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