Ply Failure Calculator

Introduction

This file containts functions to determine the if the loaded laminate fails acording to one of the following failure criteria:

  • Max stress
  • Tsai-Wu
  • Tsai-Hill

Note

An extension is planned for the Puck critria and some ‘inverse’ method. These inverse methods will return a scaling factor of which the load can be multiplied with before failure is reached.

Routines

Calculate the failure (critera) of the composite material.

A.J.J. Lagerweij COHMAS Mechanical Engineering KAUST 2020

failure.max_stress(stress, sl_max, sl_min, st_max, st_min, tlt_max)

Compare stresses to the max stress criteria, returns which layers failed.

Failure stresses and ply stresses must be in the same orientation.

Warning

This method does not take interaction of stresses in different directions in account.

Parameters:
  • stress (list) – A list containing the stress vector of the bottom, middle and top of each layer.
  • sl_max (float) – Maximum tensile stress in longitudional direction.
  • sl_min (float) – Maximum compressive stress in longitudional direction.
  • st_max (float) – Maximum tensile stress in transverse direction.
  • st_min (float) – Maximum compressive stress in transverse direction.
  • tlt_max (float) – Maximum shear stress in material axis system.
Returns:

pass – True if the load was below the maximum allowables.
Return type:

bool
failure.tsai_hill(stress, sl_max, sl_min, st_max, st_min, tlt_max)

Test wether the stresses are outside the plane stress Tsai-Hill criteria.

Failure stresses and ply stresses must be in the same orientation. The method is an extension of the von Mieses stress criteria.

Parameters:
  • stress (list) – A list containing the stress vector of the bottom, middle and top of each layer.
  • sl_max (float) – Maximum tensile stress in longitudional direction.
  • sl_min (float) – Maximum compressive stress in longitudional direction.
  • st_max (float) – Maximum tensile stress in transverse direction.
  • st_min (float) – Maximum compressive stress in transverse direction.
  • tlt_max (float) – Maximum shear stress in material axis system.
Returns:

pass – True if the load was below the maximum allowables.
Return type:

bool
failure.tsai_wu(stress, sl_max, sl_min, st_max, st_min, tlt_max)

Test wether the stresses are outside the plane stress Tsai-Wu criteria.

Failure stresses and ply stresses must be in the same orientation.

Warning

This criteria is a bad approximation for compression failure.

Parameters:
  • stress (list) – A list containing the stress vector of the bottom, middle and top of each layer.
  • sl_max (float) – Maximum tensile stress in longitudional direction.
  • sl_min (float) – Maximum compressive stress in longitudional direction.
  • st_max (float) – Maximum tensile stress in transverse direction.
  • st_min (float) – Maximum compressive stress in transverse direction.
  • tlt_max (float) – Maximum shear stress in material axis system.
Returns:

pass – True if the load was below the maximum allowables.
Return type:

bool