-Based Test Pyramid for Composites Hundred of coupons, and tests Need one universal ply data from Uniaxial test [0] for each CFRP DETAILS ELEMENTS COUPONS COUPONS COMPOSITES COMPONENTS As Designed As Built (with defects) [0]

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