Commenced in January 2007
Frequency: Monthly
Edition: International
Paper Count: 30855
Research of the Load Bearing Capacity of Inserts Embedded in CFRP under Different Loading Conditions

Authors: F. Pottmeyer, M. Weispfenning, K. A. Weidenmann


Continuous carbon fiber reinforced plastics (CFRP) exhibit a high application potential for lightweight structures due to their outstanding specific mechanical properties. Embedded metal elements, so-called inserts, can be used to join structural CFRP parts. Drilling of the components to be joined can be avoided using inserts. In consequence, no bearing stress is anticipated. This is a distinctive benefit of embedded inserts, since continuous CFRP have low shear and bearing strength. This paper aims at the investigation of the load bearing capacity after preinduced damages from impact tests and thermal-cycling. In addition, characterization of mechanical properties during dynamic high speed pull-out testing under different loading velocities was conducted. It has been shown that the load bearing capacity increases up to 100% for very high velocities (15 m/s) in comparison with quasi-static loading conditions (1.5 mm/min). Residual strength measurements identified the influence of thermal loading and preinduced mechanical damage. For both, the residual strength was evaluated afterwards by quasi-static pull-out tests. Taking into account the DIN EN 6038 a high decrease of force occurs at impact energy of 16 J with significant damage of the laminate. Lower impact energies of 6 J, 9 J, and 12 J do not decrease the measured residual strength, although the laminate is visibly damaged - distinguished by cracks on the rear side. To evaluate the influence of thermal loading, the specimens were placed in a climate chamber and were exposed to various numbers of temperature cycles. One cycle took 1.5 hours from -40 °C to +80 °C. It could be shown that already 10 temperature cycles decrease the load bearing capacity up to 20%. Further reduction of the residual strength with increasing number of thermal cycles was not observed. Thus, it implies that the maximum damage of the composite is already induced after 10 temperature cycles.

Keywords: Dynamic Loading, Composite, Impact, Joining, thermal loading, inserts, residual strength

Digital Object Identifier (DOI):

Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1375


[1] P. P. Camanho; M. Lambert: A design methodology for mechanically fastened joints in laminated composite materials. In: Composites Science and Technology 66 (15), S. 3004–3020, 2006.
[2] I. Eriksson: On the Bearing Strength of Bolted Graphite/Epoxy Laminates. In: Journal of Composite Materials 24 (12), S. 1246–1269, 1990.
[3] Yi Xiao; Takashi Ishikawa: Bearing strength and failure behavior of bolted composite joints (part I. Experimental investigation). In: Composites Science and Technology 65 (7-8), S. 1022–1031, 2005.
[4] B. Kolesnikov; L. Herbeck; A. Fink: CFRP/titanium hybrid material for improving composite bolted joints. In: Composite Structures 83 (4), S. 368–380, 2008.
[5] J. Gebhardt; J. Fleischer: Experimental Investigation and Performance Enhancement of Inserts in Composite Parts. In: Procedia CIRP 23, S. 7–12, 2014.
[6] B. Ferret; C. Anduze; C. Nardari: Metal inserts in structural composite materials manufactured by RTM. In: Composites Part A (29), S. 693–700, 1998.
[7] C. Hopmann; Fecher, M. L., Lineman, L.; R. Bastian; T. Gries; A. Schnabel; C. Greb: Comparison of the properties of Onserts and Inserts for a high volume production of structural composite parts. In: Journal of Plastics Technology 9 (4), S. 179–206, 2013.
[8] J. Fleischer; J. Gebhardt: Experimental Investigation of Metal Inserts Embedded in Composite Parts Manufactured by the RTM Process. 13th Japan International SAMPE Symposium and Exhibition,Nagoya, Japan, 2013.
[9] Marcus Schwarz; Michael Magin; Carsten Peil; Helmut Schürmann: Thin-walled FRP-laminates and local bending moments - incompatible or solvable by a skillful design? Internationale Tagung für Verstärkte Kunststoffe und Duroplastische Formmasse, Baden-Baden, Germany, 2004.
[10] Johannes Gebhardt; Florentin Pottmeyer; Jürgen Fleischer; Kay Weidenmann: Characterization of Metal Inserts Embedded in Carbon Fiber Reinforced Plastics. In: MSF 825-826, S. 506–513, 2015.
[11] Florentin Pottmeyer; Julia Bittner; Pascal Pinter; Kay André Weidenmann: In-situ CT damage analysis of metal inserts embedded in carbon fiber reinforced plastics. Submitted. In: NDT & E International 2016.
[12] Norihiko Taniguchi; Tsuyoshi Nishiwaki; Hiroyuki Kawada: Tensile strength of unidirectional CFRP laminate under high strain rate. In: Advanced Composite Materials 16 (2), S. 167–180, 2007.
[13] J. Harding; L. M. Welsh: A tensile testing technique for fibre-reinforced composites at impact rates of strain. In: J Mater Sci 18 (6), S. 1810–1826, 1983.
[14] Bing Wang; Lin-Zhi Wu; Li Ma; Ji-Cai Feng: Low-velocity impact characteristics and residual tensile strength of carbon fiber composite lattice core sandwich structures. In: Composites Part B: Engineering 42 (4), S. 891–897, 2011.
[15] G. Caprino; R. Teti: Impact and post-impact behavior of foam core sandwich structures. In: Composite Structures 29 (1), S. 47–55, 1994.
[16] V. J. Hawyes; P. T. Curtis; C. Soutis: Effect of impact damage on the compressive response of composite laminates. In: Composites Part A: Applied Science and Manufacturing 32 (9), S. 1263–1270, 2001.
[17] O. Ishai; A. Shragai: Effect of impact loading on damage and Residual Compressive Strength of CFRP laminated beams. In: Composite Structures 14 (4), S. 319–337, 1990.
[18] G. Caprino: Residual Strength Prediction of Impacted CFRP Laminates. In: Journal of Composite Materials 18 (6), S. 508–518, 1984.
[19] S. Sánchez-Sáez; E. Barbero; C. Navarro: Compressive residual strength at low temperatures of composite laminates subjected to low-velocity impacts. In: Composite Structures 85 (3), S. 226–232, 2008.
[20] T. Shimokawa; H. Katoh; Y. Hamaguchi; S. Sanbongi; H. Mizuno; H. Nakamura et al.: Effect of Thermal Cycling on Microcracking and Strength Degradation of High-Temperature Polymer Composite Materials for Use in Next-Generation SST Structures. In: Journal of Composite Materials 36 (7), S. 885–895, 2002.
[21] Jonas Wilkening; Florentin Pottmeyer; Kay André Weidenmann: Research on the interfering effect of metal inserts in carbon fiber reinforced plastics manufactured by the RTM process. 17th European Conference on Composite Materials, Munich, Germany, 2016.
[22] Yasushi Miyano; Masayuki Nakada; Hiroshi Kudoh; Rokuro Muki: Prediction of tensile fatigue life under temperature environment for unidirectional CFRP. In: Advanced Composite Materials 8 (3), S. 235–246, 1999.
[23] Patricia P. Parlevliet; Harald E.N. Bersee; Adriaan Beukers: Residual stresses in thermoplastic composites—A study of the literature—Part I. Formation of residual stresses. In: Composites Part A: Applied Science and Manufacturing 37 (11), S. 1847–1857, 2006.
[24] Kum Cheol Shin; Jung Ju Lee: Effects of thermal residual stresses on failure of co-cured lap joints with steel and carbon fiber–epoxy composite adherends under static and fatigue tensile loads. In: Composites Part A: Applied Science and Manufacturing 37 (3), S. 476–487, 2006.
[25] Hak Sung Kim; Sang Wook Park; Dai Gil Lee: Smart cure cycle with cooling and reheating for co-cure bonded steel/carbon epoxy composite hybrid structures for reducing thermal residual stress. In: Composites Part A: Applied Science and Manufacturing 37 (10), S. 1708–1721, 2006.
[26] T. A. Bogetti; J. W. Gillespie: Process-Induced Stress and Deformation in Thick-Section Thermoset Composite Laminates. In: Journal of Composite Materials 26 (5), S. 626–660, 1992.
[27] John F. Timmerman; Matthew S. Tillman; Brian S. Hayes; James C. Seferis: Matrix and fiber influences on the cryogenic microcracking of carbon fiber/epoxy composites. In: Composites Part A: Applied Science and Manufacturing 33 (3), S. 323–329, 2002.
[28] Lucas F. M. da Silva; R. D. Adams: Stress-free temperature in a mixed-adhesive joint. In: Journal of Adhesion Science and Technology 20 (15), S. 1705–1726, 2006.
[29] J. Ju: Characterization of Microcrack Development in BMI-Carbon Fiber Composite under Stress and Thermal Cycling. In: Journal of Composite Materials 38 (22), S. 2007–2024, 2004.
[30] L. J. Hart-Smith: Adhesive-bonded double-lap joints. Hg. v. NASA CR-112235. NASA. Houston, Texas, 1973.
[31] F. S. Jumbo; I. A. Ashcroft; A. D. Crocombe; M.M Abdel Wahab: Thermal residual stress analysis of epoxy bi-material laminates and bonded joints. In: International Journal of Adhesion and Adhesives 30 (7), S. 523–538, 2010.
[32] Y. Yu; I. A. Ashcroft; G. Swallowe: An experimental investigation of residual stresses in an epoxy–steel laminate. In: International Journal of Adhesion and Adhesives 26 (7), S. 511–519, 2006.