Composites simulation can accelerate acceptance

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Altair’s David Mason believes “reliable simulation technology will catalyze composites growth.”

Automakers are poised to unleash a new wave of lightweight, structurally robust composite materials that they believe will help them meet the new, ultra-stringent U.S. and European fuel-efficiency regulations. Carbon fiber, long proven in racecars and aircraft for its weight-saving and safety benefits, is moving into significantly higher volumes in production cars. David Mason, Vice President of Global Automotive for Altair Engineering, spoke with AEI Associate Editor Ryan Gehm about how modeling and FE analysis tools can help engineers optimize their structural composite designs.

Mason also will discuss the topic during a free webcast hosted by AEI on March 7 (register at www.sae.org/mags/aei/webcasts.htm) and again on April 16 at the SAE 2013 World Congress in Detroit as part of the “Structural Plastic Composite Components: The Multi-Material Vehicle Opportunity and Technology Gaps” technical session.

What role will modeling and FE analysis tools play in accelerating composites growth in the automotive sector?

Today the use of finite element simulation and CAE is an established part of the design process for all OEMs faced by the challenges of increasingly complex products and high cost for physical test verification. OEMs have developed successful simulation processes to meet complex crash, NVH, durability, vehicle dynamics, thermal, and aerodynamic requirements. CAE simulation is already widely used in parts made of common metal and engineered plastic materials (particulate composites with short, long fibers) and is now offered for the most advanced new composites (i.e., continuous carbon-fiber laminates). The availability of reliable simulation technology will catalyze composites growth, bringing confidence to design engineers and management already comfortable with what CAE delivers for traditional metal-based vehicles.

One of the biggest roadblocks facing composites is the challenge of their integration into the existing infrastructure serving the automotive sector. Infrastructure challenges span the entire product life cycle from joining processes in assembly plants, to paint lines, all the way to body repair shops. Ultimately, any future benefits coming from reduction in composites material cost or from more efficient manufacturing techniques may be less of a game-changer for growth if not paralleled with advancements in design technologies like CAE.

Can these design-engineering activities help to bring composites costs down to a level suitable for mainstream vehicles?

Composites, and in particular laminate composites, are today seen as costly alternatives to metals. In the attempt to bring down the cost of composites, it is essential to use CAE optimization to reduce material usage and design the part efficiently. Additionally, for carbon-fiber laminate composites, software optimization goes beyond material saving. Optimization is a comprehensive solution aimed at guiding and simplifying the design of laminate composite structures. The design flexibility offered by composites derives mostly from the ability to tailor the material itself to the loading requirements. Optimization is the best strategy in the hand of design engineers to choose the right selection of laminate ply thicknesses, orientations, and stacking. Unless an optimized-based design is followed, the results will be a composite part often overdesigned with redundant material, which adds cost and weight.

Additionally, the cost of an automotive component derives not just from the material itself but also from R&D, manufacturing, and assembly of the components that, particularly for smaller productions, may take a larger portion of the final cost. CAE-based design, among other things, allows [design engineers] to easily identify opportunities for part consolidation, which is one of the tactical advantages of plastic with respect to traditional metals systems often built by assembling multiple smaller parts with multiple connections.

Does Altair’s composites modeling suite focus on manufacturing aspects as well as product design?

Altair’s composites modeling suite is mainly tailored to the needs of composites design engineers, but it does so taking into account many of the constraints required by manufacturing. Design, manufacturing, and assembly requirements are concurrent aspects of solid engineering aimed at product simplification and cost saving. In laminate composite software optimization, for example, the CAE analyst may control the minimum and maximum total laminate thickness, the minimum and maximum ply thickness, the minimum and maximum percentage of a fiber orientation, enforce constant thickness for a particular ply orientation, [and] offer control for balancing and symmetry constraints, ply angle drops, max number of consecutive plies of same fiber orientation or other constraints, and various ply book rules enforced in manufacturing.

Moreover, Altair HyperWorks Partner Alliance also offers software such as Moldex, a leading injection-molding simulation solution that enables designers of plastic part and molds to create in-depth simulation with the widest application range of injection molding processes to optimize product design and manufacturability.

Where does composites modeling technology go from here? Any major challenges to be overcome?

Because of aerospace-dominant requirements, composites’ academic research, characterization, and CAE modeling technology have been mainly focused towards structures in the linear material behavior range (stiffness and fatigue) with margins of safety. The understanding of composites’ dynamic performance, energy absorption, and failure is not as detailed yet, particularly for parts with complex geometry. Most of the published studies on composites are based on simple geometry such as axis-symmetric tubes subject to quasi-static loads. For automotive, new fibers, matrix, and additives are being introduced into the market to improve the composites performance and reduce cost. This brings a major challenge to further penetration of composites in areas of the vehicle that affect the crash performance. More detailed work on material characterization and modeling is beginning to take place and is required.

How has Altair’s automotive composites design business benefited from its work for aerospace and/or defense?

The switch from aluminum-centric into composite-intensive airplanes has been a major undertaking for the aerospace industry and its suppliers. Altair in particular has invested significantly in new software technologies and broader knowledge on composites among developers and its 700+ engineers of Altair Product Design. Years of composite focus for aerospace, military, racing, and niche vehicle applications has nurtured new composites’ CAE modeling methods, new material models, material fittings techniques, failure modes, adhesive joining, optimization methods, and laminate-composite postprocessing. These are greats benefits that Altair now brings to its automotive customers.

Altair’s material-agnostic design approach also helps put the right material in the right place, taking advantage of the unique opportunities offered by composites in the most promising automotive applications.

What’s your personal outlook for the future of composites in structural automotive applications?

We have witnessed solid growth in the use of plastics and composites over the last decade. With the increased attention on fuel efficiency, there is no doubt that this trend will continue. More and more low-volume niche vehicles and highly energy-efficient "green" vehicles will likely have an increasing amount of composite content as crashworthiness design requirements are facilitated. Mass use for automotive applications will require some significant innovations in manufacturing methods to bring down the current high production costs.

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