The influence of processing variables on the energy absorption of composite tubes

Abstract The aim of this work is to quantify the effect of process-related parameters on the level of specific energy absorption (SEA). This study comprises two sections: the first studies the effect of variable binder levels in the part (0–10% based on equivalent fibre mass). Highly soluble polyester powder binder is added to the resin to simulate the resin state near the end of injection and no binder is incorporated in the preform. The aim for the second part is to study the effect of processing variables on the level of voids in the composite and subsequently characterise the effect of void level on the energy absorption of the parts. Two thermosetting composite materials are examined; a continuous filament random mat (CoFRM) and a non-crimp fabric (NCF) at volume fractions of 22 and 38%, respectively. The parts moulded are generic tubular energy absorbing structures with double cantilever beam (DCB) and in-plane tensile and compressive specimens as secondary tests. An unsaturated polyester resin developed for automotive RTM applications is used for all parts. Mode-I fracture toughness shows significant changes with binder content, however, the SEA of the composite tube is observed to be very tolerant of binder level. Three processing regimes were used yielding void levels between ∼0 and over 10%. The SEA levels for both materials are seen to be tolerant of high void levels allowing potential cost reduction through rapid processing.

[1]  B. Gebart,et al.  Void Formation in RTM , 1993 .

[2]  J. Whitney,et al.  Stress Fracture Criteria for Laminated Composites Containing Stress Concentrations , 1974 .

[3]  K. Jayaraman,et al.  Dynamics of binder displacement in liquid molding , 1996 .

[4]  Chris D. Rudd,et al.  The effect of interlaminar toughening strategies on the energy absorption of composite tubes , 2004 .

[5]  Kenneth J. Bowles,et al.  Void Effects on the Interlaminar Shear Strength of Unidirectional Graphite-Fiber-Reinforced Composites , 1992 .

[6]  Andrew C. Long,et al.  Liquid Moulding Technologies , 1997 .

[7]  W. Young,et al.  Study on the Pre-Heated Temperatures and Injection Pressures of the RTM Process , 1994 .

[8]  Quentin P. V. Fontana.  Speed and Temperature Effects in the Energy Absorption of Axially Crushed Composite Tubes , 1990 .

[9]  Mirabel Cerqueira Rezende,et al.  The influence of porosity on the interlaminar shear strength of carbon/epoxy and carbon/bismaleimide fabric laminates , 2001 .

[10]  Paul J. Hogg,et al.  The relative effects of through-thickness properties and fibre orientation on energy absorption by continuous fibre composites , 1999 .

[11]  J. Eisenmann,et al.  Macroscopic Fracture Mechanics of Advanced Composite Materials , 1971 .

[12]  L. Hourng,et al.  Study on void formation in resin transfer molding , 1998 .

[13]  Puhui Chen,et al.  Prediction of the strength of notched fiber-dominated composite laminates , 2001 .

[14]  Effect of resin formulation on crash energy absorbing composite structures made by RTM , 2002 .

[15]  Chris D. Rudd,et al.  Effect of resin properties and processing parameters on crash energy absorbing composite structures made by RTM , 2003 .

[16]  J. Gillespie,et al.  Effects of thermoplastic preforming binder on the properties of S2-glass fabric reinforced epoxy composites , 2001 .

[17]  P. H. Thornton,et al.  Energy Absorption in Composite Structures , 1979 .

[18]  Woo Il Lee,et al.  Formation of microvoids during resin-transfer molding process , 2000 .