ALFRED PUCK’S THEORY ON FAILURE IN COMPOSITE MATERIALS
John WaldronComposite Materials- ME
7502
Worldwide Failure Exercise
Initially brainstormed at Saint Albans (UK) in 1991
Outlined lack of faith in current use of failure criteria in technology
Planned to assemble the most current failure theories and compare them to each other and to experimental data.
Introduction to Alfred Puck
1953: Engineering Degree at University of Applied Science- Hamburg
1979-1989: Professor of Design Technology- University of Kassel
Institute of Plastics Processing- Aachen
Prelude: Mohr’s Circle
Transformation of stress states
“Extreme normal stresses”
Mohr’s Circles of possible stress states
Mohr’s Circles and Fracture Envelope
Prelude: Hashin Differentiates
between positive applied normal stresses and negative applied normal stresses.
Implies that fracture angle can play a role in determining the mode of failure.
Identifies a fracture plane, but doesn’t follow through on finding it due to difficulty.
Martin Knops, “Analysis of Failure in Fiber-Polymer Laminates, the Theory of Alfred Puck”
Hashin’s Failure Criteria
Transformations
Physical Manifestations of Failure
Presence of stresses and micro-cracks
Debonding Inter-fiber form of failure Delamination Fiber Fracture
Puck’s IFF Modes of Failure
Mode A Direct Tensile Stress
Mode B Longitudinal Shear Stress
Creates Fracture Angle which leads to:
Mode C Wedge Effect
Master Fracture Body
Presence of Vector Fans Inclusion of longitudinal shear
stress to Mohr’s Fracture Envelope
Behavior of Contours Fracture Surface dependant on
stresses, inclination parameters and strength parameters
Martin Knops, Analysis of Failure in Fiber-Polymer Laminates- the Theory of Alfred Puck
Strength Parameters Physical Definitions
of Parameters
Numerical Meanings behind Parameters
Relation to Action Plane
Strength Parameter
R||t
R||c
R_|_t
R_|_c
R_|__|_
R_|_||
Fiber Fracture
IFF MODES: Introduction
IFF MODES: Pure Stress
Mode A
Mode B
IFF MODE C
Fracture Angle
Mode C
Degradation Factors
Physical Definition of Degradation Factor
Relevance of Degradation in IFF Modes of Failure
Single-Ply Break Analysis—Weakening Factor
Gradual Failure
Numerical Comparison
Puck compares to Tsai-Hill and Hashin
Material: E-Glass fiber/ LY556 plastic
All failure analyses done in MATHCAD
Material Properties
Material Property E-glass/LY556Axial Young’s Modulus (E1) 53,480 MPa
Transverse Young’s Modulus (E2) 17,700 MPa
Shear Modulus (G12) 5,830 MPa
Poisson’s Ratio (υ12) 0.278
Axial Tensile Strength (XT) 1140 MPa
Axial Compressive Strength (XC) -570 MPa
Transverse Tensile Strength (YT) 40 MPa
Transverse Compressive Strength (YC) -135 MPa
Ultimate Shear Strength (SC) 61 MPa
Comparison Results
Failure Theory (fE)
0° Ply
(fE)
45° Ply
(fE)
90° Ply
Tsai-Hill 0.031 1.414 1.804
Hashin (Fiber) 0.031 0.151 0.009
Hashin (Matrix) 0.009 1.415 1.802
Puck (Fiber) 0.15 0.092 0.024
Puck (Mode A) 0.0002 0.217 0.284
Alfalam Software
Previous Model: NOLI FRAN COLAM
Written in FORTRAN Alfalam is Excel-based and
contains few improvements over NOLI FRAN COLAM
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