Source code for desicos.abaqus.imperfections.ffi

from __future__ import absolute_import

import numpy as np

from desicos.logger import warn
from .imperfection import Imperfection

[docs]class FFI(Imperfection): r"""Fiber Fraction Imperfection Thickness variations are generally caused by a varying amount of matrix, while the amount of fibers remains constant. Thus, the actual fiber volume fraction is higher in thinner sections of the material. This imperfection aims to include that effect in the model, by adjusting the material properties. ===================== ================================================== Attributes Description ===================== ================================================== nominal_vf ``float``, nominal fiber volume fraction E_matrix ``float``, Young's modulus of the matrix material nu_matrix ``float``, Poisson's ratio of the matrix material use_ti ``bool``, if ``True``, create varying material properties according to the thickness imperfection data (if present). global_sf ``float`` or ``None``, global scaling factor to apply to the material thickness. Set to ``None`` to disable. The global scaling may be overridden by a thickness imperfection, if ``use_ti`` (see above) is ``True``. created ``bool``, ``True`` after the imperfection has been created. ===================== ================================================== """ def __init__(self, nominal_vf, E_matrix, nu_matrix, use_ti, global_sf=None): super(FFI, self).__init__() self.nominal_vf = nominal_vf self.E_matrix = E_matrix self.nu_matrix = nu_matrix self.use_ti = use_ti self.global_sf = global_sf = 'FFI' self.xaxis = 'scaling_factor' self.xaxis_label = 'Global thickness scaling factor, -' self.created = False @property def scaling_factor(self): return 1.0 if self.global_sf is None else self.global_sf def rebuild(self): if self.global_sf is not None: = 'FFI_SF_%05d' % (int(round(100*self.global_sf)))
[docs] def calc_amplitude(self): """Calculates the imperfection amplitude Amplitude measured as the biggest thickness difference between the actual and nominal layup thickness of the Cone/Cylinder, considering only the layups that have this imperfection applied. .. note:: Must be called from Abaqus. Returns ------- max_amp : float Maximum absolute imperfection amplitude. """ cc = self.impconf.conecyl max_amp = 0 cc_total_t = sum(cc.plyts) if self.global_sf is not None: max_amp = abs(self.global_sf - 1.0) * cc_total_t if self.use_ti: from abaqus import mdb part = mdb.models[cc.model_name].parts[cc.part_name_shell] for layup in part.compositeLayups.values(): if not layup.suppressed: layup_t = sum(p.thickness for p in layup.plies.values()) max_amp = max(max_amp, abs(layup_t - cc_total_t)) self.amplitude = max_amp return self.amplitude
[docs] def calc_scaled_laminaprop(self, laminaprop, scaling_factor): """Calculate material properties of a lamina with a scaled thickness. Calculates the new lamina properties, if a given material (lamina) is scaled in thickness by a given factor. The new material properties are calculated from the properties of the fiber and the matrix, using the composition rule (for E11 and nu12) and the corrected composition rule (for E22, G12, G13 and G23). The matrix properties are to be supplied by the user. The fiber properties are calculated based on the original (nominal) lamina properties, using the inverse of the respective composition rule. Parameters ---------- laminaprop : tuple Material properties (E11, E12, nu12, G12, G13, G23) of the lamina at the nominal thickness scaling_factor : float Scaling factor that is to be applied to the ply thickness. The total amount of fibers is assumed to remain constant, thus the actual fiber volume fraction is inversely proportional to this scaling factor. Returns ------- new_laminaprop : tuple Lamina properties of the lamina with a scaled thickness """ assert len(laminaprop) == 6 E_m = float(self.E_matrix) nu_m = float(self.nu_matrix) G_m = E_m / (2.*(1.+nu_m)) vf_nom = float(self.nominal_vf) vf = vf_nom / scaling_factor if not (0. < vf < 1.): raise ValueError(('Invalid scaling factor {0:.2f} for Fiber' + 'Fraction Imperfection, resulting fiber volume fraction' + ' ({1:.2f}) is out of range 0..1)').format(scaling_factor, vf)) # Composition rule to obtain material properties, # based on fiber and matrix data # There are two different rules, one for longitudinal properties # (E11, nu12) and one for transversal props (E22, G12, G13, G23) def compL(X_f, X_m): return vf*X_f + (1 - vf)*X_m def compT(X_f, X_m): return X_m / (1 - np.sqrt(vf)*(1 - X_m/X_f)) comp_rule = (compL, compT, compL, compT, compT, compT) # Inverse composition rule to obtain fiber properties, # based on nominal laminate properties and matrix data def invL(X_nom, X_m): return (X_nom - (1 - vf_nom)*X_m) / vf_nom def invT(X_nom, X_m): return X_m*np.sqrt(vf_nom) / (X_m/X_nom - (1 - np.sqrt(vf_nom))) inv_comp_rule = (invL, invT, invL, invT, invT, invT) matrix_prop = (E_m, E_m, nu_m, G_m, G_m, G_m) fiber_prop = tuple(f(X_nom, X_m) for f, X_nom, X_m in zip(inv_comp_rule, laminaprop, matrix_prop)) new_laminaprop = tuple(f(X_f, X_m) for f, X_f, X_m in zip(comp_rule, fiber_prop, matrix_prop)) DEBUG_STRING = 'E11={0:.2f}, E22={1:.2f}, nu12 = {2:.2f},' +\ ' G12={3:.2f}, G13={4:.2f}, G23={5:.2f}' to_check = [(laminaprop, 'nominal laminate'), (matrix_prop, 'matrix'), (fiber_prop, 'calculated fiber'), (new_laminaprop, 'imperfect laminate')] for prop, name in to_check: if not (all(x > 0 for x in prop) and prop[2] < 0.5): mat_str = DEBUG_STRING.format(*prop) raise ValueError(('One or more invalid value(s) for {0}' + ' properties:\n{1}').format(name, mat_str)) return new_laminaprop
def _update_material(self, suffix, scaling_factor): from abaqus import mdb cc = self.impconf.conecyl mod = mdb.models[cc.model_name] warned = set() for name, laminaprop in zip(cc.laminapropKeys, cc.laminaprops): if len(laminaprop) == 6: new_laminaprop = self.calc_scaled_laminaprop(laminaprop, scaling_factor) else: if name not in warned: warn(('Invalid number of lamina properties for material' + '{0}, or material is isotropic. Fiber Fraction' + ' Imperfection is not applied.').format(name)) warned.add(name) new_laminaprop = laminaprop new_mat = mod.Material(name=(name + suffix), objectToCopy=mod.materials[name]) new_mat.elastic.setValues(table=(new_laminaprop,))
[docs] def create(self): """Actually create the imperfection .. note:: Must be called from Abaqus. """ from abaqus import mdb from desicos.abaqus.abaqus_functions import modify_composite_layup cc = self.impconf.conecyl part = mdb.models[cc.model_name].parts[cc.part_name_shell] if self.global_sf is not None: MAT_SUFFIX = '_scaled' self._update_material(MAT_SUFFIX, self.global_sf) def modify_mat_thick(index, kwargs): kwargs['thickness'] = cc.plyts[index] * self.global_sf kwargs['material'] = cc.laminapropKeys[index] + MAT_SUFFIX return kwargs modify_composite_layup(part, 'CompositePlate', modify_mat_thick) self.update_after_tis() self.created = True
[docs] def update_after_tis(self): """Call this function after the thickness imperfection(s) are applied, to modify the material properties as well, if needed. """ if not self.use_ti: return from abaqus import mdb from desicos.abaqus.abaqus_functions import modify_composite_layup cc = self.impconf.conecyl part = mdb.models[cc.model_name].parts[cc.part_name_shell] for layup_name in part.compositeLayups.keys(): if layup_name.startswith('CLayup_'): layup = part.compositeLayups[layup_name] thickness = sum(p.thickness for p in layup.plies.values()) scaling_factor = thickness / sum(cc.plyts) suffix = layup_name[-6:] self._update_material(suffix, scaling_factor) def modify_material(index, kwargs): kwargs['material'] = cc.laminapropKeys[index] + suffix return kwargs modify_composite_layup(part, layup_name, modify_material)