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978-3-8439-3252-3, Reihe Ingenieurwissenschaften
Grenzflächenphänomene metallisch z-verstärkter Kohlenstofffaserverbundverbindungen (Band 38)
132 Seiten, Dissertation Technische Universität München (2017), Softcover, A5
An assessment of interfacial phenomena acting between a titanium/stainless steel interleaving z-reinforcing sheet and the surrounding carbon fiber reinforced polymer (CFRP) is provided. Means of surface pretreatment were chosen to study on the reciprocal impact of the exposure to a hot/wet environment (70°°C, 85 % RH) on mechanical and chemical adhesion properties. Insights derived from mechanical tests on two levels constitute a basic understanding of failure behavior and delamination resistance of such reinforced laminates and joints. A bridging law was established to describe the functional relationship between traction forces and crack opening displacement on a single pin level. On this basis, fracture toughness was assessed on a co-bonded beam level under Mode I and Mode II loading conditions.
Surface analyses through scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS) indicate adhesion properties to be determined by surface morphology (mechanical adhesion) and chemistry (chemisorption). However, frictional pullout of the spike off the laminate is dominated by the morphology size, provided on a micro- and nanoscale. Test results further suggest stiffness prior to debonding of the spike to determine delamination resistance on a joint level. Curing cycle induced thermal residual stresses due to laminate’s and metal’s CTE’s mismatch as well as laminate’s swelling post moisture ingress have a major impact on the system rigidity. Hence, introduction of titanium reinforcements featuring a laser induced nanostructured oxide morphology lead to superior fracture toughness, even increased post hot/wet conditioning.