Experimental and numerical investigation on the open-hole compressive strength of AFP composites containing gaps and overlaps

Laminated composite structures manufactured via the automated fiber placement process inherently contain process defects know as gaps and overlaps. These defects raise concerns when they are located on or near holes intended for mechanical fastening. This investigation attempts to predict the effect of automated fiber placement-generated defects on the open-hole compression strength by combining both experimental tests and numerical simulation. Tested open-hole compression specimens containing gaps and overlaps oriented at 0° or 90° and centered on or shifted near the hole show that, depending on their location, the gaps and overlaps may have negative, negligible, or positive effects on the open-hole compression strength. The better than expected effects are compatible with microscopic observations that clearly show the rearrangement of the plies during the consolidation process, which prevent the formation of deleterious discontinuities. Incorporating these observations in a numerical model, which simulates gaps and overlaps embedded inside the composite laminates, and applying a progressive failure analysis, confirms that the effects of automated fiber placement defects depend as much on their type as on their location relative to the hole center. Finally, the results obtained from a parametric study provided further explanation on the effects of automated fiber placement defects on the failure strength of perforated composite laminates.

[1]  P. D. Soden,et al.  Predicting failure in composite laminates: the background to the exercise , 1998 .

[2]  Fu-Kuo Chang,et al.  Post-Failure Analysis of Bolted Composite Joints in Tension or Shear-Out Mode Failure , 1987 .

[3]  M. Hojo,et al.  Finite-element modeling of initial matrix failure in CFRP under static transverse tensile load , 2001 .

[4]  Venkata M. K. Akula,et al.  Review of Degradation Models for Progressive Failure Analysis of Fiber Reinforced Polymer Composites , 2009 .

[5]  Damiano Pasini,et al.  Experimental study of the effect of automated fiber placement induced defects on performance of composite laminates , 2011 .

[6]  P. D. Soden,et al.  A comparison of the predictive capabilities of current failure theories for composite laminates: additional contributions , 2004 .

[7]  Mark W. Hilburger,et al.  Progressive failure analyses of compression-loaded composite curved panels with and without cutouts , 2004 .

[8]  Zafer Gurdal,et al.  A Theoretical Model to Study the Influence of Tow-drop Areas on the Stiffness and Strength of Variable-stiffness Laminates , 2009 .

[9]  Fu-Kuo Chang,et al.  Composite panels containing multiple through-the-width delaminations and subjected to compression. Part I: Analysis , 1995 .

[10]  Bijan Shirinzadeh,et al.  Fabrication process of open surfaces by robotic fibre placement , 2004 .

[11]  Z. Hashin.  Failure Criteria for Unidirectional Fiber Composites , 1980 .

[12]  Z. Gürdal,et al.  Variable stiffness composite panels : Effects of stiffness variation on the in-plane and buckling response , 2008 .

[13]  Brian Tatting,et al.  Tow-Placement Technology and Fabrication Issues for Laminated Composite Structures , 2005 .

[14]  N. Gascons,et al.  Variable-stiffness composite panels: Defect tolerance under in-plane tensile loading , 2014 .

[15]  Damiano Pasini,et al.  Defect layer method to capture effect of gaps and overlaps in variable stiffness laminates made by Automated Fiber Placement , 2013 .

[16]  P. D. Soden,et al.  A COMPARISON OF THE PREDICTIVE CAPABILITIES OF CURRENT FAILURE THEORIES FOR COMPOSITE LAMINATES , 1998 .

[17]  Pedro P. Camanho,et al.  Stress analysis and strength prediction of mechanically fastened joints in FRP: A review , 1997 .

[18]  P. D. Soden,et al.  A COMPARISON OF THE PREDICTIVE CAPABILITIES OF CURRENT FAILURE THEORIES FOR COMPOSITE LAMINATES, JUDGED AGAINST EXPERIMENTAL EVIDENCE , 2002 .

[19]  F. Chang,et al.  A Progressive Damage Model for Laminated Composites Containing Stress Concentrations , 1987 .

[20]  K. Potter,et al.  The engineering aspects of automated prepreg layup: History, present and future , 2012 .

[21]  Carroll Grant,et al.  Automated processes for composite aircraft structure , 2006, Ind. Robot.

[22]  Samuel T. IJsselmuiden,et al.  Design of variable-stiffness composite panels for maximum buckling load , 2009 .

[23]  Levon Minnetyan,et al.  Prediction of composite laminate fracture: micromechanics and progressive fracture , 1998 .

[24]  Dawn C. Jegley,et al.  Automated Finite Element Analysis of Elastically-Tailored Plates , 2013 .

[25]  Masaki Hojo,et al.  Failure behavior of an epoxy matrix under different kinds of static loading , 2001 .

[26]  Luke Everett Turoski,et al.  Effects of manufacturing defects on the strength of toughened carbon/epoxy prepreg composites , 2000 .

[27]  Rodney S. Thomson,et al.  Review of methodologies for composite material modelling incorporating failure , 2008 .

[28]  P. D. Soden,et al.  A further assessment of the predictive capabilities of current failure theories for composite laminates: comparison with experimental evidence , 2004 .

[29]  Lorenzo Iannucci,et al.  Physically-based failure models and criteria for laminated fibre-reinforced composites with emphasis on fibre kinking: Part I: Development , 2006 .

[30]  Damiano Pasini,et al.  A comparative study of metamodeling methods for the design optimization of variable stiffness composites , 2014 .

[31]  Damiano Pasini,et al.  Optimization of variable stiffness composites with embedded defects induced by Automated Fiber Placement , 2014 .

[32]  Fu-Kuo Chang,et al.  Composite panels containing multiple through-the-width delaminations and subjected to compression. Part II: Experiments & verification , 1995 .