@article{HoltmannspoetterCzarneckiFeuchtetal., author = {Holtmannsp{\"o}tter, Jens and Czarnecki, J{\"u}rgen von and Feucht, Florian and Wetzel, Michael and Gudladt, Hans Joachim and Hofmann, Timo and Meyer, J. C. and Niedernhuber, Michal}, title = {On the Fabrication and Automation of Reliable Bonded Composite Repairs}, series = {Journal of adhesion}, volume = {91}, journal = {Journal of adhesion}, number = {1-2}, publisher = {Taylor\&Francis}, doi = {10.1080/00218464.2014.896211}, pages = {39 -- 70}, abstract = {For structures made of carbon fiber-reinforced plastics (CFRP), fast, robust, and reliable repair technologies are mandatory for economical usage. In this paper, the authors explain their strategy and experiences. An automated process is proposed to achieve the challenging goals. A general overview on the origin, effects, and analysis of contaminants in CFRP structures and the relationship to the achievable strength of adhesive bonds are given. For the repair of composite structures using adhesive bonding, surface pretreatment is a key factor in terms of reliability and strength. Different surface treatment processes such as grinding, grit blasting, plasma and pulsed lasers treatments are discussed. Furthermore, the possibilities and technical implementation of an automated milling process for the repair of composite structures are presented. This change from manual production to automation tremendously improved the quality and duration of the repair and allows the creation of a uniform surface for adhesive bonding. Further integration of novel technologies is discussed and will further support and enhance the repair in the near future.}, language = {en} } @inproceedings{NiedernhuberEhrlichHoltmannspoetter, author = {Niedernhuber, Michal and Ehrlich, Ingo and Holtmannsp{\"o}tter, Jens}, title = {Fiber-Oriented Repair of Fiber Reinforced Plastics: Investigations on Tensile Specimens}, series = {4th Applied Research Conference - ARC 2014, 5th July 2014, Ingolstadt}, booktitle = {4th Applied Research Conference - ARC 2014, 5th July 2014, Ingolstadt}, editor = {Ziemann, Olaf and Mottok, J{\"u}rgen and Pforr, Johannes}, publisher = {Shaker}, address = {Aachen}, pages = {298 -- 302}, language = {en} } @article{NiedernhuberHoltmannspoetterEhrlich, author = {Niedernhuber, Michal and Holtmannsp{\"o}tter, Jens and Ehrlich, Ingo}, title = {Fiber-oriented repair geometries for composite materials}, series = {Composites, Part B}, volume = {94}, journal = {Composites, Part B}, doi = {10.1016/j.compositesb.2016.03.027}, pages = {327 -- 337}, abstract = {In this paper, the idea of fiber-oriented repair geometries for carbon fiber reinforced plastics (CFRP) is investigated. It considers the differing mechanical properties of unidirectional fiber reinforced material by excluding overlapping regions perpendicular to the fiber direction of the particular layer. A mechanical and numerical comparison of tensile strength of stepped joints with continuous step lengths per ply and stepped joints with reduced step lengths in plies with fiber orientation differing from load direction is performed. Finite element simulations show similar shear stresses. Mechanical tests of CFRP laminates with stepped joints show no significant deviation in tensile strength, in spite of a joint length reduction of nearly 40\%. This leads to the possibility of a significant reduction of repair area.}, language = {en} }