Deployable structures made from ultra-thin composite materials can be folded elastically and are able to self-deploy by releasing the stored strain energy. Their lightness, low cost due to smaller number of components, and friction insensitive behaviour are key attractions for space applications. This dissertation presents a design methodology for lightweight composite booms with multiple tape-spring hinges. The whole process of folding and deployment of the tape-spring hinges under both quasi-static and dynamic loading has been captured in detail through finite element simulations, starting from a micro-mechanical model of the laminate based on the measured geometry and elastic properties of the woven tows. A stress-resultant based six-dimensional failure criterion has been developed for checking if the structure would be damaged. A detailed study of the quasi-static folding and deployment of a tape-spring hinge made from a two-ply plain-weave laminate of carbon-fibre reinforced plastic has been carried out. A particular version of this hinge was constructed and its moment-rotation profile during quasi-static deployment was measured. Folding and deployment simulations of the tape-spring hinge were carried out with the commercial finite element package Abaqus/Explicit, starting from the as-built, unstrained structure. The folding simulation includes the effects of pinching the hinge in the middle to reduce the peak moment required to fold it. The deployment simulation fully captures both the steady-state moment part of the deployment and the final snap back to the deployed configuration. An alternative simulation without pinching the hinge provides an estimate of the maximum moment that could be carried by the hinge during operation. This moment is about double the snap-back moment for the particular hinge design that was considered. The dynamic deployment of a tape-spring hinge boom has been studied both experimentally and by means of detailed finite-element simulations. It has been shown that the deployment of the boom can be divided into three phases: deployment; latching, which may involve buckling of the tape springs and large rotations of the boom; and vibration of the boom in the latched configuration. The second phase is the most critical as the boom can fold backwards and hence interfere with other spacecraft components. A geometric optimisation study was carried out by parameterising the slot geometry in terms of slot length, width and end circle diameter. The stress-resultant based failure criterion was then used to analyse the safety of the structure. The optimisation study was focused on finding a hinge design that can be folded 180 degrees with the shortest possible slot length. Simulations have shown that the strains can be significantly reduced by allowing the end cross-sections to deform freely. Based on the simulations a failure-critical design and a failure-safe design were selected and experimentally verified. The failure-safe optimised design is six times stiffer in torsion, twice stiffer axially and stores two and a half times more strain energy than the previously considered design. Finally, an example of designing a 1 m long self-deployable boom that could be folded around a spacecraft has been presented. The safety of this two-hinge boom has been evaluated during both stowage and dynamic deployment. A safe design that latches without any overshoot was selected and validated by a dynamic deployment experiment.

The strive for lower fuel consumption and downsizing in the automotive industry has led to the use of alternative high performance materials, such as fibre composites. Designing chassis components with composite materials require accurate simulation models in order to capture the behaviour in car crashes. By simplifying the development process of a B-pillar with a new dynamic test method, composite material products could reach the market faster. The setup has to predict a cars side impact crash performance by only testing the B-pillar in a component based environment. The new dynamic test method with more realistic behaviour gives a better estimation of how the B-pillar, and therefore the car, will perform in a full-scale car side impact test. With the new improved tool for the development process, the search for a lighter product with better crash worthiness is done by optimising a steel carbon fibre hybrid structure in the B-pillar. The optimisation includes different carbon fibre materials, composite laminate lay-up and stiffness analysis. By upgrading simulation models with new material and adhesive representation physical prototypes could be built to verify the results. Finally the manufactured steel carbon fibre hybrid B-pillar prototypes were tested in the developed dynamic test method for a comparison to the steel B-pillar. The hybrid B-pillars perform better than the reference steel B-pillar in the dynamic tests also being considerably lighter. As a final result a hybrid B-pillar is developed that will decrease fuel consumption and meet the requirements of any standardized side impact crash test. / Strävan efter lägre bränsleförbrukning och minimalistiskt tänkande inom bilindustrin har lett till användning av alternativa högpresterande material, såsom fiberkompositer. Vid design av chassi-komponenter utav kompositer krävs noggranna simuleringsmodeller för att fånga upp bilens beteende vid en krock. Genom att förenkla utvecklingsprocessen för en B-stolpe med en ny dynamisk testmetod kan produkter bestående av fiberkompositer nå marknaden snabbare. Provuppställningen skall förutse bilens prestanda vid ett sidokrocktest genom att endast testa B-stolpen i en komponentbaserad miljö. Den nya dynamiska testmetoden med ett mer realistiskt beteende skall ge en bättre uppskattning om hur B-stolpen, och därmed bilen, kommer att prestera i ett fullskaligt sidokrocktest. Med utvecklingsprocessens nya förbättrade verktyg kan strävan mot lättare produkter med bättre krocksäkerhet utvecklas genom optimering av en hybrid B-stolpe i stål och kolfiber. Optimeringen innefattar olika kolfibermaterial, laminatvarianter och styvhetsanalyser. Genom att uppgradera simuleringsmodeller med nya material och adhesiva metoder kunde fysiska prototyper tillverkas för att verifiera resultaten. Slutligen testades de tillverkade prototyperna utav stål och kolfiber i den nyutvecklade dynamiska testmetoden för jämförelse mot den ursprungliga stål B-stolpen. Hybrid B-stolparna presterade bättre än referensstolpen utav stål i de dynamiska provningarna och är samtidigt betydligt lättare. Det slutgiltigt resultatet är en utvecklad hybrid B-stolpe som både ger minskad bränsleförbrukningen och uppfyller kraven för ett standardiserat sidokrocktest.